AGCO Automotive Corporation Vehicle Questions

Does AGCO ever run sales or specials?

The entire philosophy of AGCO is overall lowest cost, everyday. Every vehicle is thoroughly inspected and the overall lowest cost option is always suggested. This may or may not be the lowest priced service. Rather than price the experts at AGCO provide you with the lowest cost. In this way you trust AGCO to take care of your needs everyday.
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Does AGCO offer free vehicle inspections?

I think most people realize, there truly is nothing free. AGCO charges for the actual time we work on the vehicle, never more. A fair price for a professional and honest diagnosis.

Free inspections are based on the premise of getting people in the door. The cost of the inspection is then added back to the price of the work. We feel this is less than honest and encourages overselling. For instance, I would not wish to go to someone that only gets paid if they find something wrong.

A far more complete explanation can be found at How much is a diagnosis.
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How can I find an answer to a specific vehicle question on agcoauto.com?

The Vehicle Questions Category is designed just for that purpose. You can find a Tutorial on using the search function here or you can send an email with your question.
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How does AGCO price it’s work?

AGCO charges for the actual time the technician works on your vehicle. While this may sound like common sense, it is very unusual in the automotive business. Most shops charge based on a flat-rate guide. The guide give a time to perform a service, and that time is billed without regard to the time spent.

For example if the book says a task should take three hours, and the technician does it in two, the client is still billed for three. Some claim this is their reward for being efficient, but I feel over-billing is unjustifiable. Others say sometimes the job takes longer than book time and it balances out. I feel if that were the case why not just bill actual time?

In my opinion the system rewards rushing through the job and penalizes spending time to insure quality. The old adage, “That which is rewarded gets done,” may help to explain the general state of the auto repair business which so many find unacceptable.

A far more complete explanation can be found at Actual time billing.
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I am a non-smoker, and do not want anyone to smoke in my vehicle.

AGCO is a totally non-smoking facility. No smoking is allowed in the shop, client's vehicles or in the office areas. This presents no problem for our staff as we are all non-smokers as well.
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I notice AGCO works by appointment, can I also drop off my vehicle without an appointment?

Absolutely, you can drop off a vehicle at any time. We make appointments for the day and guarantee your vehicle will be worked on the day of the appointment. We do this by turning down other clients for a specific day once we reach capacity for that day. This is very popular and for that reason appointments are often taken up a week in advance.

If you do not necessarily have to have the vehicle looked at on the day you drop it, we can work it in between appointments. This may take a few days but is often a lot sooner. If we get ahead of schedule or someone cancels an appointment any vehicles left with us are put into the first available spot.
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My automatic transmission needs service, does AGCO do transmission service?

YES! AGCO is equipped to service your automatic transmission properly. We replace the fluid with the factory specified type and where possible replace the filter. We never flush transmissions through the cooler lines or take short cuts that might damage your transmission.

A far more complete explanation can be found at Transmission Service.
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What are your hours of operation?

AGCO is open

Monday through Thursday
from 7:00 AM till 5:30 PM
and Friday from 7:00 AM till Noon.

AGCO also observes most State, Local and National Holidays, see Holidays for a listing.

A far more complete explanation can be found at Hours of operation.
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What breed of dog is Foxy, the AGCO greeter?

Foxy is a one of a kind pure bred, the first of the species [Mutt]

Her email address is Foxy
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What date was AGCO founded?

The official date is December 20, 1974, though the concepts and philosophies that would become AGCO were being worked on quite a bit earlier. A bad experience while working in another auto service facility prompted founder Louis Altazan to visualize a service facility quite different than any he could find.

Over the years the concepts have been refined but never altered. The basis will always be; fixed right the first time, delivered on time and at the price quoted. Coupled with extremely high quality service, we feel this will provide overall lowest cost of vehicle ownership which is our hallmark.
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What does the name AGCO stand for?

AGCO = Altazan Garage Company. Founded by Louis Altazan in 1974.
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What is overall lowest cost?

Overall lowest cost is a concept of considering factors other than just price, such as collateral expenses and how long the product or service last. The concept is widely used by professional purchasing agents to lower the cost of their clients. Many people make decisions based only on price and suffer much higher cost as a result.
An example might be cheap paint. The price is five dollars less a gallon, but it requires twice as much as better paint to get the same coverage. Four gallons are needed to do the job of two of the better brand. After a few years the cheap paint fades and peels. The better product give years of good service, looks better, is easier to clean and thus is much less expensive, overall.

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What is your phone number and why is AGCO not listed in the Yellow Pages?

Our phone number is (225) 291-6900.

AGCO chose several years ago to discontinue advertising in the Yellow Pages. While we constantly seek new clients, we feel our first priority is to provide the best service possible to our present clients.

We have a large Bold face listing in the white pages under AGCO Automotive Corporation.
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When does AGCO close for vacation?

All AGCO employees have three weeks paid vacation and we all take vacation as a team. The first week is in the Summer and is selected by common agreement of all employees.

The second week is always Thanksgiving week, from the Monday preceding the Holiday until the Friday following it.

The final week is always the week between Christmas and New Years.

A far more complete explanation can be found at AGCO Vacation.
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Which credit cards does AGCO accept?

We accept:

Visa
Mastercard
Discover
American Express

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Which Holidays does AGCO observe?

We feel allowing our personnel, time off to be with their families is a very important part of our total quality concept. For this reason AGCO observes all major holidays and some local ones as well. Please call for details (225) 291-6900.

A far more complete explanation as well as an interactive calendar showing hours, holidays and vacation can be found at AGCO Holidays.
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Why does AGCO close at Noon on Friday?

We have found that by allowing our staff time off to spend with their families, they are far more efficient and accurate in their work. Our four and a half day work week makes us attractive as an employer and allows us to retain our people and attract the best technicians. This is one reason for the extremely low turnover rate enjoyed by AGCO. Isn't it nice seeing the same faces year after year, when you need automotive service?
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Why does AGCO not quote prices on the phone?

One of the largest complaints against the auto repair trade is a lack of trust. Largely this stems from being quoted a price and then being charged another, usually much higher price. There are many places that use this tactic on a regular basis. The fact is, without knowing what is wrong with the vehicle there is no way to quote a price.

Instead, AGCO will perform a professional inspection, an accurate diagnosis and then give you an exact price, before any other work is done. The best part is we charge only for the actual time we spend checking the vehicle. No guess work, no deceitful practices, no surprises, just a great job, right the first time and at a fair price.

A far more complete explanation can be found at Prices on the phone.
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Air Condition/Heating

A few months ago, the blower on my car air conditioner quit working. The blower control module was replaced and it worked for two months. It quit again and the problem was again the blower control module. Now the module has failed again.

Blower control module failure can often be traced to excess current draw from the blower motor. As blower motors age, the current [in amps] required to turn them can increase. The excess amperage will destroy control modules and can burn wiring. Replacing the blower module is treating the symptom. The circuit should be tested for amperage draw and proper grounding. If amperage is too high, the motor or connection causing the problem should be replaced.
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After driving a while my air conditioner stops cooling. If I turn it off it will cool again after a while. I checked and the compressor is still turning when it stops cooling and the system is properly charged.

If the compressor is still turning and the system is properly charged, the most likely problem is the evaporator freezing. If the system has a cycle switch, I would first check that. Many AC compressors today do not have cycle switches and instead are variable displacement. They run all the time and vary compressor displacement to vary cooling. Adjustments are made based on the low side pressure. In such a system, if the compressor fails, it may not cut back and the system will freeze. Once the evaporator freezes, the system will stop blowing cool air, until it is allowed to thaw.
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After having the compressor replaced on my GM SUV, the rear unit cools well but the front is not as cool as it needs to be, any ideas?

If the system was working normally before the compressor failed, likely the problem is relating to refrigerant flow. GM uses an expansion valve to control the rear evaporator and an orifice tube to control the front. When compressors fail, there is often debris that enters the system. This debris can cause the expansion valve to malfunction. One possibility is this is causing unregulated flow to the rear core and inadequate cooling on the front.
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After replacing the battery, my air conditioner and heater controls no longer work. All air seems to blow from the defrost regardless of selector position?

On older vehicles with vacuum controlled mode doors, I would suspect a vacuum line may have been pulled off or broken when the battery was replaced. On newer vehicles with electronic actuators, disconnecting the battery can sometimes cause them to lose their memory of actuator position. When this happens the system may default to defrost. Make sure the ignition is off and disconnect the battery again, for several minutes. After reconnecting the battery, turn the ignition switch on, without starting the engine and wait for at least five minutes. If that does not reset the system, it can sometimes still be corrected by a scan tool, with body control reset capability.
Please see our Detailed Topic Heaters and AC Systems for more information.

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After replacing the compressor on my air conditioner the system seems to be over charged, not cooling and pressure too high. We added the exact amount called for, how can this be?

Too much oil in the system will displace the refrigerant and cause an overcharge even with the proper amount of refrigerant. This sometimes occurs when oil is added with the new compressor and the system already has the proper amount.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge.
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An air conditioner hose has started to leak at a crimped fitting. Can these connections be repaired?

Crimped fittings do not just become loose, the rubber in the hose is likely deteriorating. This can be a symptom of a contaminated system, and should be fully diagnosed and repaired before additional damage occurs.
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An overcharged air conditioner has what symptoms?

The leading symptom will be inefficient cooling, though the system may continue to cool. The result will always be elevated head pressure and normally very rapid damage to the compressor.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge.
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Can a worn serpentine belt cause my air conditioner to stop working at times?

Yes, a worn belt can slip slightly and generate heat. There may be no noise or other outward symptom of slipping. The heat generated by the slipping belt over-heats the air conditioner clutch and can cause it to release. This heat may also permanently damage the clutch. Serpentine belts should be inspected with a gauge made for the purpose and not simply visually inspected.
For more information on belt inspection, please see our Detailed Topic, Symptoms of A Bad Serpentine Belt and EPDM Belts.

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Could a dirty cabin filter cause the evaporator to freeze up on my vehicle air conditioner?

Lack of air flow caused by a restricted cabin filter can cause the evaporator to freeze as well as other problems. Lack of air flow can also contribute to refrigerant not fully evaporating to gaseous form. If refrigerant leaves the evaporator in the liquid state, it can cause compressor damage.
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How could a bad catalytic converter cause my air conditioner to stop cooling?

A plugged catalytic converter could cause the engine to overheat and the air conditioner may be shut off as a result. Another way might be if the bad converter reduced idle speed. Many vehicles shut off the air conditioner if idle speed falls below specifications.
For more information on catalytic converters, please see our Detailed Topic, Catalytic Converters Problems.

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How could an air conditioner get over charged?

The leading cause is improper service; Trying to charge the system by watching gauges, rather than evacuating and adding a measured content. As little as two ounce can cause a major problem on some systems.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge.
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How does an automobile air conditioner clutch work?

Most air conditioner clutches have three primary components. The hub, drive-plate and magnetic coil. The hub mounts to the compressor with a bearing. Being mounted on a bearing allows the hub to turn freely, driven by a belt. Inside of the hub is the magnetic coil. When air conditioning is desired an electrical current energizes the coil. This pulls the drive-plate firmly against the hub. The drive-plate is anchored to the compressor shaft so once the coil is energized, the drive-plate and compressor shaft are turned by the hub and belt.

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How does an expansion valve work in an air conditioning system?

Air conditioning functions by converting a high pressure, liquid refrigerant to a low pressure gas. This is accomplished by restricting the flow of the high pressure liquid. As flow is restricted, pressure drops, the liquid flashes to a gas and absorbs heat [energy] in the process.

An expansion valve is a temperature/pressure controlled device to accomplish the pressure drop. As the temperature and pressure approach freezing, the expansion valve can close and limit the refrigerant flow. This has the advantage of keeping the evaporator as cold as possible while preventing freezing. If the evaporator core were allowed to freeze, cooling would be diminished. The expansion valve maximizes cooling by keep the evaporator core at the optimal temperature.

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How does and air conditioner produce cold air?

Air conditioning works by removing heat. Since the absence of heat is cold, this is what we experience. The process works because when matter changes state (e.g., liquid to gas, solid to liquid) energy is absorbed or released.

The refrigerant in the system enters the compressor as a low pressure gas. The compressor raises the pressure and makes it a high pressure gas. This high pressure gas is forced through a condenser, where it changes state to a high pressure liquid. In changing state, energy is released. This is the heat we feel being blown away by the fan, outside of the vehicle.

The liquid now travels to a restriction, built into the system. Flowing through the restriction the pressure is greatly lowered. As the pressure drops, the liquid changes state to a gas. This change of state absorbs energy in the form of heat from the vehicle interior. Removing this heat results in cooling the vehicle. The low pressure gas now returns to the compressor and the cycle begins again.
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How does drawing a vacuum on an air conditioner help remove moisture from the system?

Water boils at 212 degrees Fahrenheit, in the atmosphere and at sea level. As pressure drops, so does the boil point. Reducing pressure to 29 inches of vacuum, causes water to boil at 76.6 degrees Fahrenheit. As the moisture in the air conditioner boils it turns to vapor, which is drawn out with the vacuum pump.
For more information, please see our Detailed Topic How Automotive Air Conditioning Works.

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How long does water normally drip from the air conditioner in a vehicle once turned off?

Water dripping under a vehicle is from condensation of the humidity removed and should stop in less than a minute of shutting the vehicle off. Continued dripping is often a sign of an evaporator that is freezing, a leaking heater core or a restriction in the drain.
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I have a Jeep Cherokee with a very musty odor that comes from the air conditioner vents. Is there anything that can be done?

Depending on the severity of the problem there are several approaches. First with the vehicle doors open and the air conditioner on high, place the dash selector to the fresh air setting. Select a disinfectant in a spray and spray the mist into the fresh air intake at the base of the windshield. While continuing to spray have some one turn the vehicle off and let it sit for several hours. In minor cases this gives good results.

In other cases it may be necessary to remove the blower resistor and/or fan motor and spray the evaporator core with a professional strength product. This is best done by a professional as these chemicals can be highly toxic.

In more severe cases removal of the dash, evaporator core and replacement of the insulating film around it are necessary. This also involves complete cleaning and disinfecting of the core and all duct work. Recharging of the air conditioning system would also be needed so this usually falls into the realm of professional service.
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I have a strange problem. At idle my air conditioner cools okay. If I speed up the engine or start driving, the temperature warms up. Any ideas?

Reduced cooling at higher engine speed often means there is a restriction in the system. If there are no kinked or smashed hoses or lines, there will normally be a plugged component. Common problem areas are the orifice tube, if so equipped or the expansion valve if not. Plugging of components is normally a symptom and points to a larger issue, the source of the material that caused the blockage. Very often this is going to indicate a failing compressor or a ruptured descant in the accumulator.
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I have been told it is not proper to simply add refrigerant to an A/C system that is low?

This is correct, it is harmful simply to add refrigerant. There is no way to judge whether the proper charge is in the system, other than to evacuate, and add the proper charge with a charging cylinder. Gauges are far too unreliable and may result in dangerous over or under charging.

With smaller systems, charge quantity is more critical. Most systems hold 32 ounces or less, some as little as 12 ounces. One ounce, on such a small system, results in a 10% error and damage to the system. Overcharge can damage the compressor, coils and ruin seals. Under-charge may not transport oil, resulting in a burned up system.

There is no way to determine air content, nor the amount of oil in the system without evacuation. Small leaks can cause the system to lose oil. Adding refrigerant, without replacing the exact amount of oil we lose, can damage the system. The only way properly to charge the system is completely removing the contents and replace the specified amounts of refrigerant and oil.

See our Detailed Topic article Preventing Air Conditioner Failure for far more details.
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I have estimates to replace a leaking hose on my air conditioning system. One is higher than the others, and includes a receiver/dryer assembly that the less expensive quotes don’t. Should the receiver/dryer be replaced?

The receiver/dryer should be replaced any time the system is opened. It contains a desiccant that removes moisture from the system and is the number one line of defense for the system. This looks like another example of more is less. Doing the job properly the first time is the least expensive route.
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I recently bought a vehicle and notice when sitting at an idle the air conditioning does not cool well.

Lack of cooling at low speed is a common symptom of several problems. When the engine slows (at idle) the AC compressor also slows. This lowers pressures in the system and makes almost any problem more noticeable. An additional factor is AC systems do not produce cold, they remove heat. This heat is given off at the condenser. Sitting still there is far less air moment to dissipate this heat.

A weak compressor, a leak in the system, an over-charged system, a radiator cooling fan not working and several other things will all have this same symptom. The only way to know would be to run a diagnostic check of the system. I would advise doing this ASAP as far more damage normally results, quickly.

See our Detailed Topic article Preventing Air Conditioner Failure for far more details.
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I replaced the AC compressor on my vehicle, how much oil should I add to the system?

Adding oil to an AC system is a bit tricky. Oil circulates with the refrigerant and settles in different components at different times. It is difficult to know exactly how much oil is already in the system and exactly where it is located. The safest bet, if the system has not been previously serviced, is to drain the removed component, measure what comes out and add that amount. If oil has been removed or added previously, draining every component and adding the specified amount may be the only answer. Too much oil takes the place of refrigerant and will result in an overcharge of the system when the proper amount of refrigerant is added.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge.
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If my cabin filter was plugged what would the symptoms be?

Symptoms of a plugged cabin filter will vary based on the design of the vehicle. In some cases there may be almost no symptoms at all. This is because some systems allow a plugged filter to be bypassed with unfiltered air. On other vehicles the airflow from the vents may be greatly diminished. In other cases the evaporator core could freeze and quit cooling after driving a distance. The worse issue may be the possibility of refrigerant not flashing completely and being returned as a liquid to the compressor. In some cases the excessive amperage caused by the fan pulling through a restricted filter can burn up connectors and control panels.
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Is an electronic leak detector better than dye for finding air conditioner leaks?

One is not better than the other, they are complementary technologies. Better shops often use combinations of various electronic and ultrasonic leak detectors as well as dye and even bubble test. Each has a place and each is effective at certain type leaks.
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Is it easier on my air conditioner to turn it off of maximum position when it is very hot?

Actually the maximum position may be easier on the unit than the normal position. Many units pull in fresh air in the normal mode. This hot and humid air has to be cooled, which may increase the load in normal mode. In maximum mode, most units recycle the already cooled air, which may lower the load on the system.
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Is there a problem with adding sealer to my vehicle air conditioner?

Sealers can cause all sorts of problems in air conditioner systems. Some sealers and stop leak products function by swelling seals, which virtually destroys the rubber. Others harden when exposed to air. Perhaps worse, refrigerant contaminated with sealer can no longer be recycled. Since it is against Federal law to release refrigerant into the atmosphere. Because of the costs and liability of disposing of contaminated waste, many shops may refuse to work on the system. The vehicle owner will ultimately pay the costs, if the system is repaired.
For more information on contaminated refrigerant, please see our Detailed Topic on the subject.

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My air conditioner blows hot air. I had it checked and the shop says the system is working. How could it blow hot if it is working?

Most modern systems are re-heat style. This means the air is first cooled and then heated to adjust the temperature. Diagnosis requires an understanding of the entire system as opposed to simply checking the air conditioning. The benefit is dehumidifying the air and infinite temperature control.

The disadvantage is the complexity required. There are a series of ducts and doors, normally controlled by servo motors. These in turn are controlled by the control panel. A malfunction in the system may result in air being heated more than desired even though the air conditioner itself is functioning as designed.

See our Detailed Topic Heaters and AC Systems for more information.
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My air conditioner compressor has become noisy, but the system still cools okay. One mechanic says waiting until it breaks and another suggest changing it now. What is your opinion?

If the compressor fails and comes apart, debris will be spread throughout the system. This is nearly impossible to clean perfectly. Any debris that remains can drastically shorten the life of the new compressor. The system will have to be repaired when it fails. The chances of a lasting repair are much better before complete failure. The cost may also be less now, because the need for extensive disassembly and cleaning would be less likely.
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My air conditioner does not blow as hard as before?

If air volume is lower than normal on all fan settings, suspect a restriction in the system. If the vehicle is equipped with a “cabin” or HVAC filter, check and replace if needed.

Another common restriction is small plastic shopping bags that are drawn into the system from outside. Driving in parking lots, these bags are often pulled into the air intake, blocking the air flow.

The evaporator core can also become restricted. This is common on vehicles without “cabin” air filters. A professional cleaning may be necessary if this is the case. Evaporators are very easily damaged and normally quite expensive to replace.

A malfunctioning mode or blend door, in the duct work can also cause lack of air flow. These doors open and close to duct air through the system. They are operated by servo motors and sometimes vacuum controls. When they malfunction air flow may be blocked.

See our Detailed Topic Heaters and AC Systems for more information.
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My air conditioner drips water under my car. Where does the water come from?

Air conditioning not only removes heat, but also removes humidity from the air in the vehicle. Lower humidity makes the temperature much more comfortable. The humidity in the form of water, collects on the evaporator core. As it drips off the core, a tray catches the water and directs it outside the vehicle, where you see it dripping.
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My air conditioner stopped working and the shop refused to work on it. They said the system was contaminated, what can I do?

Adding chemicals to an air conditioner, such as sealer and some off-brand refrigerants may contaminate the system. Federal law states that refrigerant should be recycled. Shops use an electronic identifier to test content before recycling. Recycling is usually impossible with a contaminated refrigerant. The contents will have to be removed, with a machine dedicated for the purpose. The waste may then have to be identified by a lab, before a processor with accept it. Normally waste is transported to a facility and destroyed. The considerable cost is charged back to the vehicle owner. A contaminated air conditioner may be considered not practical to repair, due to the expense of removing and destroying the contaminants.
For more information on contaminated refrigerant, please see our Detailed Topic on the subject.

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My air conditioner stops cooling after driving for a while

Two of the leading causes for lack of cooling, after driving for a distance, are the system freezing up and the compressor clutch overheating. Several things can cause either. Lack of air flow, such as a restricted cabin filter can cause the evaporator to freeze. Low charge, a sticking expansion valve and moisture in the system, are other possible causes.

The compressor clutch may overheat and not engage. This will keep the compressor from turning and stop cooling. The drive-plate (see How does an automobile air conditioner clutch work) can wear, increasing the gap between itself and the hub. When this happens it will slip. The slippage creates heat and the coil will release. Once the clutch cools, it may begin working again.

Normally with freeze up, there will be a lot of water dripping under the vehicle, after the unit is turned off. With a bad clutch, there will be little or no dripping.
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My air conditioner will blow fine on high but no air comes out at any other speed. Any ideas?

Most air conditioner blower speeds are controlled by a module or a resistor unit. On high speed, the system often bypasses this component and runs full voltage to the blower motor. If the module or resistor unit fails, the fan will not blow on any speed except high. Failure of these units is also often accompanied by burned connections in the wiring. The root cause is excessive amperage being drawn by the blower motor. The amount of amperage being drawn should be checked before replacing the module or resistor unit.
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My older vehicle needs air conditioner repair. With the price of R12 should I consider converting to R134A to save expense?

At AGCO we do not convert air conditioning systems from one refrigerant to the other. Rather we repair R12 systems with R12. The condenser and hoses on an R12 system are different than those on a system designed for 134A.

Even with the price of R12, the refrigerant in a system is only a small part of the cost of repair. In a very large system the cost difference is usually less than $120.00. In most systems it is considerably less. This small savings can be quickly eroded by an air conditioner that does not cool as well as before. Worse is a system that loses refrigerant or has to be redone.
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My vehicle air conditioner stops cooling when I sit at an idle but cools driving down the road.

Some of the more common causes include, a weak or non-functioning A/C condenser fan. Without a fan to move air through the condenser, pressure will rise and the compressor may be shut off. Driving provides air flow without the need for the fan.

Another cause is a weak compressor. A weak compressor may produce adequate pressure while the engine is running at speed but not enough at an idle. A vehicle low on charge can also show similar symptoms. Finally, an engine idling too low may cause the compressor to shut off. A dirty throttle body sometimes causes this condition.
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My vehicle blows cool on the right side and warm on the left.

In systems with dual zone temperature control, this can indicate a failed blend door or servo. Other causes can include a bad automatic temperature control head and being low on refrigerant. Since the evaporator core is almost always on the right, a low system can sometimes cool the right and not the left.

For much more information, please also see our category on air conditioner service.
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Occasionally, when my AC is on and I accelerate, there is a loud squeal that occurs. This never happens with the AC off.
A bad or loose belt is a possible cause. Check the belt and the tension device. If they are good, liquid returning to the compressor can cause such a noise. Liquid cannot be compressed and the compressor temporarily locks up, causing the belt/clutch to squeal loudly. Tremendous damage can be done to the system. A few possible reasons for this problem include.
- The system is over charged, too much refrigerant has been added.
- Too much oil has been added to the system
- Insufficient air flow across the evaporator. This can result from a dirty cabin filter, dirt in the evaporator, a bad blower motor, a restricted air duct, etc.
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Recently a shop suggested that I have my air conditioner dryer replaced, evacuated and recharged as a preventive maintenance. Can this extend the life of the unit?

This procedure is not in any manufacturer’s recommendations that I am aware of. With their current trend toward reducing maintenance it is not likely to appear in the future. But then, they have a vested interest in vehicles not lasting too long.

That being said, I cannot see any harm as long as the job is properly performed. One problem might be in a cost/benefit analysis. A good deal of research would need to be done to justify the cost and I am aware of no such research. With no prior knowledge you would be guided by theory alone, but the potential for savings is possible.
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Should I turn off my air conditioner when starting my vehicle to lessen the load on my battery?

Modern vehicles control the air conditioner through the body control module (BCM). It is not necessary to turn the unit off when starting as the BCM will do this automatically.
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The air conditioner blower (fan motor) on my Honda is noisy on high. Will it hurt anything to not change it immediately?

Noise is one indication of a failing or restricted motor. A good fan motor normally draws around eight to ten AMPS. Much more is a problem and will burn out the transistor that controls the speeds and possibly damage the wiring harness. With a bad or restricted motor, this may occur. Replacement should be as soon as possible.

We also find cases of leaves and debris that get into the blower and make noise. This is an easy problem to correct. You might pull the motor and see if there is any debris in the fan. If not I would replace the motor, as soon as possible.
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The air conditioner clutch has gone out on my vehicle. The mechanic wants to change the compressor and clutch, is this best?

The clutch and compressor have gone through the exact same number of cycles. If the clutch has failed the compressor will likely not be far behind. A quality clutch assembly cost nearly as much as a new compressor with a clutch and the time to replace is nearly equal. I agree with your mechanic, I would suggest replacing both.
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The air conditioner in my Toyota does not cool as well as it used to. I have been told it is not proper to just top it off like I used to do. Can you explain why this is no longer acceptable?

The practice of “just adding a little Freon,” was never a proper procedure. With R134A refrigerant the results can be catastrophic. Systems are much smaller than they used to be and the volume of charge is much more critical.

Reading the pressure, as with an older system is not accurate with the very small system of today. A slight under-charge can result in the compressor not being lubricated and a slight over-charge can damage the system, from excess pressure. The best way to service the system is to evacuate fully. Then the exact amount specified can be added with a charging cylinder.

See our Detailed Topic article Preventing Air Conditioner Failure for far more details.
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The blower control module in my vehicle has been replaced twice. Why would it keep failing?

Blower control modules are often ruined because the blower motor pulls too much amperage through them. Tell-tale signs are connectors that are melted, discolored and burned wires. The blower motor should be checked for excessive current draw. A restricted blower air intake, for instance from a clogged cabin filter, can also cause the motor to draw excessive amperage.
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The clutch on my air conditioner is making noise. Can it be replaced separately or must I replace the entire compressor?

The answer depends on the vehicle and how many miles it has. On some vehicles, a new compressor with a clutch is not much more than the cost of the clutch alone. If the vehicle has high-mileage it may be as wise to replace the entire compressor, which may fail in the future.

The best course is to ask for an estimate both ways and decide based on the price difference and how long you plan to keep your vehicle. At AGCO we normally present an estimate both ways with a recommendation based on experience with the vehicle.
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The compressor on my air conditioner is bad and I have received widely ranging price quotes, what should this job cost?

It would be impossible to quote a price without knowing the problems in the system. Price could vary greatly for many reasons. The most important thing to remember is why did the compressor fail.

If you have read our philosophy on lowest price verses lowest cost, you will know we believe that a high quality repair is much less expensive than a cheaper temporary repair.

For example compressor failure can be due to high system pressure. This can be due to cooling fans not working properly. Failure to diagnose the cooling fans may result in a lower estimate of repair, but can also result in the compressor failing again.

Other price differences could be due to a rebuilt compressor being used rather than a new one. Rebuilt compressors rarely give equal service to new. Other factors include flushing the system of contaminants, replacing the filter/dryer and sometimes the condenser.

All these factors and others, will drastically affect price. They also drastically affect performance and life of the system.

I feel it is always less expensive to diagnose properly and repair the system fully, even though the initial price may be more expensive.
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The compressor on my vehicle locked up. The shop that checked it said I should replace the condenser as well as the dryer, expansion valve and compressor. Why should the condenser be replaced if it is not leaking?

The condenser on a R134A system has many, many feet of tubing, with very small passages. When a compressor seizes up, there is normally a great deal of metal particles that enter the system. These particles are often lodged in the tiny condenser passages. There is no way effectively to clean such a condenser. Should a particle become dislodged later and go through the new compressor, damage will occur. With a metal contaminated system, condenser replacement is a wise step.

The image below shows an actual section of condenser tubing and how small the tube openings are. In a serpentine design condenser, these tubes wind back and forth and are very long.

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The heater in my vehicle blows only cool air regardless of the dial setting.

If the vehicle has a temperature gauge make sure the engine is getting to operating temperature. If there is no gauge, temperature can be checked with a thermometer. If the engine is warm enough, normally 195 degrees Fahrenheit or more, flow should be checked. By checking the inlet and outlet temperature on the heater hoses, it can be determined if the hot water is flowing through the heater core.

If flow is present and adequate, there is likely a problem with the blend door in the heater case. The blend door ducts air through the core when heat is desired and around it when not. If the door does not operate, heat will not enter the passenger compartment.

Blend doors are controlled by a number of means. Some are cable or vacuum operated, others electrical and many are computer controlled. Diagnosis of computer controlled heating, ventilation and air conditioning (HVAC) systems is quite complex and best left to a properly trained professional.

If your system is vacuum operated, check to see if the vacuum lines are attached and that there is a source of vacuum to the system. On a cable system turning the knob should move the cable, which should be attached to the door.

See our Detailed Topic Heaters and AC Systems for more information.
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The high-side pressure on my air conditioner is too high and the system does not cool well. What things could cause this?

Excess high-side pressure can result from insufficient air flow pass the condenser, restrictions in the lines or an overcharged system. Bad cooling fans and/or clutches as well as control circuits are common faults. Check to see if the fan(s) are running at full speed or as commanded. Another cause is a dirty condenser core. Debris, leaves and dirt may restrict air flow.

The only way correctly to verify the proper refrigerant charge, is to evacuate the system and add the proper amount. System over-charge will diminish cooling and can quickly destroy the compressor and damage the system.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge.
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There is a leak in my air conditioner that I cannot find. About once a year it quits working and must be charged. Dye was added to the system but does not show up.

Systems today are very small in comparison to just a few years ago. Some systems only hold 16 to 20 ounces. This makes leaks far more critical. Losing just two ounces can shut the system down and a two ounce a year leak can be hard to find. If dye does not show on any of the external components, the evaporator core is a prime suspect. We use a remote camera system to inspect the evaporator and have found several leaks by this method. Placing the wand of an electronic leak detector in the evaporator case may also help reveal such a leak.
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There is a slow leak in my air conditioner and have been told sealer can be added to repair this. Is this a good idea?

Definitely not a good idea. Sealer normally functions in one of two ways, either it swells seals or it hardens when exposed to air or moisture. The theory is the swollen seal will seal better and the leak is plugged by the hardened material as it leaks out.

Any sealing from these concoctions will likely be temporary and they can do great harm. If they harden in your system they can be almost impossible to remove. This can cause any attempt at proper repair to fail. Hoses and internal rubber components could also be damaged. Many shops will refuse future repair or insist that every part of the system be replaced.

A professional will locate and repair the leak properly. This will be much less expensive in the long run and is the only repair that should be considered.
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Three compressors were replaced on my vehicle in the last three years. They work okay for a while and then start to leak at the seal between the halves of the case. Are these all defective are is something causing this?

It is very unlikely that you would get three compressors with the same problem. Many times, leaks like you describe, are caused by system pressure rising too high and distorting the case of the compressor. This can result from over charging or cooling fans that do not operate properly.

High side pressure is closely related to temperature. If the condenser gets too hot, the pressure will rise. The fans are designed to help control this and their function should be verified.

Charging a system improperly can result in the same problem. Charging a system by checking the pressure is not accurate. Pressure varies considerably with ambient temperature. A system charged with such a method, on a cool day, may be vastly overcharged on a hot day.

Too much oil in the system could also cause an overcharge. The system needs to be completely drained and all oil removed. Refill with the specified amount of oil, evacuate the system and the proper amount of refrigerant should be added.
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What are the benefits of vacuuming an air conditioning system before charging?

Drawing a vacuum on an air conditioning system draws air, that would otherwise be trapped, out of the system. Air occupies space and does not provide cooling. Air also contains moisture which is detrimental to the system. By drawing a vacuum on the system, much of the air and moisture are removed.
For more information, please see our Detailed Topic How Automotive Air Conditioning Works.

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What are the common causes of a serpentine belt burning on the drive pulley?

Serpentine belts getting hot, burning and breaking are sometimes the result of a seized pulley or accessory being driven by the belt. For instance an air conditioner compressor clutch bearing may seize and the belt will start to slip. Slipping generates tremendous heat and will quickly burn the belt. Worn belts may also slip and overheat the accessory items.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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What are the symptoms of a bad air conditioner clutch?

An air conditioner clutch is actually several parts (see How does an automobile air conditioner clutch work.) The symptoms will depend on the part that fails. When the bearing fails, the first symptom is noise, eventually resulting in the hub seizing. When the hub seizes, the belt will slip, squeal loudly and break.

A failed magnetic coil will keep the compressor from operating. The first symptom will be a lack of cooling. Coils also fail intermittently. Intermittent failure results in lack of cooling, normally after driving a distance. Other symptoms can include noise and a burning smell.
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What are the symptoms of a bad evaporator core?

The primary failure on evaporators is a leak, the symptom would be a loss of refrigerant and a loss of cooling. Evaporators may also become restricted externally as well as internally. With an external restriction, reduction of air volume from the vents would be a symptom. With an internal restriction, loss of cooling after driving is the normal complaint.
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What are the symptoms of a dirty evaporator core?

Dirty is a relative term and so are the symptoms of a dirty evaporator. A small amount of dirt might diminish cooling slightly and/or restrict air flow from the vents. A more severe amount of debris can significantly block air flow. Blocking air flow can result in the evaporator freezing. A frozen evaporator will quit cooling and may inhibit liquid refrigerant from turning to a gas. If refrigerant does not fully convert from liquid to gas, returning liquid will damage the air conditioner compressor.
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What are the symptoms of a plugged cabin filter?

A decrease in the volume of air coming from the vents is one sign. Another is a noisy blower, one that sounds like it is turning faster than it is. Restricted cabin air filters can also cause blower motors to burn up, by increasing the amperage they draw. In extreme cases temperature control computers can also be damaged by the higher amperage.
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What are the symptoms of an over charged AC system?

Lack of cooling and short compressor life are the leading signs. Excessive compressor noise may or may not also be a symptom.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge.
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What are the warning signs of an air conditioner compressor failing?

The two most common symptoms are noise and lack of cooling at idle. When a compressor becomes noisy, failure is imminent. Replacing it before it fails completely can often prevent a great deal of complications. Lack of cooling at idle can also have other causes. A pressure test of the system is the best way to isolate the exact cause.

Compressors normally fail for reasons other than the compressor itself. Careful diagnosis is needed to prevent recurrence of the problem. See our Detailed Topic article Preventing Air Conditioner Failure for far more details.
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What can I do to extend the life of my vehicle’s air conditioning system?

Keeping the condenser clean is always a very good idea. Carefully washing dirt and bugs from the condenser can lower the load on the system considerably. Replacing the “cabin” filter if the vehicle is so equipped can also help considerably. Most of these filters need to be replaced about every 15,000 miles.

Keeping a good drive belt on the compressor is also critical. Old and worn belts can slip and generate tremendous heat which can damage an air conditioner clutch. Also the system should be serviced immediately when a problem is noticed. For instance insufficient cooling can indicate a low charge, which indicates leakage. Continuing to drive with a low charge may shorten the life of the system.

Lastly a system should never be “topped off.” This is where refrigerant is added to a partially filled system. Rather any leak should be addressed if possible, the system fully evacuated and recharged with the proper amount of refrigerant.

See our Detailed Topic article Preventing Air Conditioner Failure for far more details.
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What is a cabin filter?

The cabin filter is very similar to the filter on a home heating and air conditioning system. It filters air flowing to the evaporator and heater core. By removing dust and debris from the air flowing through these cores, the problem of plugging the air passages are greatly reduced. Not all vehicles have a cabin filter. Those that do need to be replaced on a regular basis.
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What would a greenish liquid leaking from the air conditioner (AC) condenser of my vehicle be?

If the source of the liquid is the AC condenser, it is very likely trace dye that was added to the system. Many manufacturers and service shops add fluorescent dye to air conditioners to aid in leak detection. With a black light and special glasses the area of the leak is very visible. Amounts large enough to be seen with the eye represent a significant leak in the system. Immediate repair of the leak will help control cost, future damage and contamination of the system.
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When adjusting the inside temperature of my car, there is a popping noise under the dash.

Temperature on modern vehicles are controlled by a series of electrical actuators and doors that they open and close. Most popping noise under the dash relates to these systems. Often the plastic doors will crack at the point where the actuator drives them. This causes the drive to slip and produces a pop or click. Damaged actuators can also make a pop or click noise.

See our Detailed Topic Heaters and AC Systems for more information.
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When driving, my air conditioner cools fine. When I sit idling the vehicle warms up.

There are several possibilities. One is a weak compressor. A weak compressor may produce enough output when turned at higher RPM but not at idle. To test, place the vehicle in neutral and slightly raise the RPM with the accelerator. If cooling returns this is a possibility.

If cooling does not appreciably increase, there could be a problem with the cooling fan(s). In order for the air conditioner to function, it must give off heat at the condenser. Driving at speed produces enough air flow. When sitting at idle fans must move this air. If a fan fails to turn or turns too slowly the air conditioner may not cool or shut down.

Being low on refrigerant can also cause this problem. This could be tested by evacuating the system and measuring the charge. If the system is low, it indicates a leak, which should be repaired. Another frequent symptom of low charge is a compressor that cycles on and off frequently.
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When my air conditioner gets too cold I sometimes turn the heater on slightly. A friend said this could damage my air conditioner.

Many vehicles blend heated air with air conditioned air to control passenger compartment temperature. This will not harm the air conditioner.

See our Detailed Topic Heaters and AC Systems for more information.
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When my vehicle sits at a stop light or is not moving the air conditioner quits cooling. When diving 45 MPH it cools fine.

This will almost always be one of three problems. If idle is too low, the computer can turn the compressor off. This can be checked by watching the RPM on the vehicle tachometer. Other causes may be the condenser fan is not working fully, or the compressor is weak. When driving 45 MPH the condenser fan is not required, due to natural air flow. If the fan does not work or work at full speed, the vehicle will warm-up when sitting still.

A weak compressor acts similarly. The compressor will not produce enough pressure differential, at idle. At higher vehicle speed, the RPM increases and the AC may cool. To test for this, try elevating the RPM at idle. Put the vehicle in neutral and accelerate and hold at 2000 RPM, if cooling gets much better, the compressor is likely.
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When starting my vehicle, should I switch off my air conditioner, to reduce the strain on the starter?

Virtually all modern vehicles control the air conditioner compressor through the power or body control module. Switching it off during cranking is unnecessary as the computer does this automatically.
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Why do air condition systems today seem to leak more than in the past?

Actually systems today leak less than past units. Hoses and connections are much better today. Systems also hold far less refrigerant. Older systems often held up to 60 ounces of refrigerant. Systems today may hold as little as twelve ounces. A three ounce leak in a 60 ounce system was hardly noticeable. In a twelve ounce system, three ounces represents 25% of the capacity and the system will stop cooling. The effect of losing refrigerant is simply far more critical today.
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Why do automobile air conditioners fail?

By a wide margin, the two leading causes are leaks and improper service caused by mis-diagnosis. When a leak develops, refrigerant as well as system oil can be lost. This can cause a wide range of other problems, including compressor damage.

There are several reasons why an air conditioner may stop cooling. Adding refrigerant to a system, rather than diagnosing the problem, results in over charging the system. This will quickly damage other component and not correct the original issue.

Please see our Detailed Topic entitled wasting thousands on AC repair for more information on system over charge
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Why does my air conditioner cause water to drip under my car?

Air conditioning makes the passenger compartment comfortable by removing heat and humidity. The humidity that is removed from the air is seen as water that drips under the vehicle.
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Why does my engine bog down when I turn on my defrost?

Engine speed is controlled by a component called an idle air control or IAC servo. When the defrost is selected, the air conditioner is turned on. The dehumidified air helps to defrost the windows. The load change from the air conditioner causes the engine to slow down. When operating properly, the idle air control or IAC servo will correct the idle speed, almost immediately. When the IAC sticks or works slowly, there may be a noticeable change in speed when engine load changes.
For more information, please see our Detailed Topic Idle control and electronic throttle control.

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Why would an orifice tube keep clogging up on an air conditioning system?
Unless sealer has been added to the system, three things often cause contamination in an air-conditioning system.
1. Metal, usually from a bad compressor.
2. Burned oil, also from a bad compressor.
3. A ruptured receiver/dryer
If a sealer has been added to the system, the refrigerant may no longer be able to be recycled. The expense of removal and disposal may be excessive. Contaminated systems are always extremely difficult to correct. Sometimes, replacement of every component is the only remedy, and this is on top of the costs of waste disposal.
For more information on contaminated refrigerant, please see our Detailed Topic on the subject.
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Why would the air conditioner on my vehicle stop blowing out of the vents and start blowing defrost when I accelerate my vehicle?

Many times the mode door, that controls blower position is vacuum operated. When you accelerate, engine vacuum drops and spring pressure returns the mode door to the default, which is defrost. There is a vacuum accumulator that stores vacuum to prevent this. Chances are the line between the vacuum source and the mode door actuator is leaking. The most common places for leaks are at the engine firewall and under the battery.
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Why would the blower motor resistor keep failing on my vehicle?

Resistor failure is almost always the result of excessive amperage being drawn through it. The leading source of excess amperage would be a bad blower motor or a motor that is restricted. Poor or loose wiring connections can also increase amperage in a circuit. An ammeter can test motor-draw and a voltage-drop or resistance test can check bad connections.
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Why would the clutch on my air conditioner fail?

An air conditioner clutch is mechanical and electrical and is prone to wear and tear. They normally last 100,000 miles or more, under normal conditions. Low charge in the system, caused by a leak, may produce over-cycling and quickly wear the clutch. Over-charge, from improper service can also destroy the clutch and compressor very quickly. A dirty condenser will cause excess pressure as will an inoperative condenser fan. Worn drive belts may also drastically shorten compressor clutch life.
For more information on belt inspection, please see our Detailed Topic, Symptoms of A Bad Serpentine Belt and EPDM Belts.

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Alignment, Frame, Wheels & Tires

A friend told me that aircraft use nitrogen to fill their tires. Should I consider it for my vehicle?

The Federal Aviation Administration (FAA) specifies nitrogen fill in aircraft tires. This is largely a fire concern. Nitrogen does not support combustion as well as air. In the event of a brake or wheel fire, it is hoped this could be a positive factor. The advantage on an automobile is generally not worth the cost or inconvenience.

For more information, please see our Detailed Topic Filling Tires With Nitrogen.
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A friend told me there is a specific procedure for tightening lug nuts, is this correct?

There is a specific torque, for each vehicle and a recommended tightening pattern. I like to torque lug nuts in three stages. For instance if the specified torque is 90 foot pounds, I would complete the pattern at 30 foot pounds and then repeat at 60 foot pounds and finally finish with 90 foot pounds. The tightening pattern normally involves moving to the lug furthest from the last lug tightened. Torque varies greatly from one vehicle to another and service information should be consulted for the proper amount.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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A nail punctured one of my tires and my tire warning light came on. I put tire sealant in the tire and inflated it. The light went off, but now it is back on and filling the tire does not make it go off.

A vehicle with an in tire pressure monitoring system (TPMS) has a sensor in the tire that reads air pressure. Tire sealant can enter the sensor and quickly cause damage. A proper repair will involve dismounting the tire, repairing the puncture, thoroughly cleaning the interior and replacing the TPMS sensor.

For more information, please see our Detailed Topic Valve caps and TPMS.
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A tire store broke three of my lug studs, trying to rotate my tires. They say the last person who installed the wheels caused the damage. Who do you think is right?

Most times, broken lug studs are caused by improper installation. If the studs broke while the lugs were being removed, chances are it was previous damage. If the studs were broken while installing the wheels, I would suspect too much torque being used or the nuts improperly started on the studs.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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A tire store recently told me I needed new tie rod ends. They squeezed the tie rod with a large pair of pliers and showed me the movement. Should I let them replace the tie rods or take it to an alignment specialty shop?

Squeezing tie rods with a pair of pliers is improper and will often damage good tie rods. Best is to take the vehicle to another shop and have it properly inspected.
For more information, please see our Detailed Topic, Properly Checking Tie Rod Ends.

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After being in an accident, my car does not drive the same as before. All of the body panels fit well and the wheel alignment is set. Could it still have a bent frame?

The term frame is often used interchangeable with unibody, though they are technically different. The precision required in unibody repair is normally greater than required with a frame. It is quite possible there is still damage that was not addressed. Body repair shops are very good at cosmetic work, because that is the bulk of what they do. Intricate frame and suspension problems often require a specialist to locate and correct.

See our Detailed Topic Frame Repair, The Good, The Bad and The Ugly for more information on hidden chassis damage.
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After buying new tires my car has a vibration or shimmy in the steering. I had the balance checked and it is okay.

Balance is one component of vibration. A tire that is not round will also vibrate, even though it is balanced. For instance a square block could be balanced, but would not roll smoothly. A well equipped shop should have an indicator for measuring tire run-out. The device rolls or slides on the tire tread, as the tire is rotated and indicates the amount the tire is out of round. No run-out is preferred, but anything over 1/16" inch will normally cause a noticeable vibration.

See our Detailed Topic article Ruining New Tires for far more details.
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After having my tires rotated, the rear of my expedition sinks down over night. Do you think this problem is related to the tire rotation?

Suspension air bags are made of rubber and have a life. They should be inspected annually after six years and replaced as soon as they show cracking. Chances are the bags will be dry rot cracked. When the vehicle was raised for the rotation, the bags extended further than normal. This may have revealed the problem, but really did not cause it. An inspection of the system should tell for certain.

For more information please see our Detailed Topic Ford Air Suspension Problems.
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After having the rack and pinion replaced, the steering wheel in my vehicle is not centered when I drive straight. How do I center the steering wheel?

Replacing the steering gear should include resetting wheel alignment. Centering the steering wheel is part of any proper wheel alignment. The steering wheel is locked in a centered position while adjusting the right and left tie rods until the distance between the front of the tires and the rear is correct [toe] and the front tires track straight with the rear.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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After replacing the battery in my Saturn ION, I noticed the power steering was hard to turn and there was a warning light on the dash. Where is the power steering reservoir?

Many vehicles today use electric power steering and have no steering reservoir. Instead an electric motor and series of sensors provides power assist. These systems are very susceptible to voltage and easily damaged. Check the fuse box to see if the power steering fuse is blown.
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After rotating my tires there is a distinct whine noise when I drive.

If the noise was not present before rotating and started immediately after, a likely cause is the tires. Rear misalignment of the suspension can cause rear tires to wear in spots. This comes on slowly and because the rear of a vehicle is relatively light, the noise is not noticeable. When the tire is moved to the front, the weight of the power-train is being supported. This causes the noise to become far more noticeable.

To confirm this theory, closely examine the tire tread. Run your hand over the tread and see if you feel high and low spots. Next rotate the tires to the original positions. If the noise goes away, this is likely the problem. Replacing the tires is the only cure, but the original cause must be found are it will recur. A quality suspension shop should be able to diagnose the root cause for you.
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Are cracks in a tire sidewall dangerous?

Even very minor cracking should be cause for concern. One cause of cracking is age. Many experts and vehicle makers state six-years is the maximum safe life of a tire. The cracking can be a symptom of even more serious problems. See our Detailed Topic article Old Tires With Good Tread for far more details.

Severe cracking at low age is usually a defect in the tire, a deficiency in manufacturing. This can be very dangerous and the tire should not be used.

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Are there any advantages to the larger diameter wheels and tires on newer vehicles?

The only advantage is appearance and only if the look appeals to you. They are considerably more expensive to replace, give a rougher ride, compared to a taller sidewall and are easier to damage when hitting pot holes. They may also make the vehicle stand out and provide an inviting target to thieves.
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At what mileage should I get a wheel alignment?

Wheel alignment is NOT dependent on mileage. Wheel alignment only needs to be set when there is a problem. Some vehicles may never require alignment. Symptoms of possibly needing wheel alignment include, tire wear, a pull to the right or left when driving and a steering wheel that is not centered, when driving straight. With none of these symptoms it is doubtful a wheel alignment is needed.
For even more information on wheel alignment, please see our Detailed Topics article, Wheel Alignment Myths.

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Buying a new set of tires, I was told my ball joints were bad. I have no symptoms and no tire wear, should I be suspicious?

With no tire wear or other symptoms, I would look for a second opinion or a better explanation. Ball joints can have a significant amount of up and down movement, when unloaded. This in itself is not a reason to condemn the ball joint, unless there is also side to side movement.

Please see our Detailed Topic All About Ball Joints for more information.
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Buying a set of tires, the salesman tried to sell me nitrogen to fill them. Is using nitrogen to fill tires worth the expense?

In automotive and light truck tires nitrogen fill is more of a gimmick than an advantage. Nitrogen molecules are larger than oxygen and for that reason are thought to leak out of tire more slowly. Considering air is about 79% nitrogen already, the difference is almost nil. Buying tires from a business that mounts and balances them properly and uses a quality valve stem will have far more advantages.

For more information, please see our Detailed Topic Filling Tires With Nitrogen.
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Can a bad tie rod cause my car to pull to one side when driving?

A seized tie rod could cause a pull but this is fairly rare. Pulling is not a normal symptom of a worn tie rod. Wear causes slack which effects toe and will wear tires and produce slack in the steering.
For more information, please see our Detailed Topic, Properly Checking Tie Rod Ends.

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Can a bent frame cause a bumping noise when I drive?

The symptoms of a bent frame can vary widely depending on the nature, severity and position of the damage. A bumping noise may sometimes but not always be a symptom. This is often the result of components moved out of position and striking one another as a result. Other symptoms may be, rapid wear of suspension and drive line parts, tire wear, poor driving and vibrations.

See our Detailed Topic article Frame and Unibody Damage for far more details.
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Can a cracked frame be repaired?

Cracks in a frame can be repaired but this requires very specialized welding and metal working techniques. This is a specialty requiring a knowledge of welding, heat affect zones, high-strength-low-alloy (HSLA) metals, stress relieving and more. The metal must be repaired to its original strength but not beyond. Plating and reinforcing the area of the crack can cause stress risers which may create future cracks in other areas. This type repair is best reserved to a frame and unibody specialist.
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Can a new tire be out of round?

New tires that are out of round tires are actually common. Out of round is a defect, normally built into a tire, rather than something that occurs. Improperly mounting a good tire, may cause damage and make the tire out of round.

See our Detailed Topic Out of Round Tires for more information.
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Can a new tire that was just installed be out of balance?

Many new tires are not balanced properly. If either side of the wheel has no weights or multiple weights (more than one on either side) the balance may not be properly done. A change of ride quality, shimmy or vibration, after the installation of new tires is also cause for concern.

See our Detailed Topic article Ruining New Tires for far more details.
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Can a torn tire bead be repaired?

Tire beads are almost always torn by improper mounting of the tire. A torn bead is non-repairable and the tire should be replaced. For more information on proper and improper tire mounting, please see our Detailed Topic article Ruining New Tires.
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Can a vehicle being out of alignment cause a flat tire?

There is no direct correlation between wheel alignment and a flat tire. Lack of wheel alignment can severely wear tires. If a tire were to wear badly enough it could go flat. In this case the flat tire is caused by the wear and the wear was caused by the lack of wheel alignment.

For even more information on wheel alignment, please see our Detailed Topics article, Wheel Alignment Myths.
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Can a vehicle ever be the same after the frame has been bent?

The answer depends on two things, the severity of the damage and the skill of the repairer. Damage to the front or rear sections of the vehicle can normally be repaired to like new condition by a skilled frame shop. Damage to the center of the vehicle is much more difficult to repair properly.

A skilled shop can advise as to the limits of what can be repaired properly. As a general rule, metal that is kinked [bent to a radius of 1/8" or less] may not be repairable. I feel it is a wise idea to have a severely damaged vehicle inspected by a second independent shop, after it has been repaired. This will verify a proper repair or point out problems that should be addressed.
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Can frame damage to a vehicle cause engine damage?

There are two parts to the answer. The things that cause frame damage often also cause damage to the engine, suspension and drive line. For instance, running into another vehicle can easily break mounts off the engine, smash air flow meters and sensors. Running into a ditch can smash an oil pan and break an oil pump.

Driving a vehicle with frame damage can also cause damage. The engine is generally mounted to the frame or unibody. With the mounting out of alignment, far more stress is placed on motor mount, drive axles, the transmission, fuel lines, etc. Damage to these components and more are also common on frame and unibody damaged vehicles. The same is true of many other components. For instance, I have seen many radiators and air conditioner condensers with holes caused by rubbing on nonaligned body panels.

See our Detailed Topic Frame Repair, The Good, The Bad and The Ugly for more information on hidden chassis damage.
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Can I add grease fittings to my suspension which does not have them?

Modern suspension parts are normally sealed and not able to be greased. This has worked very well and they tend to last a very long time. There is no practical way to add a grease fitting, unless provisions are provided in manufacture of the part. This is less common today, as leaving the fitting off cuts cost. It also helps to protect the joint from improper service. Not carefully greasing can allow contamination to enter the joint. Over-greasing can damage the boot, and cause rapid failure.

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Can I lower my car without causing problems?

Changing the design height on a suspension will always create problems. The further from stock height the more involved the problems will be. For a lot more information on modifying vehicle suspensions, see our Detailed topic, Lowering and Raising Vehicle Suspensions.
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Can I substitute a lower rated tire on my vehicle that specifies “V” rated tires. I have been told this is only a speed rating.

The term speed-rating is somewhat misleading. The structural integrity of a tire design is tested by spinning at increasing speed until centrifugal force tears the tire apart. The term “speed rating” arises from the testing method.

Engineers design suspensions to load tires during braking, cornering and driving. If the vehicle is engineered with a “V” rated tire and a lower rated tire is substituted, handling and safety can be affected. Problems may also appear with irregular wear and vibrations. The least expensive tire is the tire designed for the vehicle.
For more information, please see our Detailed Topic, Can I Substitute A Lower Speed Rated Tire.

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Can offset wheels cause damage to my vehicle?

Offset, the relative position of the inside mount surface to the actual center of the wheel, has much to do with how the suspension is loaded. As the center line of the wheel moves farther outward from the inside mount surface of the wheel, the load on the suspension may drastically increase. This extra-load can quickly destroy wheel bearings and suspension support bushings.
Excess offset also increases the scrub radius or the amount the tire drags when the steering is turned. This is due to the pivot point of the suspension remaining fixed while pivot point of the suspension no longer aligns with the center of the wheel. Forward and rearward travel of the wheel when turning is increased often resulting in the tire striking the fender when the wheel is steered.

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Can parking with my wheels turned affect wheel alignment?

Wheel alignment is secured very well, usually by threaded fasteners or cams. Parking with the wheels turned will have no affect on the wheel alignment.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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Can rotating tires cause a vehicle to be go out of alignment?

Rotating tires will not affect vehicle alignment. Tires very often cause driving issues, such as pull, noise and vibration. Moving tires during rotation may cause existing problems to be revealed. For instance a tire with conicity may be hardly noticeable on the rear and cause a pronounced pull when rotated to the front.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.

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Can the air suspension on my Ford be replaced with regular springs?

It can be done, but the results are normally very poor. A great deal of engineering went into the air suspension used on Ford. It is relatively problem free, provides a great ride and good handling. It also allows the suspension to adapt to changes in weight, preventing tire wear. The retro-fit kits that I have seen, are low-quality and greatly diminish the vehicle performance.

I feel a much better plan is to learn to avoid problems with the system. To do this, see our Detailed Topic article Ford Air Suspension Problems.
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Can the strength of a bent frame be preserved when it is straightened?

Proper straightening of metal will not weaken it and a frame is no exception. A frame repaired by a skilled professional will be as strong as the original. This pre-supposes the frame has not previously been damaged by improper repair. Over-heating metal, improperly working metal and repair of metal that is kinked can result in weakening. It is very important to select a true professional for frame repair. Once metal is damaged by improper repair, it can rarely be restored.
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Can two tires have the same DOT number?

Yes, the DOT code is not a unique serial number. Instead it identifies when and where the tire was produced. Many tires of a given size and model produced on a given day may all share the same DOT number.
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Can using nitrogen in tires give better fuel mileage?

No, nitrogen nor any other gas in a tire can influence fuel mileage. The claims by nitrogen-fill proponents compare a tire properly inflated with nitrogen to one under-inflated using air. Their contention is that nitrogen will keep tires inflated better and thus could give better mileage, compared to an under-inflated tire. I think this is misleading at best, as the difference in air retention can be as little as 1.5 PSI per year with nitrogen, compared to air.

For more information, please see our Detailed Topic Filling Tires With Nitrogen.
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Can wheel alignment cause the rear tires to make noise when driving?

Technically, wheel alignment causes wear to the tires. Once worn in spots, the tires can produce a roaring noise very similar to a bad wheel bearing. Distinguishing between the two is easiest if the sound changes on different road surfaces. Inspection of the tires normally reveals uneven wear, in spots. Rotating the tires front to rear may also cause the nature of the noise to change.
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Do wheel weights come in more than one style? The weights on my wheels do not seem to fit well.

Yes wheel balance weights come in a wide variety of styles as well as coated and un-coated. There are gauges that tell which style fits each wheel. Quality shops stock the proper weights for the vehicles they service. Standard weights are natural lead finish and are suitable for steel wheels. Aluminum wheels should use nylon coated weights to prevent corrosion. Coated weights are several times more expensive than un-coated and another sign of a high quality shop.

See our Detailed Topic Wheel Balance, Shimmy and Vibration for more information.
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Does a bent wheel cause tire wear?

A bent wheel can wobble, which can cause scallop wear to the tire. The amount of wear, from the bent wheel is normally not excessive. A more prominent symptom is usually vibration. Many people do see excessive tire wear and a bent wheel. They may then assume the wheel is causing the wear. The tire wear is more likely caused by wheel misalignment, resulting from the same impact that bent the wheel.
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Does a crooked steering wheel necessarily mean bad wheel alignment?

If the steering wheel is crooked, when driving straight, it means the toe adjustment is not correct, side to side. The problem could be either on the front or rear of the vehicle. If this is the case after having the wheel alignment set, it indicates poor workmanship or a lack of diagnostic ability. If a steering wheel that was previously straight, moves to a crooked position, something in the suspension has changed. This is an indication of a problem.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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Does a torn ball joint boot mean the part has to be replaced immediately?

The ball joint boot seals the joint, holds in the lubricant and keeps water and debris out. Once the boot is torn, the joint will fail. The amount of time before the part fails can vary substantially. If the part is not yet worn and giving no symptoms, you can wait, but only if you are willing to regularly inspect the part.

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Does a torn tie rod boot mean I should immediately replace an outer tie rod?

When the boot tears protection is lost and the tie rod will eventually fail. There will normally be no immediate problem until wear and corrosion occur. At that point the tie rod must be replaced.
For more information, please see our Detailed Topic, Properly Checking Tie Rod Ends.

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Does crossing radial tires cause damage? I was told the belts would separate if I crossed my tires from side to side.

Damage from crossing radial tires is a very persistent, false piece of folklore. A particular brand of early design radials did have a separation issue. Crossing was suggested as a possible cause and caught on. Most radial manufacturers today recommend cross-rotation under several circumstances. The only exception is a directional tread pattern. Directional tires will not be damaged but will not flow water out of the tread properly if crossed. This is due to direction of the tire sipes and not the construction of the tire.
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Does my vehicle pulling to one side mean I need an alignment?

Pulling to one side or the other is one symptom of misalignment. There are also many other things that can result in a vehicle pulling, so it does not necessarily mean the alignment is off.

Low air pressure in one or more tires can cause the problem even though the alignment is fine. Another common cause of pulling may be the tire. Even new tires can cause a pull. This is considered a defect in the tire and may be covered by the tire manufacturer’s warranty.

Mismatched tread patterns or tire sizes on opposite sides of the vehicle can also cause the vehicle to pull as can power steering system problems. Most of these symptoms will feel very similar to an alignment problem. If your vehicle pulls to one side when driving, you should inform the shop of the symptom. Allow them to diagnose the problem, rather than requesting an alignment.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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Does parking with wheels in the full lock position cause a vehicle to go out of alignment?

A properly set vehicle wheel alignment is very difficult to affect. Alignment settings are generally locked in place. Parking with the wheels turned, even at full lock will not affect wheel alignment.

For more information, please see our Detailed Topic Wheel Alignment Myths.
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Does the body need to be removed to repair frame damage?

Properly straightening a frame means reversing the damage that has occurred. The body and frame were joined when the damage occurred and should be repaired in the same manner. Removing the body or any structural components before straightening will normally make the process far more difficult. Body components would only be removed after the frame is straightened. Even if a frame is to be replaced, the best shops will normally pull the old frame into shape before separating the body and chassis.
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Does tire sealant ruin TPMS sensors?

Tire sealant can quickly destroy tire pressure monitoring system (TPMS) sensors.

For more information, please see our Detailed Topic Valve caps and TPMS.
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For best ride, what is the minimum air pressure I should use in my tires?

The amount listed on the door placard or in the owner’s manual is the amount required to safely support the weight of the vehicle and should be considered the lowest pressure to be used.
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Getting new tires, I was told of difficulty aligning the vehicle because struts were going out. They told me that it would cost roughly $### and if done with in 6 mo they would not charge for an alignment.

It would be unusual for a vehicle with 66,000 miles to need struts. It is also very unusual to hear a worn strut would offer any difficulty in alignment. The offer to wave the alignment charge also sounds very suspect, in my opinion, you can bet the cost is built in. I would definitely seek a professional opinion from a trustworthy shop.

Original struts are often much higher quality than aftermarket replacements being sold. The originals are designed last at least twice that mileage and normally fail due to poor quality tires, and/or bad strut shaft covers.

What is important to realize is that many things can be called "replacing struts". For instance there are struts that are not as good when new as the originals are with 120,000 miles. You may be removing a better product than you are installing. These cost about 1/10 the cost of the originals and create a substantial profit for the shops that use them.

If the struts are bad, there are also many other factors to consider. The two upper strut mounts, two jounce bumpers and two strut shaft covers, are often not included in such estimates. Omitting these items results in what seems to be a lower estimate, while preserving the profit of the shop.

These items have higher failure rates than the struts themselves and can be replaced for no additional labor when the struts are out. Not replacing these often results in the job having to be done over after a short while and at much greater cost.
For more information, please see our Detailed Topic, How Do You Know When You Need Shocks or Struts

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How can I be sure the unibody or frame on my vehicle was properly repaired after a collision?

A leading indication of frame and unibody problems will be tire wear and handling issues. Having a wheel alignment specialist check the steering angles is very helpful, especially if there are any handling or tire wear issues. There are also independent frame specialist in many cities that can measure the chassis and detect remaining damage.
For more information, please see our Detailed Topic, Spotting Wrecked Vehicles.

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How can I calculate the effect that different size tires will have on my speedometer reading?

The speed indicated is based on revolutions of the drive axle and the circumference of the tire. A taller tire will have a greater circumference and thus travel further each time it rotates. This will have the effect of indicating a speed lower than actually traveled. The easiest way to see the effect is to use the AGCO Tire Size Error Calculator. Enter the original size specified for the vehicle and any other size and the speedometer error will be calculated.
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How can I keep my tire valve stems from dry rotting?

Quality valve stems are built to resist ozone which causes cracking. The Society of Automotive Engineers (SAE) has standards for valve stems (SAE 1205-1206.) Millions of cheap substandard valve stems have been recalled because they do not meet this standard. Valve stems are often replaced when tires are replaced, which should be no less than every six years. If quality stems are used, there should be no problem in this time frame.

Many vehicles with tire pressure monitoring systems or TPMS and sensors in each wheel, have stems designed to last the life of the vehicle. These stems are inspected and only replaced if a problem exist.

Please see our Detailed Topic Dangerous Valve Stems for more information.
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How can I tell how many plies my tires have?

On standard load tires the plies will be listed on the sidewall. There are normally two listings, one for the tread and one for the sidewalls. In the image below, tread is two polyester plies and two steel plies which equal four plies. The sidewalls are two ply polyester. This is considered a four ply tire.

With load rated, truck tires the markings are different. A series of letter ratings designate the ply rating, as follow.

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How can I verify the accuracy of my tire pressure gauge?

There are two primary components to accuracy in tire pressure gauges. The first is repeatability, that is the SAME reading each time. This always precedes the second factor, which is accuracy of the reading. If the gauge does not repeat, accuracy of the reading is irrelevant. Testing repeatability can be as simple as taking multiple consecutive readings from the same tire. Each reading should be the same as the last.

To test accuracy of the reading you must have a known standard. At AGCO, we use a laboratory certified test instrument and check our gauges against it. Best is to locate such a device to have the accuracy of a gauge verified. It is also important to realize, accuracy and repeatability usually changes over time. Very good gauges change very little or none, while poor gauges may not read correctly even when new.
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How do I determine the ply rating of the tires on my light truck?
Ply ratings on LT (light truck) tires are usually expressed by a letter designation, following the size. Common ratings are:
- B for four ply rating
- C for six ply rating
- D for eight ply rating
- E for ten ply rating
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How do tire-pressure monitoring systems, without sensors in each wheel work?

Systems without in-tire sensors use the vehicle wheel speed sensors. A low tire will be shorter than a properly inflated tire. The shorter height means the low tire must turn faster to keep up with the other tires. By monitoring wheel speed, an onboard computer can infer which tire is low.

Please also see our Detailed Topic How To Set Tire Pressure for a great deal more information.
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How do you bleed air from a newly installed power steering system?

In normal cases, fill the system with the proper fluid and leave the cap off the reservoir. WITHOUT STARTING THE ENGINE and with the front wheels off the ground, slowly turn the wheels from right to left and back again several times. Do not turn quickly and do not turn to full lock. Top off the reservoir and repeat until no more fluid is taken in. In more persistent cases it may be necessary to attach a vacuum source to the reservoir while performing the above procedure.
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How does the bead of a tire normally get torn?

Tire beads are almost always torn by improper mounting of the tire. A torn bead is non-repairable and the tire should be replaced. For more information on proper and improper tire mounting, please see our Detailed Topic article Ruining New Tires.
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How does tire size affect the reading of my speedometer?

A taller tire has a greater circumference. That means given the same number of axle revolutions, the vehicle will travel faster than with a shorter tire. The speedometer bases its reading on revolutions and assumes the tire is the correct size. Basically a shorter tire will indicate that you are going faster than you are. A taller tire will cause the speedometer to read slower than your actual speed.

Please see our tire size error calculator where you can compare different size tires and see the effect.
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How likely is it to have four out of round tires on a vehicle?

Out of round in tires is normally a result of poor manufacturing and/or improper tire mounting. Since all tires on a vehicle are often from the same manufacturer and mounted by the same company, it is quite possible.

See our Detailed Topic Out of Round Tires for more information
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How little imbalance will cause a vehicle to shimmy?
This varies a bit based on a few factors. As a general rule, .25 ounce (7 grams) or more will produce a noticeable shimmy. A few factors that affect this include:
- Low profile tires are more prone to shimmy
- Suspensions with more caster and SAI designed in are more prone to shimmy
- Loose suspension parts increase shimmy
- Wheel offset, positive or negative can increase shimmy
See our Detailed Topic Wheel Balance, Shimmy and Vibration for more information.
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How long does it take to rotate tires?
Physically rotating the average set of tires does not take long, perhaps 15 to 20 minutes. Things that can drastically increase that time include:
- not having the wheel lock key available
- aftermarket center caps that are very difficult to remove
- raised or lowered vehicle that are difficult to get on a rack
- resetting tire pressure monitor system (TPMS) sensors
Just resetting the TPMS sensors after rotation can easily take more time than rotating the tires.
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How much pressure do power steering lines have to hold?

Power steering pumps are hydraulic and can produce up to 1200-1500 pounds of pressure. The system operates at much lower pressure, depending on engine speed and restriction to flow. For instance, at an idle and with the steering wheel not turned, pressure may be as low as 250 pounds. With the wheel turned to full lock and the engine speed raised it can approach the maximum.
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How much pressure does it take to straighten a frame?

Most frame machines can exert 10,000 pounds per square inch (PSI) pulling force. Rarely is over 2,500 PSI actually required. Frame and unibody straightening requires surprisingly little force if properly done. The use of brute force is one sign of an unskilled frame technician. Metal has a memory and will return to the shape into which it was formed when properly handled. The factors affecting force required include:

1. The vehicle being properly anchored to the frame machine
2. Use of multiple-simultaneous pulls, rather than single pulls
3. Pulls being set up to reverse the sequence of damage
4. Whether the frame or unibody has had poor previous repair
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How much will a bad alignment shorten tire life?

The extent of tire life that we lose depends on the actual angles that are mis-adjusted and by how much. For instance, improper caster will cause the vehicle to pull one way or the other. As long as all other angles are properly set the effect on tire life will not be drastic. Toe on the other hand will drastically shorten tire life. As an example, for every 1/8 inch of toe a tire will be dragged sideways forty-feet for every mile driven. One-half inch of toe mis-alignment may destroy a set of tires in a few hundred miles. Camber will also wear the tires, but not as drastically as toe.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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How often should I have my vehicle’s alignment set?

Alignment is a repair and not a maintenance item. This means you only need an alignment when there is a problem. A proper alignment usually last several years. In time, suspension components start to wear and the alignment will need to be reset. Also a tire striking something hard enough can cause misalignment.

Replacing certain suspension components, disassembling the suspension for other repair and collision damage can also necessitate alignment correction. Three main symptoms of improper alignment are:

1.) Tire wear on one side of the tire or the other.
2.) The vehicle pulls or veers to one side or the other when driving.
3.) The steering wheel is not straight when driving straight.

Any of the above may indicate misalignment of the suspension or you could experience any combination of the three. If you have none of these symptoms likely the alignment is okay. It is also important to remember that things other than alignment may also cause some of these symptoms.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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How often should I rotate my tires?

Standard tread pattern tires normally do well rotating between 7,000 and 9,000 miles. Predominately highway mileage normally will extend the interval toward longer recommendation. More in-city use normally requires closer to the lower end. All terrain and mud grip type tires are an exception. They may require more frequent rotation when used on paved roads, perhaps 3,000 to 5,000 miles.

For more information on tire rotation, see our Detailed Topics article, Tire Rotation.
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How tight should my wheel lugs be?

There is a specified amount of torque given by the vehicle manufacturer and a preferred pattern for tightening the lugs. The actual torque depends on the diameter, thread pitch and material of the studs.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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I am interested in lifting the suspension on my truck. What type problems might I expect?

Suspension systems are pure geometry. Every angle in the suspension is carefully designed to work with the vehicle at stock height. Raising or lowering the vehicle’s suspension, even a small amount will cause problems. The camber of the front wheels and the roll center of the vehicle are changed. Once changed, the alignment can no longer be properly set and handling will be affected.

Ball joints and control arm bushings are also set to work over a specific range of motion. The stock height puts these components in the center of that range. Raising or lowering the suspension will put them very near their limits. When the vehicle now goes through jounce/rebound cycles, these components are over-traveling their design. Rapid suspension wear, tire wear and poor handling are the normal results.

For a lot more information on modifying vehicle suspensions, see our Detailed topic, Lowering and Raising Vehicle Suspensions.
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I am replacing the tires on my vehicle and want a little more traction. Can I replace them with a wider tire?

Wider tires alone will seldom add traction to a vehicle. Also most newer vehicles have very limited room for the tire to fit. Wider tires may hit fenders and suspension components. A better answer would be to consult a knowledgeable tire salesperson or study each manufacturer’s website for information.

Most tire manufacturer’s make tires in several traction ratings. If traction is a concern, selecting a “stickier” tire from a high quality manufacturer is usually a better answer.
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I bought a new set of tires and now have a shimmy and vibration. The tire store has balanced them several times, but the shake is still there. Another shop checked the vehicle and says the tires are out of round. How do tires get out of round?

Out of round tires are often made that way. Lower quality methods of tire production can produce tires that are simply not round. Beyond that, it is quite possible to ruin a perfectly good set of tires with improper mounting. For more information on improper mounting causing damage to tires, see our Detailed topic, Tire Mounting Problems.
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I bought a new set of tires and the old tires had no uneven wear. Do I still need an alignment?

If the old tires did not wear, the vehicle drives straight and the steering wheel is centered there is no reason to align the vehicle. Alignment is a repair, not a maintenance item. You only need re-alignment when there is a problem with the alignment.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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I bought tires and the shop told me the lug nuts on my car were worn out and should be replaced. Is this a scam?

Lug nuts, especially taper seat type, can wear where the taper meets the wheel. This can be greatly accelerated by over or under tightening of the nuts in the past. Inspecting the lug seat should reveal the wear in the face of the taper. Worn lug nuts can come loose and should always be replaced.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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I do not drive my vehicle very much. Even though the tread is good, I have been advised the tires are eight years old and should be replaced.

Many experts and vehicle manufacturers recommend tire replacement at six years. They also tend to agree that not being driven may present more of a hazard than being driven. This is a problem on vehicle that are not driven daily, particularly motor homes and classic vehicles. I recommend replacing tires at six years, regardless of the tread.

See our Detailed Topic article Old Tires With Good Tread for far more details.
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I do not rotate my tires and they do not wear and seem to last a very long time?

Some tires and vehicles will do fine without tire rotation. Most vehicles tend to wear tires irregularly when they are not rotated. Closely watching the wear pattern on the tires will normally tell which you have. If you are getting good results without rotating, I see no need to change. If there is any doubt, I would go with rotating.

For more information on tire rotation, see our Detailed Topics article, Tire Rotation.
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I find wheel weights are very unattractive on my wheels. Why can’t all of the weights be put on the inside where they don’t show?

There are two phases of wheel balance, static and dynamic. Weight is placed opposite heavy spots and in an equal amount to balance the wheel. Placing all of the weight on one side or the other will balance the wheel in that one plane only. This is static balance and is similar to an old style bubble balancer. For instance if a wheel were like a clock face with no width and had a heavy spot at 12 O’clock, the weight would be placed at 6 O’clock.

The problem is wheels have width and must also be balanced from one side to the other. This is dynamic balance and normally requires weight be added to both sides of the wheel.

See our Detailed Topic Wheel Balance, Shimmy and Vibration for more information.
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I had a flat tire and the tire store refused to repair it because the tire was seven years old. Do I have any recourse?

Tires have a life and become unsafe with age. The adhesives that hold them together fails and the rubber degrades. This is so even though they may still have good tread remaining. I know of no tire company that will warranty a tire after six years. The tire company is being prudent in refusing to repair a tire that may not be safe to operate. I would advise replacing any tire over six years of age.

See our Detailed Topic article Old Tires With Good Tread for far more details.
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I had a suspension noise on bumps and had the front McPherson struts replaced. The noise is still there, could it be a bad strut?

Anything is possible, but two struts with the same noise would be extremely unlikely. More often the problem is with another component and was mis-diagnosed. Upper strut mounts often cause a bumping noise in the strut area.
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I had the intermediate steering shaft replaced on my Suburban for a clunk noise in the wheel. A few months later the noise returned. Could it be a bad shaft?

We have found the lower bushing in the steering column is often damaged by the bad shaft. Replacing the shaft moves the bushing and temporarily stops the clunk. A permanent fix normally involves replacing the bushing and the shaft.
For more information please see our detailed topic GM Steering Column Clunk.

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I have a loud knock noise under my Ford Sport Trac and was told the frame to body cushions are bad. Shouldn’t these cushions last the life of the vehicle?

Body mount cushions have traditionally lasted the life of most vehicles. In my opinion, the problem with the Ford Explorer and Sport Trac is caused by substandard material.

For more information on Ford body cushion problems, see our Detailed Topic Ford Explorer and Sport Trac Frame/Body Cushions.
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I have a sports car and am very concerned with air pressure. What is the best tire pressure gauge I can get?

We have done a considerable amount of air pressure gauge testing and find the PCL, Accura I, to be the finest gauge we have ever used, by a wide margin. Accurate, easy to use, very heavy duty and can measure a wide range of pressure with precision.
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I have a vehicle with very high milage [200,000] and need to replace the rack and pinion. I have replaced most parts of the front suspension except the lower control arm bushings. How long do they last?

Some go out at low milage, others last the life of the vehicle. A careful inspection is in order. If the bushings are not deteriorated, off center or dry rotted I see no reason to replace them.
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I have a wobble in my steering wheel that starts when the car starts to roll. At about 10 to 15 MPH it is very noticeable but gets better at higher speed.

Very obvious wobbling at low speeds is often a sign of a separated tire. This is a condition where air leaks from the air chamber and separates the adhesive that holds the plies of the tread together. This often creates a large bump in the tread which causes the wobble.

As the tire increases speed, the wobble turns into more of a vibration. The condition is very dangerous as the tire can fail unexpectedly at any time.

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I have been told I should balance my tires every time they are rotated for best life, what is your opinion?

Rotate and balance are two totally separate services. Rotation is maintenance, that is something done for low cost that prevents a higher cost problem. By rotating tires, the wear is more evenly distributed and the tires last longer.

Balance on the other hand is a repair, in my opinion. A quality set of tires, properly balanced, with the correct weights should stay balanced. The exceptions would be if a balance weight comes off or if the tire is removed from the wheel.

This is a good example of overall lowest cost. It is less expensive to do business with a shop that has precision balance equipment, all the proper wheel adapters, and a large selection of wheel weights. Even though the initial PRICE of balance in such a shop may be higher, the COST is much lower because it does not have to be redone.

Rotate tires for best life, but get a good balance the first time on a quality tire. This way you can save the expense of balancing every time you rotate.

See our Detailed Topic Wheel Balance, Shimmy and Vibration for more information.

For more information, on a Overall Lowest Cost see the AGCO category, under AGCO Philosophy.
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I have been told if I use the temporary spare tire, I must put it on the back only (i.e., if a front tire goes flat I need to put a back tire in its place and put the spare on the rear.) Others say this is a myth. What is the official answer?

Actually both are correct, in a way. First, the spare tire is strictly an emergency item, not intended to be used for any length of time. Maximum safe operation is normally under 45 MPH and for short distances only [20-30 miles.]

With the shorter spare tire on the front, the differential gears are forced to turn very fast. This because the shorter tire must turn faster to keep up with the taller one. This can quickly damage the transmission/differential.

Now, with the intended use of just getting to a place for immediate service [two to ten miles,] there would be little problem putting it on front. The further driven the greater the chance of a problem. It would always be better to put it on the rear, from that respect.
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I have been told my Ford Expedition needs cams installed before it can be aligned. Is this true and why is it built that way?

Many vehicles require some addition or modification to facilitate alignment. If the caster and/or camber is out of specifications on your vehicle, it may need cams installed to correct this problem. Vehicle makers can now manufacture vehicles that are properly aligned. If they were built adjustable, each would require a full alignment after manufacture. By building them in alignment and making them non-adjustable they can skip this step, saving money.

Manufacturers also realize that in time the vehicle may require adjustment and many sell additional parts that make this possible. This is the case with your Expedition.

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I have had my car aligned several times and the steering wheel is not centered when driving straight.

Centering the steering wheel is a very basic part of an alignment. If the wheel is not centered, the vehicle is not aligned, in my opinion. If the steering wheel is always off in the same direction and by the same amount, this is a simple adjustment. If the amount or position changes, there is something moving in the suspension. In either case, the alignment shop should correct this or let you know what is wrong.

On vehicles with rack and pinion steering, the rack bushings can slip if they are worn or oil soaked. If the rack moves, even very slightly, the steering wheel will move off center. Adjustment bolts left loose or worn components will have the same effect.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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I have replaced the inner tie rods on my vehicle three times in 60,000 miles. What could be the cause?

If quality replacement parts are being used, you should check for any type of vibration. A shimmy in the steering, caused by an out of round or out of balance tire can quickly destroy suspension components. If there is no shake in the wheel, inner tie rod failure can also be caused by current flow from the engine to the body. Transient current flow can take a path from the engine, through the transmission and drive axles to the steering knuckles. The knuckles connect to the tie rods and are ultimately grounded through the steering mechanism.

Please see our Detailed Topic Transient Current Flow for much more information.
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I heard there was a recall on tire valve stems, how can I check to be sure mine are okay?

Valve stems manufactured for Dill between August 2006 and November 2006 were the subject of a recall. The model TR413 and others were involved. It is difficult to identify these stem, without removing the tire from the wheel. Rather, I suggest treat all valve stems as a potential problem. That is, inspect them when tire air pressure is checked. Simply push the stem toward the wheel and check for cracks at the base of the stem. ANY stem showing cracks should be replaced.

See our Detailed Topic Dangerous Valve Stems for more information.
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I just bought a new vehicle and the tires are marked maximum pressure 44 PSI but the owner manual says 32 lbs front and 30 lbs rear. What pressure should I use to maximize the life of my tires and safe handling?

The maximum rating listed on a sidewall is the highest pressure that should be put into the tire and not a recommendation. The vehicle manufacturer considers ride quality at least as important as tire wear, so gives a lower rating.

You may consider one he maximum the other the minimum that should ever be used. I find better tire life is normally achieved at about 10% less than the maximum. This pressure will rise slightly if the tire gets hot [extended driving] and will drop when the ambient temperature drops significantly. Unless temperature change is substantial [50'F or so] it is normally not a crucial factor. Also see our tire pressure article for a great deal more information.
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I lost the key to my wheel locks. How can I get the wheels off?

A number of tools are available to defeat wheel lock and most shops that service the suspension, and tires will have them. If it is not an emergency, you may also be able to order a replacement key. If the locks are original equipment, the part department of the vehicle manufacture's dealership can order it for you.
For more information, please see our Detailed Topic, Wheel Locks.

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I recently bought tires and was told the valve stems on my vehicle should not be replaced. Is this correct?

Vehicles built after 2007 and vehicle with tire pressure monitoring systems (TPMS) often use sensors that are part of the valve stem. These stems are designed to last the life of te sensor, usually seven to twelve years.

See our Detailed Topic Valve caps and TPMS for more information.
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I replaced the rear air suspension bags on my Lincoln and now the rear is too high and will not come down.

There are several possible causes. One is the height sensor in the rear. If it does not work the vehicle may not bleed air pressure to lower. Another possible cause is the exhaust solenoid in the pump. If the solenoid does not work, air pressure will not be bled off. This solenoid may have been bad and unnoticed when the bags were leaking. The leaking bags serve to bleed excess pressure. Other causes include the solenoids in the bags, though this will normally result in a leaning vehicle unless both fail. Finally the air suspension computer may not send the command for any of the above solenoids to open. Least expensive is to have someone with the proper tooling and experience diagnose which condition exist.
For more information please see our Detailed Topic Ford Air Suspension Problems.

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I struck a curve and blew out a tire. The wheel, tire and front struts were replaced, but the alignment could not be set because there was no adjustment. Can anything be done?

Yes, a full service suspension shop with frame equipment should be able to diagnose and repair the problem. Many vehicles built today have little or no adjustments. This is because they are manufactured “in alignment” and will remain so, unless something wears or is bent.

Diagnosis is the key and once the bent or worn parts are identified they can be replaced or repaired with specialized equipment. Once the vehicle is dimensionally returned to specifications the alignment will also be correct as it was designed.
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I take very good care of my tires, but the treads have come apart on three of the four?

When the treads separate from multiple tires in a set, the problem is normally age or a defective product. We feel six years is the safe age of a tire. Failure in old tires may be quite common, even though they still have good tread. Because of the good care, your tire tread may have lasted well beyond the useful life of the tire.

For more information on tire age, see our Detailed Topics article, Old Tires, Good Tread.
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I want to install a larger set of mud grip tires on my truck. Will this affect the computers?

The various computers on the vehicle do use vehicle speed in their calculations. A larger tire has a greater circumference. This means it travels further for each revolution. Sensors calculate vehicle speed based on the number of revolutions and assume the circumference of the tire is correct. If the tire changes, the calculations are wrong, resulting in incorrect data being used.

Please see our tire size error calculator where you can compare different size tires and see the effect.
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I was told a tire was causing my car to pull. The term used was conicity. Can camber or caster be adjusted to compensate?

Conicity is considered a defect in a tire. The effect generally will vary with the speed driven. For instance, hardly noticeable at low speed to quite prevalent at higher speed. If alignment were used to compensate at high speed, the vehicle would pull the other way at low and vice versa. Further, when the tires were rotated or replaced, the alignment would need to be reset. The proper repair is to replace the bad tire(s) and set alignment correctly.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.
For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.

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I was told my rack and pinion was bad, but I have no symptoms?

Some of the symptoms of a bad rack and pinion can be subtle, especially at first. For instance a leak past the rack seal may be contained by the rack and pinion boots. This may show no leak and may not drip under the vehicle for several months. Eventually there will be noise from a low power steering pump and you may have to add fluid. Another issue could include slack in rack and pinion components. Eventually tire wear will result, but initially may not be noticed. A second opinion may be also be very useful, if you doubt the original diagnosis.
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I was told my tire was separated, what does that mean?

Separation is a condition where the adhesive that holds the plies of the tire together breaks down. This often creates a large bump in the tread which can cause a wobble or a hard pull to one side. The condition is very dangerous as the tire can fail unexpectedly at any time.

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I was told the yellow dot on the side wall of a tire should be aligned with the valve stem. My new tires have a yellow and red dot, what does that mean?

The yellow dot normally indicates the lightest point on the tire and is aligned with the valve stem. The valve stem is normally the heaviest point on the wheel. The red dot is more complex. If the tire has both, ignore the yellow dot. The red dot is basically the point of maximum road force variation, first harmonic. While not exactly, this might be thought of as the stiffest point in the sidewall.

Some steel wheels have a dimple to mark the lowest spot in the wheel. If so, the red dot aligns with the dimple. If not, or with aluminum wheels, it is placed at the valve stem.

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In an emergency stop I locked up the brakes on my vehicle. After that I noticed a distinct vibration when driving. The tire store says the tires are flat-spotted. What does that mean?

Flat spotting refers to rubber being worn away in one area of a tire. This normally results from sliding the tires on rough pavement, such as a lockup stop or sliding sideways. Flat spotting is not correctable and the affected tires should be replaced to avoid vibration damage to the vehicle.

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Is a frame heated when it is straightened?

Heat is very rarely and very judiciously used by a professional. Even when used it is only on certain areas and for a very limited time. This heat is normally less than 500 degrees Fahrenheit and monitored with heat crayons. When a vehicle is properly anchored and multiple, simultaneous pulls are used, heat is normally not required. Instead a procedure known as stress relieving is used.

Most newer vehicles use high strength steel (HSS,) high strength low allow (HSLA) and martensitic steels. These high-tech steels can quickly be ruined by heat application.
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Is a road hazard warranty on new tires worth the money?

Road hazard is like a term insurance policy. As the tire wears the amount paid on the claim is steadily reduced. I insure against risk I cannot afford to take, for example, liability on an automobile. Replacing a tire may be aggravating, but it is not likely devastating. I see no sound reason to pay someone to cover such a risk.
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Is buying tires online a good idea?

Buying tires is a bit different than buying many other things online. Tires have a long life and require service during that life, for instance tire rotation and flat repairs. Many times these services are included in the price you pay locally, but obviously not in an online purchase. Adding these costs to the online tire price may make them comparable to locally purchased tires.

There is also the issues of finding someone to mount and balance the tires. Shops normally charge a premium when they do not sell the tires. The shop mounting the tire is liable for mishaps in mounting, and they made no profit on the tire to help offset the cost.

If a tire should fail there is also a problem. The failure will have to be diagnosed, then the tire removed and something put in its place. With online tires, the problem tire(s) must normally be sent back to the original seller for adjustment.

Like most things in life assuming more risk may save some money. If you allow money for the risk you take and the inconvenience, you may well be able to purchase the tires at full retail locally.
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Is it better to move an out of balance tire to the rear?

Mechanically there will be little difference. The vibration will simply damage rear components rather than front.
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Is it possible for a vehicle with a proper wheel alignment to still pull to the right or left?

Many things other than wheel alignment can cause a vehicle to pull when driven. A dragging brake may cause a vehicle to pull. Binding or bent suspension parts can also cause memory steer, or a pull in the direction turned last. Tires that do not match, side to side or low air pressure on one side also causes problems. Even with new, matching tires, conicity can cause a pull in a properly aligned vehicle.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.

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Is it possible for two tires have the same serial number?

Serial numbers are normally attached to batches of tires and not individuals. The serial number is part of the longer Department of Transportation or DOT number. This series of numbers and letters identifies the month and year of manufacture along with several other pieces of information. The DOT number is the same for all tires in a given batch.
To learn how to read a tire date code, please see How to read a DOT number.

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Is it possible to weld cracks in a unibody vehicle?

Successfully welding unibody components requires a knowledge of metallurgy and welding. High strength low allow (HSLA) and Martensitic steels are widely used in modern vehicle construction. Improper welding can easily destroy these metals. Welding must be performed so that heat affect zones do not overlap. Reinforcing the welded areas can also cause stress risers. These can cause future cracking in other areas, due to changes in the flexibility of the repaired member. For all of these reasons, repairing cracks in a unibody should be left to a frame repair and welding specialist.
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Is it true that plugging a tire with a string type tire plug will void the warranty and if so, why?

String type tire plugs do not meet industry repair standards and may void the warranty on tires. Failure to completely seal the puncture can allow air to force its way between the plies of the tire. When air gets between the plies, it causes them to separate from one another. This condition is known as a tire separation, is very dangerous and leads to tire failure.

A proper repair involves removing the tire from the wheel and vulcanizing a patch to the inside. This seals the air chamber from the plies and belts that make up the tire. The best method involves a patch that also has a stem manufactured on it. The patch seals the air chamber while the stem seals the original path of entry.
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Is steering wheel shimmy a symptom of my rack and pinion wearing out?

More likely a worn out rack and pinion is a symptom of steering wheel shimmy. When tires/wheels shimmy, they place a good deal of force on suspension components, such as the rack and pinion, tie rods, struts and ball joints. Shimmy from an out of round tire or bent wheel causes wear. Excess slack from worn parts may allow shimmy to manifest more severely, but such wear is more the symptom than the cause.
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Is the body of a vehicle removed to straighten the frame?

To the contrary, all sheet metal should be left in place. As damage occurs it travels through the frame and body. With everything in place, and using the proper method, the damage can be reversed. Removing parts will change the rigidity of the structure. This makes it far more difficult to properly repair and secondary damage is often not corrected in the initial pulls.
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My cars pulls when driving. It may pull right and then pull left and then right again and so on. The tire store told me this was impossible, it was just the roads. Do you have any ideas?

You could a condition called memory steer. That is the vehicle tends to remember the last way it turned and pulls in that direction. Confirmation is relatively simple. Drive the vehicle and note which way it is pulling. Make a hard U-turn in the opposite direction and see if the pull changes to the direction of the last turn.

Once the existence of memory steer is confirmed, the diagnosis of the cause can begin. It will generally be a binding component in the suspension but can take a good deal of expertise to locate. On vehicles with McPherson struts on the front, binding strut bearings are a common cause. The bearing binds when the strut rotates. This causes the coil spring to twist and then jump, rather than smoothly rotating. On a hard turn the spring does not return to a full center. When trying to drive straight the spring is slightly twisted, causing it to pull the steering in the direction of the last turn.
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My Chevrolet Silverado has the typical steering column clunk. Does this affect my wheel alignment?

Steering column clunk is annoying, can damage the lower column bushing but will not affect wheel alignment.
For more information on steering column clunk, please read our Detailed Topic GM Steering Wheel Clunk.

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My Lincoln Town Car squats down in the rear at night. Strangely when I start it in the morning it levels out again. What do you think would cause this?

The Town Car is equipped with rear air suspension. Two air bags support the rear and height is regulated by a computer controlled air pump. Each bag has a solenoid that prevents leakage. A third solenoid in the pump further prevents leakage. If the vehicle only drops after sitting (over night) the likely cause would be leaking rear air springs. When you start the vehicle, the air pump inflates the springs and so the vehicle rises. Continued operation with the springs leaking, will damage the pump and can cause severe damage to the system. The rear air springs should be checked and replaced to prevent additional expense.

See our Detailed Topic article Ford Air Suspension Problems for far more details.
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My new tire has a dimple in the sidewall, an area that dents in. The tire store says it is not a problems should I be concerned?

Dents in the sidewall of new tires are sometimes called undulations. They occur where the plies are spliced together. Most experts agree they pose no danger to the tire and are cosmetic only. This is NOT the same as an area that dents outward and does represent a problem.

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My new tires have a small red dot on the sidewall. Does the red dot mean anything?

The red dot is painted on by some manufacturers after tire production. It shows the point of maximum radial force variation. This is roughly the same as the stiffest area of the sidewall. It is somewhat like the highest point in the tires, though not exactly. The red dot is normally aligned with the valve stem, during tire mounting. The valve stem shows the heaviest point of the wheel. This way the area with maximum variation may be partially counteracted by the heavier part of the wheel.
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My new vehicle pulls to the right when I drive. The dealership told me the alignment is within specifications and it pulls because all roads lean to the right for drainage. Does this sound correct?

All roads do lean, but not always to the right. They lean towards the drainage area which is often on the right. Some roads also lean to the left, when the drainage is on that side. Because most roads lean right, alignment is normally set to compensate for this. This allows the vehicle to drive straight on the majority of roads.

If the pull is annoying and consistently to the right on all roads there is likely another problem. The alignment needs to be confirmed on a known accurate machine. If the alignment is not the cause, the tires should be crossed and the vehicle driven again. If the direction of the pull changes, you have a tire problem and this must be resolved before going on.

If the pull persist, the tires are okay and the vehicle is equipped with power steering, the steering should be checked for power steering lead. If that is not the problem, dimensional accuracy of the suspension should be verified by a frame shop.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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My owner’s manual states 30 PSI pressure for my tires and I am careful to maintain this. The first set of tires wore properly, but my next set is wearing on the shoulders. The tire shop says my tires are under-inflated.

Tire pressure serves several functions and is dependent on load and tire design. For best tire wear I recommend staying about 10% under the maximum pressure listed on car tires. This pressure will be specified somewhere on the tire’s sidewall.

The tires that came with the vehicle may have had a designed maximum inflation pressure of 35 PSI. The vehicle manufacturer is normally conscious of ride quality and specifies 30 PSI to improve ride. This extra 4% reduction will increase the smoothness of the ride, because it allows the tire to absorb bumps.

Many newer tires have designed maximum pressures of 44 PSI and higher. Running these tires at 30 PSI can cause tire wear. I would recommend starting at 10% under maximum or 40 PSI. If the ride feels too harsh, you can reduce this but never below the amount specified by the vehicle manufacturer. Reduction of pressure normally results in more wear on the shoulders of the tires. This method works on passenger or P-rated tires. For truck or LT rated tires a different method is needed. Please see our tire pressure article for a great deal more information.
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My tires are worn out, should I replace them before I have the vehicle aligned?

Many alignment shops like to see the wear on the tires so they can “custom” align the vehicle to address your specific needs. On the other hand, the final alignment should be set with the new tires on the vehicle. Buying your tires and alignment at the same place will greatly simplify this process. Also if there is a problem in the future, there is only one place to deal with. The key is to buy tires from a place capable of solving problems you may encounter.

See our Detailed Topic Ruining New Tires for more information.
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My tires keep going out of balance. I have had them balanced several times but my steering wheel still shakes.

Tires do not go out of balance, either they are not being properly balanced or there is another problem causing the shake. When you ask for wheel balance, you inadvertently have [improperly?] diagnosed the problem. The best shops will not accept such a request and insist on having the symptoms. This allows them to provide the proper fix for the problem.

Many things can result in shake other than tire balance. Find a shop that asks for symptoms, rather than accepts service request. Asking for a technician to ride with you and demonstrating the shake, will greatly aid in solving the problem.
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My truck keeps breaking the transmission mount. Within six months of replacement it breaks again. Is this just bad parts?

Some replacement mounts are of very low quality. Continually breaking mounts, sounds like you may have another problem. As a test, remove the mount and support the transmission instead with a block of wood. Run the engine for a few moments and let everything settle. If the transmission moves out of alignment, it is possible the engine is not properly aligned to the chassis. Bent or even bad engine mounts are a possible cause as well as frame damage.

See our Detailed Topic Frame Repair, The Good, The Bad and The Ugly for more information on hidden chassis damage.
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My vehicle does not have a power steering pump, how does the power steering work?

Many vehicles use electric motors in the steering column to provide power assist. These systems are electrically powered and do not use a conventional power steering pump.
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My vehicle has always driven straight. I replaced the tires and now there is a pull to left when driving. Could the alignment have suddenly changed?

Assuming the air pressure in all tires is correct, more likely you are experiencing radial tire pull, also known as ride-disturbance and conicity. This is the tendency of a radial tire to pull or lead to one side. With ride-disturbance the pull normally gets worse as speed of the vehicle increases.

Diagnosis is simple and straight forward. Verify the direction and intensity of the pull by driving. Temporarily cross the front tires; move the left front to the right front and vice versa. Drive the vehicle again and see if the direction of the pull has changed. If so the tires are the likely cause as nothing else has changed.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.

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On a vehicle, what is the difference between a chassis and a frame?

The two terms are used interchangeable to describe a separate structure that supports the body of a car or truck. The word chassis may be somewhat older and less used today. Both terms are sometimes incorrectly used to describe supporting structure of any vehicle. Many vehicles built today are unibody construction, not using a separate structure to support the body, thus no frame or chassis.
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One wheel on my vehicle keeps coming loose. Last time, I tightened the lugs more than normal, but it still came loose. What could cause this?

In almost every case, wheels that get loose are related to damaged lug holes in the wheel. Damage occurs when wheels are run loose or over-tightened. Once the taper of the lug seat is damaged, it will no longer retain the lug nuts. This is very dangerous and can result in lug stud breakage. The wheels should be checked and replaced if this is found to be the case.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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Pricing aftermarket wheels I find they are much less expensive than the originals, is there a quality difference?

Original equipment wheels are normally of high quality and are specifically designed for the suspension in use. Of the many factors to be considered are those that are familiar such as diameter and width. Wheel offset, whether the wheel is hub or lug centered, lug seat type and the type of construction are also important.

As a general rule original wheels are forged or cast and machined. Machining produces a wheel that runs true. The center hole of and original wheel is the correct diameter to center the wheel perfectly on the vehicle. The offset [relative position of the mating surface to the center of the wheel] is matched to the suspension. There are usually full provisions for dynamic balance and the lug mount surfaces are often hardened or sometimes have hardened inserts.

Some cheap replacement wheels may be cast or stamped, rather than machined. This may produce a wheel that does not run true. Strength of the wheel may be compromised and corrosion can be an issue, if substandard alloy is used.

Original equipment wheels normally run true on the vehicle and give much better overall results than aftermarket replacements. If replacement is considered all the above factors should be considered.
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Recently I damaged a tire. The other three tires have about 50% tread remaining. The tire store insisted on putting the new tire on the rear. I think it should go on the front?

I agree with the tire store. Whenever less than four tires are put on a vehicle, the new tires should go in the rear. This offers better vehicle control. In the case of one tire, there is also a high probability of the vehicle pulling to one side or the other if the front tires have different amounts of tread. By placing the new tire on the rear, the vehicle is safer and will likely drive better.
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Should a torn boot on the rack and pinion be replaced immediately?

Rack and pinions are expensive components to replace. When the boot tears, contaminants will enter the unit and cause it to fail. The boots can be replaced at relatively low cost and can prevent rack and pinion failure. I would replace any torn or dry rotted boot immediately to prevent further expense.
For more information, please see our Detailed Topic, Properly Checking Tie Rod Ends.

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Should I buy road hazard warranty on new tires?

In my opinion, road hazard is an overpriced, decreasing value insurance policy. Insurance is better suited to risk we cannot afford. An example might be liability insurance. Because we cannot afford the risk, we pay someone else to assume part or all of it for us. This is expensive but better than the alternative. Losing a tire will rarely wipe anyone out financially. Assuming the small risk normally saves far more than any gain.
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Should lug studs be lubricated when installing lug nuts?

I am unaware of any manufacturer that suggest lubricating lug studs. The specified torque is for a clean, dry stud. Torque is a measure of resistance to turning and not actual clamping force. Lubricating the studs lowers the resistance to turning and the clamping force will be much greater than specified, when the proper dry torque is applied. This could result in damage to the wheels, stretching the lug studs and stripping the treads.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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The air pump on my Lincoln Town car seems to run a lot, do you think the pump is bad?

If the pump runs more than normal, the system has a leak. When we lose air pressure, the pump runs to replace it. The most common source of leakage is the rear air suspension bags. They tend to dry rot and crack and we lose air pressure. Quick action is important as the pump will be damaged by running too much. This adds considerable unnecessary expense to the repair.
For more information, please see our Detailed Topic Ford Air Suspension Problems.

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The motor on my General Motors electric power steering had to be replaced. Should I have the wheel alignment checked?

The motor on GM electric power steering is part of the steering column and does not affect the wheel alignment. On vehicles where the motor is part of the rack and pinion, it could and a wheel alignment check would be in order.
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The steering wheel does not point straight when I drive straight. I had a wheel alignment and the wheel is still crooked. What could cause this?

A centered steering wheel is the result of properly setting toe, front and rear. With a proper wheel alignment, the steering wheel will be centered. A steering wheel that changes center is another matter. If the amount the wheel is off changes, something is moving, often the rack and pinion mount bushings. If the amount the steering is off center, is constant, alignment is not being properly set. Perhaps the standards of the alignment shop may not be as high as you might like.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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The steering wheel in my vehicle shakes back and forth when I reach about 45 mph. It seems to go away at other speeds, do you think the alignment could be the cause?

The alignment is a very unlikely choice. Shimmy in the steering wheel is normally associated with something that is rotating, such as a tire or wheel. You will feel the symptom of shimmy in certain speed ranges. When the frequency of the vibration matches the frequency of the vehicle structure, the problem will show up. Likely causes include, out of balance tire(s), out of round tire(s), bent wheel(s) or any number of other rotating parts. Important is to give the shop the symptom, rather than requesting a service such as alignment or balance. In this way the likelihood of diagnosing and correcting the problem is greatly enhanced.

For even more information on wheel alignment, see our Detailed Topics article, Wheel Alignment Myths.
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The Z rated tires, recommended for my vehicle, are very expensive. Can I use a lower rated tire if I do not drive fast?

The speed rating on tires has to do with the centrifugal distortion the tire can withstand. Using a lower rated tire is not recommended and may adversely affect braking and handling.
For more information on speed ratings, please see our detailed topic, Can I Substitute A Lower Speed Rated Tire.

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There is a clunking noise in my Silverado steering wheel. It sounds like something is loose but everything appears to be good.

The Silverado, Sierra, Tahoe, Avalanche and Suburban, as well as many other GM vehicles have a problem with steering column clunk, much as you mention. The intermediate steering shaft is the root cause, but if it continues, the lower steering column support bushing may also be damaged. Repair normally involves replacing the lower bushing and the intermediate shaft with an updated shaft.
For more information please see our detailed topic GM Steering Column Clunk.

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This is very strange, but my Chevrolet pick up truck wears the rear tires to the inside. This occurs quickly, about 10,000 miles and has happened on two sets of tires. I am told this is not possible as there are no adjustments possible.

The rear differential of this vehicle is a single piece housing and is not adjustable. That does not mean it cannot get out of alignment. Like any piece of metal, rear differential housings can bend. When they bend, the alignment of the rear wheels are disturbed. Inside tire wear normally indicates either negative camber and/or toe out between the wheels.

Depending on the position and severity of the bend, these housings can sometimes be straightened. If not, the housing can be replaced, reusing your present gears and possibly axles.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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Tire wear, inflation pressure and misalignment

While improper alignment is a major cause of tire wear, inflation pressure is also very critical. Many people are confused what the proper pressure may be. The sidewall of the tire list one pressure and the vehicle manufacturer may list another. Which is the proper pressure? I think the answer is neither. The proper pressure depends on the desired affect. For instance, the vehicle manufacturer wants the vehicle to ride well. Their recommendation takes this into consideration. If ride is the main concern, this may be the proper pressure. The problem is, it may also allow for some tire wear. The manufacturer's recommendation should be considered the minimum allowable on passenger cars. The pressure on the sidewall of a passenger car tire, is the maximum amount the tire will hold and not a recommendation. I have found very good results by inflating to 10% under this maximum. For instance 40 PSI in a tire that says 44 PSI Maximum. Next watching the tire for signs of wear and adjusting within these given limits allow for fine tuning. If the ride is a little rough decrease pressure slightly. If there is too much shoulder wear increase pressure, staying within the above limits.

An under inflated tire will wear on the shoulders more than in the center of the tread.

By contrast, an over inflated tire wears the center of the tread more than the shoulders.

A properly inflated tire wears evenly across the tread.

Of course other things can cause tire wear as well. Alignment wear will normally be on one side or the other. This differs from under inflation as the tire is not worn on both sides. The tire below has a good deal of tread on the left, but is ruined because of the wear on the right.

This wear could have been prevented by a proper alignment. This 60,000 mile tire lasted about 15,000 before having to be replaced.

Certainly there are other things that contribute to tire wear as well. Also see our tire pressure article for a great deal more information. If you have any questions, let the professionals at AGCO check and advise you. AGCO, it's the place to go!
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What are the benefits of rotating and balancing tires?

Rotation and balance are separate items. Rotation is maintenance and helps even out tire wear between the tires. Front tires tend to wear on the outer edges, because they are turned during steering. Rear tires tend to wear in spots, because the rear on most vehicles are considerably lighter than the front. Rotating tends to even this wear among all four tires.

For more information on tire rotation, please see our Detailed Topics article, Tire Rotation.

Balance involves placing weight on the wheels to counteract imbalance in the tires. If the tire is properly balanced when it is first installed [mounted] it should not require balance again. An exception is if the tire is removed from the wheel or a weight comes off.

For more information on wheel balance, please see our Detailed Topic Wheel Balance, Shimmy and Vibration.
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What are the signs of bad rack and pinion mount bushings?

As with most things, the symptoms depend on the nature and extent of the failure. An early sign is often a feeling of slack in the steering. A bumping or knocking when turning the wheel can also result. As the bushings get worse the steering wheel will not stay centered. Eventually shimmy in the steering and tire wear can result.
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What are the symptoms of a bad McPherson Strut?
There are several ways in which a strut may fail or need replacement:
- Most common is leakage. A small film of oil around the shaft is normally not a problem. Fluid covering several inches of the strut or dripping off indicates a need for replacement.
- Noise, particularly on bumps, and coming from the strut is another problem indicating need for replacement. This should be carefully diagnosed, as good struts are replaced quite often due to mis-diagnosis of noise source complaints.
- Ride quality is somewhat subjective but excessive bouncing and diving of the suspension is another symptom of worn struts.
- Finally, struts are sometimes bent from pot holes, striking curbs or other impact to the wheel. This will affect wheel alignment and normally cause tire wear.
For more information, please see our Detailed Topic, How Do You Know When You Need Shocks or Struts
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What are the symptoms of a bent wheel?

The most common symptom is vibration, much like an out of balance tire. This will continue even though the bent wheel may be balanced. Balance and being round are different factors. Other symptoms sometimes include losing air pressure, worn suspension components, scallop wear on the tire and/or noise when rolling.
See our Detailed Topic Wheel Balance, Shimmy and Vibration for more information.

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What are the symptoms of a tire with a broken belt?

A broken belt will normally cause a vibration as the tire is no longer being held in a round condition. Often there may also be a wobble felt at low speeds and many times the vehicle may start to pull, if the tire is on the front. Inevitably the tire will fail, many times resulting in a blow out.
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What are the symptoms of an out of balance tire?

The leading symptom will be vibration when traveling at speed. Normally a shimmy in the steering wheel shows a front tire out of balance. A vibration in the entire vehicle is more likely a rear tire. Vibration from a wheel out of balance will normally come and go with vehicle speed. For instance a vibration at 45 MPH and not at 65 MPH or vice versa. Two clues of improper balance, when looking at the wheel are, no weights on one side or the other or more than one weight on either side. No weight can show static balance only or that the weights have come off. Multiple weights on one side of the wheel shows operator error.

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What are the symptoms of bad ball joints?

Symptoms will vary depending on the type and severity of the failure. When the protective grease boots fail, grit and grime enter the joint. At this point symptoms may range from none to squeaks when turning and hitting bumps. As the wear progresses, slack develops and the wheel alignment will change. At this stage, tire wear, shimmy and slack in the steering may result. In the case of catastrophic failure the joint can pull apart and the wheel may separate from the control arm. This is extremely dangerous as we can lose control of the vehicle.

See our Detailed Topic All About Ball Joints for more information.
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What are the symptoms of bad tie rods?

Symptoms can range from none at all to a shake in the steering wheel to tire wear. Improperly checking tie rods by squeezing them can also damage a good end. Proper inspection involves pushing in and out on the wheel while watching the joint for side to side movement.
For more information, please see our Detailed Topic, Properly Checking Tie Rod Ends.

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What causes cracks in the sidewall of tires?

A leading cause of tire cracking is age. Many experts and vehicle makers state six-years is the maximum safe life of a tire. Please see our Detailed Topic article Old Tires With Good Tread for far more details.

Use of tire dressing can also promote cracking of tires. Some tire dressing may remove the ozone protection from the rubber. Severe cracking at low age is usually a defect in the tire, a deficiency in manufacturing.

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What causes tire noise?

Noisy is a pretty generic term. There are several different types of noise that tires may make and different causes for each noise. For instance a whining or singing type of noise is usually related to the tread pattern design. Engineers sometimes allow more noise to get other benefits. An example would be a mud-grip tire. All terrain tires are much noisier than a highway tread, but far better for off-road use.

A thumping or slapping noise when rolling is often associated with an out of round tire. This is because the out of round tire bounces as it rolls. This may also cause a vibration and damage to the suspension. Please see our Detailed Topic Out of Round Tires for more information.

A roaring noise, similar to a mud-grip tire or bearing type of noise is usually caused by tire wear, often called chopping. This is where the tread is worn is spots. The wear causes a rough surface, which can be felt with the hand. This wear can be caused by mis-alignment of the suspension, bent or worn parts or even a bad tire.

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What causes tires to make a roaring noise?

Abnormal tire noise is normally caused by wear. Bent or loose parts, particularly on the rear, can cause tires to wear in spots. Often called chopping, such wear causes the tire to produce a mud-grip type roaring noise. A professional should be able to check the wheel alignment and identify the cause.

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What do the size numbers on my tire mean?

Most passenger vehicle tires sold in the US employ the P-Metric size system. This is an alpha-numeric code which defines the tire size such as P255/60R17. The P means passenger use, the 255 is the width in millimeters at the widest point. The 60 is the aspect ratio and in this example means the tire sidewall is 60% as tall as the width. The R indicates radial construction and the 17 is the diameter of the wheel the tire is made to fit.

There are also letters that indicate the "speed rating" which is how well the tire can resist centrifugal force. Load ratings which tell how much weight the tire can support, as well as a traction, temperature and wear rating. A maximum inflation rating will also be present.

The number beginning with "DOT" indicates information identifying the tire with the last four digits indicating the week and year the tire was built. For instance if the last four digits of the DOT number are 2512, the tire was built in the twenty-fifth week of 2012.
For more information on speed ratings, please see our Detailed Topic, Can I Substitute A Lower Speed Rated Tire.

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What does air suspension mean?

Air suspension is a system that replaces some or all of the conventional coil and torsion bar springs with springs that are supported by air. The advantage to air suspension is improved ride and the ability to adapt to varying weight loads. This allows the vehicle to better stay level, regardless of the load. Many vehicles use air suspension in the rear only and conventional suspension in the front. Others use air suspension on all four wheels.
For more information please see our Detailed Topic Ford Air Suspension Problems.

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What does it mean when a vehicle is said to be dog tracking?

Dog tracking is often used to describe the front and rear wheels not traveling in line with each other. Many things can cause this, from poor wheel alignment to a bent chassis. When the moving vehicle is viewed from behind it appears to be moving sideways, sort of like a dog with its hind legs out of line with the fronts.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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What does negative camber mean?

Camber is the angle of a tire, when viewed from straight ahead. If the tire stands straight, it is said to have zero camber. If the top of the tire leans toward the center of the vehicle, camber is said to be negative.
For more information on camber and caster, please see our detailed topic Wheel alignment, camber and caster.

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What does SAE 1205-1206 mean with regard to tire valve stems?

SAE stands for Society of Automotive Engineers and 1205-1206 is their standard for ozone resistance in valve stems. These standards are extremely important but not well enforced. Millions of substandard valve stems have entered the US with disastrous results and a huge recall. The results were badly cracked and dry rotted valve stems in use. Unfortunately many tire dealers are ignorant of SAE 1205-1206. Asking if the valve stems being installed meet this standard may be a good way to judge the competence of a tire retailer.

Please see our Detailed Topic Dangerous Valve Stems for more information.
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What does the term separated mean with regard to a tire?

A tire is said to be separated when air leaks between the plies of the tread. This results in a large bulge in the tread and very seriously weakens the tire. Symptoms of a separated tire include a wobble or waddle, especially when rolling at low speeds, under 30 MPH. The condition is very dangerous and complete tire failure very often follows, with little or no warning.

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What does the term speed rating mean in regard to a tire?

The term speed rating arises from the method used to test the structural integrity of tires. This is closely related to the amount of belting the tire has and the loads the tire can withstand, such as cornering and braking. Structural integrity of a tire design is tested by spinning at increasing speed, until centrifugal force tears the tire apart. Different speed ratings are assigned based on this data.

Engineers design vehicle suspensions to load tires during braking, cornering and driving. If the vehicle is engineered for a specific rated tire and a lower rated tire is substituted, handling and safety can be effected. Problems can also appear with irregular wear and vibrations.
For more information on speed ratings, please see our detailed topic, Can I Substitute A Lower Speed Rated Tire.

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What does the term toe mean, with regard to wheel alignment?

Toe is the relationship between the front of two tires, on the same axle, and the rear. For instance, if the distance between the front of the tires on the vehicle is the same as the distance between the rear of the same two tires, toe is said to be zero. If the front of the tires are closer together than the rear, the wheels are toed in.
For more information, please see our Detailed Topic, Wheel Alignment, Toe and Tracking.

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What does the term unibody mean?

A unibody vehicle is one that uses structural components welded together, as a part of the body of the vehicle, rather than having a separate frame assembly. The rocker panels take the place of the frame rails and the front and rear aprons and body structure serve as mounting points for the suspension. By contrast, a frame type vehicle has a separate frame to mount suspension components and the body is supported by the frame. Some unibody vehicle also employ a partial bolt-in sub-frame for suspension mounting.
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What does the term unidirectional tread mean with regards to a tire?

Unidirectional tread has all of the main grooves in the tire facing in a single direction. The theory is, more water can be channeled from under the tire tread, on a wet road. A standard bidirectional tread has grooves facing in both directions. Care must be taken in mounting the unidirectional tire. The treads must face the proper direction in order to work and the direction is normally labeled on the sidewall of the tire.

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What does TPMS mean?

The acronym TPMS stands for tire pressure monitoring system. This is a system that monitors the pressure in the tires of the vehicle and sends a warning when they are out of a specified range. Most systems use wireless sensors located inside the tire. These sensors are often part of the valve stem assembly. There are also systems that monitor wheel speed through the ABS system. Since a low tire is shorter than a fully inflated tire, and rotates faster, wheel speed infers a low tire.

For more information, please see our Detailed Topic Valve caps and TPMS.
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What is a McPherson strut bearing and what symptoms do they normally give when bad?

The strut bearing is the upper pivot point for the strut assembly. This is a small bearing that allows the spring to rotate smoothly when the wheels are turned. Symptoms often include a popping noise when turning or memory steer, a vehicle pull in the direction of the last hard turn.

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What is a steering damper?

A steering damper is basically a shock absorber attached to the steering linkage. The purpose is to help prevent steering wheel shimmy by resisting the quick back and forth movement of the linkage. They are most often used on four-wheel drive vehicles, due to the larger tires presenting more opportunity for wheel shake.
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What is a wheel lock?

A wheel lock is a device, that normally replaces one of the regular lug nuts, on each wheel, and requires a key to remove. They are standard equipment on many vehicles and tend to slow a thief down. A number of tools are available to defeat wheel locks and these inevitably find their way into the hands of thieves; the locks are supposed to keep out. The most important thing is to be aware if the vehicle has them and to keep track of the key.
For more information, please see our Detailed Topic, Wheel Locks.

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What is an out of round tire?

Out of round refers to the tread of the tire not being equidistance from the center point of the wheel opening, when measured around the circumference of the tire. When rotated, out of round causes the tire tread to move up and down.

The affect of an out of round tire is vibration and wear to suspension components. Out of round can be measured with a dial indicator against the tread of a rotating tire. In bad cases, out of round may be seen with the eye. Any amount over .030 of an inch (.762MM) is normally considered excessive.

See our Detailed Topic Out of Round Tires for more information.
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What is four-wheel alignment?

Four-wheel alignment involves reading and adjusting alignment angles at each of the four wheels of the vehicle. Non-adjustable angles are read and compared to specifications. Four wheel alignment allows the front [steering] wheels to be referenced to the rear. Without this reference the front wheels may be aligned to one another but not the centerline of the vehicle.

Not all vehicles are adjustable on all four wheels but the alignment should still be referenced and verified. On vehicles that are adjustable in the rear, rear wheels are adjusted first and then front wheels set in alignment to the rear. When the rear wheels are not adjustable, but are out of specifications, a problem is revealed. Such a problem should be diagnosed and corrected before alignment is attempted.

For even more information on wheel alignment, please see our Detailed Topics article, Wheel Alignment Myths.
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What is meant by match mounting a tire

The concept of match mounting attempts to match the highest point on the tire with the lowest point on the wheel. Some believe this provides a more round assembly and thus a better ride. The procedure is time consuming and can add substantial cost to the price of tire mounting. A far better method is to correct wheels that are not straight and verify that tires are perfectly round before mounting.
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What is the best tire air pressure gauge?

Most gauges tested are not very accurate or worse do not repeat their reading consistently. The pencil or barrel type gauges seem to read better than the dial type, in my testing. The best gauge I have ever tested was the PCL Accura I digital gauge. Very simple to use, rugged and very accurate. We use them exclusively in our shop.
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What is the difference between a strut and a shock absorber?

The two terms are often used interchangeably today. Technically both are shock absorbers as they both serve to dampen suspension oscillations on jounce and rebound. Originally, a shock absorber dampened motion, but did not support load. Originally a strut typically supported a spring, served to dampen motion and support weight. Today there are multiple variations on both designs. Some manufacturers refer to one as a strut, another as a shock absorber and vice versa.

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What is the pressure required for a 245/75R16 tire?

Tire pressure is not dictated by the size, rather by the design of the tire. For example, three 245/75R16 tires may each require a different pressure. For tips on setting the best tire pressure, please also see our Detailed Topic How To Set Tire Pressure for a great deal more information.

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What makes some radial tires cause a vehicle to pull to the right or left when driving?

The term for this problem is conicity. Perhaps an oversimplification, but the tire is slightly cone shaped, rather than flat across its tread surface.

As with any cone shaped object, the tire tends to roll in a circle, toward the shorter side. Conicity is normally cause by uneven distribution of belting under the tread. Alignment of the belts in the carcass is critical. If they are shifted, even a tiny amount, the tire tread will not inflate perfectly flat. If one side of the tread inflates slightly higher than the other, effectively a cone is formed, thus the pull.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.

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What symptoms are present with worn tie rods?

Most vehicles have the four tie rods, two inner and two outer on the front and sometimes on the rear. Tie rods connect the steering mechanism of the vehicle to the wheels. They also hold the wheels in position, relative to each other. When tie rods wear, the wear allows the wheels to toe in or toe out. Excess toe in or toe out causes tire wear. There may also be a loose feeling in the steering or a looseness when hitting bumps.

See our Detailed Topic Wheel Balance, Shimmy and Vibration for more information.
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When are tires considered worn too much to use?

Tires with remaining tread depth of 2/32 inch are normally considered legally worn out. Manufacturers normally cast small raised areas in the tread at this height. When the tread wears down and exposes the wear bars the tire should be replaced.

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When I use my truck for towing, the fan hits the fan shroud.

The fan should be in the center of the shroud with the vehicle at idle. If so, engine movement would be the usual reason for the fan striking the shroud. Such movement is normally the result of broken or improperly attached motor mounts. When towing, the engine is loaded and rises up on the mounts. The movement can cause the fan to strike the fan shroud. If the fan is not in the center of the shroud at idle, possible frame damage might be suspected.
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When replacing only two tires on a vehicle, should they be placed on the front or the rear?

With only two new tires, the new tires should be placed on the rear. New tires provide greater traction and the vehicle will be more stable with the greatest traction in the rear. Slippage in the rear of a vehicle, at speed, will produce far more instability than slippage in the front. This is the case regardless of whether the vehicle is front or rear wheel drive. The affect is similar to a fork lift, turning the rear wheels to produce far more movement when steering.
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When rotating tires, is it ok to cross and/or switch sides, or should you only rotate front to back same side? I heard switching sides can lead to belt damage due to opposite rotation.

Switching sides when rotating will not damage a tire. This is a very persistent myth. Some tires are directional, and can not be switched for that reason. These will normally be clearly marked on the sidewall. Directional means the tread pattern is designed to work in a single direction. Most tires are bi-directional and it makes no difference where they are placed.

I normally let the wear pattern dictate the rotation method. For instance, if the tires appear "chopped" or wearing in spots, I cross-rotate. If wear is very even, straight front to rear.

See our Detailed Topic article Tire Rotation for far more details.
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When should the struts on my vehicle be replaced?

There are several ways in which a strut may fail or need replacement. Most common is leakage. A small film of oil around the shaft is normally not a problem. Fluid covering several inches of the strut or dripping off indicates a need for replacement.

Noise, particularly on bumps, and coming from the strut is another problem indicating need for replacement. This should be carefully diagnosed, as good struts are replaced quite often due to mis-diagnosis of noise source complaints.

Ride quality is somewhat subjective but excessive bouncing and diving of the suspension is another symptom of worn struts. Finally, struts are sometimes bent from pot holes, striking curbs or other impact to the wheel.

Recommendations for strut replacement without the above symptoms should be viewed with scepticism. Strut replacement falls into a category that I feel is very often over sold.
For more information, please see our Detailed Topic, How Do You Know When You Need Shocks or Struts

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When should tires be replaced?

From a standpoint of wear, when the tread is 2/32 of an inch at the lowest point. Tires may also require replacement much sooner, due to cuts or punctures that cannot be repaired. Separation of the tread and bulges in the sidewall will also require replacement, regardless of tread condition. Out of round tires, can cause a great deal of damage to suspension components and should be replaced for that reason.

Dry rotted or tires with cracks in the tread or sidewalls should be replaced. Also, many experts and vehicle makers state, any tire over six years of age should be replaced, regardless of tread condition. See our Detailed Topic article Old Tires With Good Tread for far more details.
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Where are Michelin tires made?

Michelin builds tires in many parts of the world. About 80% of the tires we receive at AGCO Automotive are made in South Carolina, USA.
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Why are cheap tires out of round?

It does not automatically follow that cheap tires are out of round. I have seen very expensive tires that are out of round as well. Rushed production, the type of mold used, lack of quality in manufacture and many other factors produce out of round tires. From there, even a perfect tire can be ruined by improper mounting. Many of the factors that produce round tires have cost associated with them. This is why quality tires tend to be priced higher than low quality tires. All factors considered, quality inevitably cost less, even though the initial price may be more.
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Why are vehicle manufacturers going to electric power steering?

Electric steering has fewer parts, cost less to manufacture and uses less engine power. This offers a small savings in fuel mileage and allows the computer to control steering. Computer control of steering opens the way for features such as self parking vehicles. With electric vehicles it also allows for power steering without having to run a hydraulic system. On the down side, electric steering is more fragile than hydraulic power steering and may be more costly to diagnose and repair.
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Why do some cars use air suspension?

Air suspension improves ride, handling and control of wheel alignment by keeping the vehicle more level. It is generally used on high-end vehicles due to cost.
For more information please see our Detailed Topic Ford Air Suspension Problems.

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Why do some race cars fill their tires with nitrogen?

Race cars are extremely concerned with tire pressure and not overly concerned with cost. One PSI may be considered significant in the handling of some of these vehicles. Nitrogen expands slightly less than air when heated. Since race car tires tend to build and loose heat very rapidly, it is hoped nitrogen will give slightly more consistent readings.

For more information, please see our Detailed Topic Filling Tires With Nitrogen.
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Why do the balance weights keep coming off of my wheels?

Wheel weights come in a wide variety of shapes and clip styles. When weights come off, chances are the improper weight was used for the application.
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Why do “V” rated tires cost more than “H” rated?

To achieve a V rating, the tire requires more belting and higher quality construction than for an H rating.
For more information on speed ratings, please see our detailed topic, Can I Substitute A Lower Speed Rated Tire.

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Why is there an electrical connection on my power steering hose?

Over the years manufacturers have used several types of switches and sensors on the steering. In earlier vehicles, the air conditioner compressor was disabled at full turn. This cut drag on the engine. Later vehicles sometimes use a steering sensor to increase idle speed when steering. Still others have variable power steering. This provides additional boost at low speeds to ease steering and less boost at higher speeds to increase steering feel.
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Why would a tire that has no nails or punctures keep losing air pressure?

Tires can leak in several places. Valve stems are one common place, particularly if the stem cap is missing. Another area of leakage is corrosion around the tire bead area of the wheel. This can leak a small amount in several places and be difficult to find. Leakage that occurs in new tires can be caused by a defect in the tire. Not common, but some tires leak through the rubber sidewalls. This is a defect and such a tire will often be replaced at no cost. Finally, wheels can sometimes have porosity and cause a leak. This is normally diagnosed by switching the tire to another wheel to see if the leak stays with the tire or moves with the wheel.
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Why would my car still squeak after having it greased?

Squeaking in a modern vehicle is normally a sign of a part failure. Bushings deteriorate, ball joints and tie rods wear in time. Properly greasing vehicles that can be greased can help prevent wear. Greasing a worn part is simply too little, too late.
Please see our Detailed Topic All About Ball Joints for more information.

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Why would my vehicle suddenly go out of alignment and start pulling hard to the right?

Vehicles do not go out of alignment. All adjustments lock into place and in order for wheel alignment to change, something must bend, wear out or move. If the adjustments were not properly tightened during the last wheel alignment, something could have slipped out of place. Another possibility would be a tire has separated, which will cause a hard pull, even though the alignment is still okay. Moving the position of the tires, such as rotating, can reveal a tire causing a pull. Conicity, which is a defect in a tire will cause a pull to the right or left when driving and is often mistaken for a wheel alignment problem.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.

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Why would putting shorter tires on my car make my speedometer read faster than I am actually going?

Speedometers calculate vehicle speed based on drive axle speed and the circumference of the specified tire size. For each revolution of the axle it is assumed the vehicle travels a set distance. With a shorter tire the distance is less, so the speedometer will indicate a speed greater than actually traveled.
To better see the effect, use the Tire Size Error Calculator. Enter the original tire size specified for the vehicle and another size being considered. The calculator will give the error of the speedometer in MPH between the two tires.

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Why would the clunk noise in my Sierra Truck steering wheel keep coming back even though the intermediate steering shaft is well lubricated?

Lubrication of the shaft is only part of the challenge. Because of the design, lubricant can actually attract grime which only causes more binding. This often wears the lower steering column bushing and the noise keeps returning. GM has released an updated shaft. Replacement of the shaft and replacement of the lower bushing offers a more long term fix.
For more information please see our detailed topic GM Steering Column Clunk.

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Why would the lug studs on my car continue to break? I know they were properly tightened to the specified torque.

Lug breakage can often be traced to the wrong wheel or lug nut being used. The bolt pattern of many wheels are very close, but not the same. When the lugs are tightened, the studs will bend and eventually may break. Also using the improper nut for the type wheel will cause improper seating and breakage. Finally, if the center hole in the wheel is too small for the hub, the wheel will not seat properly and the studs may break.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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Why would the lug studs on my car continue to break? I know they were properly tightened to the specified torque.

Lug breakage can often be traced to the wrong wheel or lug nut being used. The bolt pattern of many wheels are very close, but not the same. When the lugs are tightened, the studs will bend and eventually may break. Also using the improper nut for the type wheel used will cause improper seating and breakage. If the center hole in the wheel is too small for the hub, the wheel will not seat properly and the studs may break. Finally, worn lug nuts may appear to tighten, but actually bottom out against the base of the stud. This will not hold the wheel tight and can cause the stud to fracture.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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Will power steering fluid work in a vehicle that specifies automatic transmission fluid in the steering?

Both fluids are similar in makeup, but have differences. Automatic transmission fluid or ATF has more detergents and may have friction modifiers, not present in power steering fluid. The viscosity is also different as well as other properties. There are no benefits and maybe problems interchanging the two.

It is also important to note; ATF is not one thing. There are several types of ATF, and the proper type must be used. For example, there is Dexron III, Mercon V, Mercon SP, Toyota T-IV, Honda and many others. Always use only the fluid recommended and only the proper type.

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Will putting load range E tires on my truck decrease my fuel milage compared with load C tires.

If the vehicle specifies load E (10 ply tires) and they are kept properly inflated there should be no loss of fuel mileage. An under rated tire would more likely drop fuel mileage, because the load would effectively make it like an under-inflated tire. If load E tires are used and improperly inflated, there could be a loss of mileage, as with any under-inflated tire.
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Will you explain tire dimensions?

The P-metric system is the most common dimension rating. An example might be P265/70R17 91H. The P at the beginning means this is a passenger tire. The 265 is the width in millimeters, at the widest point of the tire. Slash 70 is the aspect ratio, which means the tire is 70% as tall as it is wide. The R indicates radial construction and 17 is the diameter, in inches, of the wheel. There are normally numbers and a letter following this. The number 91 above is the load rating for the tire and the H is the speed rating.

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For more information, please see our Detailed Topic, Can I Substitute A Lower Speed Rated Tire.

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With no grease fittings on my vehicle, what can I do to prevent expensive suspension problems?

By eliminating the grease fittings manufacturers actually extended the life of suspension parts greatly. Improper lubrication and contaminated lubricants contributed more to wear and tear than lack of lubrication. That said, proper lubrication (very rare) would have greatly extended the life, but that's another story. By a very wide margin, the single largest factor in suspension life is buying a quality round tire and having them mounted and balanced by a trained professional. This step alone can literally save thousands in repair over the life of the vehicle. The consequences of cheap tires, improperly mounted and balanced are far too expensive.

See our Detailed Topic Ruining New Tires for more information.
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Would a tire store be liable for an accident if they installed lower rated tires than recommended on my vehicle, and they fail?

Only a court of law may decided liability, based on the circumstances. Improperly rated tires may change the handling and braking characteristics of a vehicle. This seems to me, a great risk for a tire store to assume, even with client insistence.
For more information on speed ratings, please see our detailed topic, Can I Substitute A Lower Speed Rated Tire.

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Would rotating my tires cause my car to pull to the right when driving?

Rotating tires cannot cause the vehicle to pull, but can reveal a problem that causes a pull. For instance if the two rear tires have different tread patterns, different wear or one rear tire has ride disturbance, the vehicle may start to pull. Air pressure could be another concern if one rear tire was low. Different tire sizes can also cause a pull and will be less noticeable on the rear. The rotation did not cause the problem. Rotating the tires simply revealed a problem that was being masked by the tires being on the rear.
For more information on how a tire can cause a vehicle to pull right or left, please see our Detailed Topic Tire Conicity and Radial Pull.

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Brakes, ABS & Traction Control

A brake caliper seized on my vehicle. I replaced it and a few month later it happened again.

A very contaminated system can cause repeated hydraulic failure. Therefore, brake fluid should always be thoroughly flushed, BEFORE any components are replaced. Pushing contaminated brake fluid through new parts, as when bleeding, almost insures repeated failure. Brake hoses can also produce debris that can lodge in a caliper and cause it to fail. I normally recommend brake hoses whenever calipers are replaced.

See our Detailed Topic article Brake Hoses Can Bury You for far more details on brake hoses.
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A friend told me I should always replace the rear brake springs and hardware when I replace the rear brake shoes. What do you recommend?

On high mileage vehicles replacing the rear springs is not a bad idea. They do wear out and loose tension over time. There are also times when brake shoes are replaced at lower mileage, for instance under 75,000. On these vehicles springs are inspected, but if carefully removed, can be reused.
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ABS Light comes on as soon as the car moves forward. The self-check passes - (i.e., the light comes on when the ignition switch is turned on and it clears after engine starts)

The ABS system runs a rudimentary series of test when the key is turned on. Primarily this is checking for electrical continuity or open circuits. For instance, if a sensor were unplugged. When the vehicle starts to move it does another series of checks, applying "fuzzy logic." For instance it may compare the speed of the wheels and if one reads too far out of range of the other three it may check for brake application. If the brakes are not applied the system infers a problem exists and turns on the light.

Another test may be how long the pump takes to build a certain level of pressure or how long the pressure holds before dropping a preset amount. When the light illuminates, there is a malfunction in the anti lock brake system. Cycling the ignition clears the current problem so the light goes out until the test is run and failed on the next key cycle.

Delaying repair may increase cost, as some simple problems can become more involved if left unattended.
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After driving a short distance the front brakes on my vehicle lock up. After it sits, it will again drive but then happens again. I changed the front calipers but it still occurs.

A likely cause is the return port in the brake master cylinder being blocked. If the master cylinder piston is too far forward in the bore, the seal-cup will cover the port. When this small hole is blocked, fluid cannot return to the master cylinder when the brakes are released. As the fluid heats, expansion applies the brakes.

Diagnosis is easy. Drive the vehicle until the brakes lock and then loosen the steel line at the master cylinder. This allows the pressure to escape. If the brakes immediately release, a blocked port is a likely cause. This may mean a bad brake master cylinder or simply the push rod that moves the master cylinder out of adjustment. A bad brake booster can also allow the push rod to travel too far and cause similar symptoms.

Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.

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After replacing my front brake pads, the brake pedal is now very low.
There could be several causes for a low pedal after brake pad replacement. If no other components were replaced, check these suggestions:
- Non-original brake pads often do not produce the same friction as the originals. This requires more effort to stop and thus a lower pedal.
- A rough (greater than 30 micro-inch) finish on brake rotors will require greater brake pedal effort and lower the pedal.
- Contamination on the brake rotor or pads, such as greasy finger marks can increase pedal effort.
- Air may enter the system when the caliper pistons are retracted. Air compresses and increases pedal travel.
- If the vehicle has adjustable wheel bearings, a loose bearing adjustment can cause rotor movement, pushing the caliper pistons in and increased pedal travel
- A caliper piston sticking in its bore after being pushed in. This is particularly common on phenolic and double piston calipers.
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After replacing the brake shoes on my vehicle the wheel cylinders started to leak and ruined the new shoes. They were not leaking before I replaced the shoes, what’s going on?

The pistons in wheel cylinders only travel a small distance when used. As the shoes slowly wear the area that they travel moves farther from the center of the cylinder. The area in the center of the cylinder is now no longer in contact with the seals. Over time this area tends to corrode from this lack of use.

When new shoes are installed they are much thicker than the worn out shoes and the pistons and seals are once again returned to their original positions. The seals are now operating in a corroded portion of the bore and often start to leak. We find it more cost effective to replace cylinders when shoes are replaced.
Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.

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After replacing the brakes on my vehicle I have an annoying squeal whenever they are applied.

Brake squeal is a vibration between the pad and the brake rotor. It has many causes, most relating to improper brake material or installation. We have found after-market (not the vehicle manufacturer’s) brake pads to be a common source of brake squeal. We have had excellent results by replacing pads with OEM (original equipment manufacturer) pads.

Many vehicles also employ metal shims between the pad and the brake caliper. These shims help dampen the vibration that causes noise. Sometimes when brakes or improperly serviced these shims are discarded or improperly installed. There are also several pieces of hardware that holds the brake pads firmly in the calipers. These can be damaged or even left out in an improper service.

Rotor finish may also affect brake noise. For proper braking the surface finish should be 60 micro inches or better. A rougher finish can greatly increase vibration. Lastly, failure to clean the rotor surfaces, caliper mounts and slides, or improper lubrication of these parts can cause noise concerns.

For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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Are there any test I can perform to test a vacuum brake booster?
There are three simple test that can give you a reasonable idea. Of course the source of vacuum should be tested and verified before condemning a vacuum brake booster.
1. Pump the brake pedal several times, without the engine running. This will exhaust the vacuum reserve in the chamber. Depress the brake pedal and start the engine. As vacuum charges the chamber, the pedal should drop slightly. This verifies the booster is working and receiving vacuum.
2. Run the engine to charge the vacuum chamber. With the engine off, slowly push and release the pedal, four times, about once every 5 seconds. On each stroke the pedal should rise slightly. This shows the release valve is operating.
3. Run the engine for one minute. With the engine off, hold normal pressure on the pedal for thirty seconds. The pedal should not rise in this time. This test shows if the booster holds vacuum.
Other test might include listening for noise when the pedal is pressed and checking for full and smooth return of the pedal when released.

For more information, please see our Detailed Topic Vacuum Brake Boosters.
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Can a leaking brake master cylinder cause the power brake booster to fail?

Brake fluid leaking into the booster is one of the leading causes of vacuum brake booster failure. Fluid can leak past the rear seal in the master cylinder and enter the booster. Brake fluid will cause rapid deterioration of the booster diaphragm. Ironically, replacing the brake master cylinder will almost guaranty a repeat failure. Once the diaphragm is damaged, vacuum leaking from the booster can quickly destroy the replacement master cylinder.

For more information, please see our Detailed Topic Vacuum Brake Boosters.
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Can a warped rotor be corrected by turning?

My thought is that if a rotor warps at full thickness, it is more likely to warp again when machined thinner. I have found it more cost effective to replace warped rotors. Turning warped rotors rarely provides lasting results.

It is important to remember that a warped rotor is normally a symptom of another problem. Simply replacing the rotor will many times result in the rotor warping again, if the root problem is not diagnosed and corrected.

For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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Can brake rotors be damaged by improperly installing the wheels on a vehicle?

Too much torque or improperly tightening of the lug studs can damage the wheel hub. Brake rotors often are attached to or are a part of the wheel hub. This can cause run out in the rotor which can cause it to warp and produce brake shudder.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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Can DOT 4 and DOT 3 brake fluids be mixed?

DOT 3 and 4 are both alcohol based fluids and are compatible with each other. DOT 4 has a higher initial boil point than DOT 3, when both are fresh and uncontaminated. Adding DOT 3 to DOT 4 will lower the boil point and should never be done on a system that specifies DOT 4.

Because of the agents that give DOT 4 a higher boil point, it is also more susceptible to contamination. Moisture can enter the fluid and lower the boil point significantly. DOT 4 can be substituted for DOT 3, but should be replaced more frequently than DOT 3.
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Can flushing my brakes cause any harm?
Properly done, brake fluid replacement will never harm a brake system. Like any other service, it can also cause harm if rendered improperly. Leading problem causes include:
- Using contaminated brake fluid. Fluid from a container that has been opened may induce more moisture into the system than is being removed.
- Allowing dirt to enter the system. Hydraulics should be kept as near sterile as possible. Poor service procedures can introduce debris.
- Introducing air into the system. By using poor methods or an improper bleeding sequence, air may enter the system.
- Over-stroking the master cylinder. An older master cylinder can be ruined by pushing the pedal to the floor, as in improper brake bleeding. Corrosion may occur beyond the area of normal piston travel. Pushing the piston beyond this point can ruin the seal. Proper bleeding always limits pedal stroke to the normal area of travel.
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Can over-tightening wheel lugs cause brake rotors to warp?

Too much or uneven lug torque are a factor in warping brake rotors. There is a specified amount of torque, given by the vehicle manufacturer and a preferred pattern for tightening the lugs. The actual torque depends on the diameter, thread pitch and material of the studs.

For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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Can power steering fluid be flushed from a brake system if accidentally added?

Brake fluid is generally an alcohol based product. Power steering fluid (petroleum) is rapidly and selectively absorbed by the rubber in the brake system. This causes the rubber to swell and soften rapidly and compromises the hydraulic system. There is no way to flush or clean the petroleum from the rubber.

Attempting to flush the brakes, once contaminated, will normally only distribute the contaminant more fully throughout the system. If this occurs, the only safe repair is to replace any rubber that has been contaminated, which is generally all rubber in the system.

If caught immediately, before any power steering fluid has entered the system, replacing the master cylinder and reverse flushing the system is often effective.
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Can water cause brake rotors to warp?

Driving a vehicle through high water when the rotors are hot is one cause of rotors becoming warped. For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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Does brake fluid go bad?

Both DOT 3 and DOT 4 brake fluid are alcohol based. Alcohol is hygroscopic and absorbs moisture over time. This will occur much faster in an opened container, but also occurs in a sealed container. Moisture lowers the boiling point of the fluid and contributes to corrosion. Once brake fluid is opened, it should be used and the remainder properly disposed of. It is also best not to use sealed containers, after they have reached several years of age.
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Does it matter what type of brake fluid I use in my vehicle?

Virtually all common modern production vehicles use either DOT 3 or Dot 4 fluid. Both are alcohol based and are compatible with each other. DOT 3 has a lower boiling point than DOT 4, but does not saturate as fast with moisture. You should always follow manufacturer’s guidelines and use the proper fluid.

It is also important to use only brake fluid from a new and unopened container. Being made of alcohol, brake fluid quickly absorbs moisture when exposed to the air. Even in a tightly resealed container fluid will be contaminated in a short period of time. Using contaminated fluid can cause severe damage to the system. Always use a freshly opened container and properly dispose of any remaining after use.
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How can I tell if I have bad brake calipers?
Brake calipers, like many parts, fail in several ways. The symptoms generally depend on the nature and severity of the failure.

Some possible symptoms of bad brake calipers include:
- Leaking brake fluid, from the caliper area
- A pull to the right or left on braking
- Rapid brake pad wear and uneven brake pad wear
- Brake rotors that continue to warp
- A wheel that is difficult to rotate
- Heat or smoke coming from the brake with the bad caliper
- A bad shaking in the steering or a feeling the brakes are still applied when driving
It is also important to realize, most of these systems can also be caused by other components as well. For instance a pull on braking can also be caused by worn suspension parts, a bad brake hose, brake rotors as well as other things. A professional hydraulic test is sometimes the only way to isolate a bad caliper as the cause of the problem.

For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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How do I reset the brake fluid level light on my Camry?

The brake fluid level light should reset when fluid is added to the proper level. If the light does not go out, the level sensor may be bad. A quick test is to unplug the sensor and see if the light goes out. If not, remember many times the same light is used as the parking brake indicator and sometimes to monitor the brake system for hydraulic failure. If the light remains on, check for faults in these areas.
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How do you bleed brakes?

There are several methods, depending on the design of the system. Pressure is applied to the brake fluid and a threaded opening, called a bleeder screw is opened until air escapes. When pure fluid runs out, the bleeder is closed and this is repeated at each bleeder port.

Methods vary greatly for applying pressure to the system and the order in which the ports are bled. The order is known as bleeding sequence and varies considerably from model to model. On older vehicles bleeding normally started at the wheel furthest from the brake master cylinder. With modern brakes there are several patterns. Using the wrong sequence can result in even more air being drawn into the system.

Older systems also normally recommended pumping the brake pedal to produce pressure in the system. This will no longer work with many systems and can cause damage to the master cylinder. Instead, combinations of pressure tanks, vacuum and reverse pressure are often used. Many newer systems must have a factory scan tool to run the ABS pump to bleed air from the system.
Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.

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How does an ABS braking system work?

Design varies from one vehicle to another. There are sensors that read the speed of the wheels. This information is fed back to a computer that compares each wheel to the others. When a wheel slows to a predetermined percentage below the others, it is inferred to be locked up. At this point a valve closes to block pressure from reaching that wheel and another valve opens to relieve the pressure on the line to the wheel.

Once pressure is released from the wheel, its speed increases. When it equals the other wheels, the system releases the pressure and continues to monitor the speeds. This occurs many times per second and switches among the wheels as needed. Certainly this is a vast over-simplification but is the basic concept.
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How long do brake pads last?

The answer will vary, depending on the ratio of highway to city miles, the way the vehicle is driven and the type of vehicle. Miles are not a good indicator of brake wear. A vehicle driven primarily on the highway can travel a great many miles with very few stops. Stopping wears brakes, not miles driven.

Hard braking also decreases life significantly. Regularly allowing the vehicle to decelerate and coasting to a stop can more than triple brake life. Repeated hard stops build heat and vastly reduces brake life. The type of vehicle also has an affect. For instance, the brakes on some vehicles are designed to last longer than on others.

As a general rule, brakes should be checked at around 15,000 miles and replaced before 90% of the material is worn away, normally about .060 inch remaining on the thinnest pad. On many vehicles this occurs around 30,000 to 45,000 miles, but can vary significantly based on above mentioned conditions.
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How much does it cost to flush brake fluid?

Every shop uses their own methods of billing so prices vary. The procedures and thoroughness of the process also affect cost as well as the type vehicle being serviced. Proper flushing of brakes normally takes around forty-five minutes on most vehicles. There will also normally be a charge for the fluid used and disposal of the old fluid. With shops that charge for actual time spent, you might figure the shops service rate per hour, times .75 (forty-five minutes) plus a small amount for fluid and disposal for an approximate figure.
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How much vacuum does a brake booster have?

Brake booster vacuum should equal intake manifold vacuum, about 14 to 20 inches of mercury.
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How often should brake rotors be replaced?

There is no specific time-frame for brake rotors, rather replacement is based on condition. When the surface finish is worn excessively, very rough or if the rotor is warped, it needs to be replaced. Several factors influence rotor life. Some vehicles wear rotors very quickly, due to design. This is particularly prevalent on European vehicles. Aftermarket brake pads can also contribute to rotor wear. A problem in the system, such as a binding caliper or stuck caliper slide will quickly ruin rotors. Driving style also has a great influence on rotor life. Hard braking, stopping very quickly and riding the brakes can ruin rotors.

For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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How often should I change my brakes?

The answer will vary, depending on the ratio of highway to city miles, the way the vehicle is driven and the type of vehicle. Miles are not a good indicator of brake wear. A vehicle driven primarily on the highway can travel a great many miles with very few stops. Stopping wears brakes, not miles driven.

Hard braking also decreases life significantly. Regularly allowing the vehicle to decelerate and coasting to a stop can more than triple brake life. Repeated hard stops build heat and vastly reduces brake life. The type of vehicle also has an affect. For instance, the brakes on some vehicles are designed to last longer than on others.

As a general rule, brakes should be checked at around 15,000 miles and replaced before 90% of the material is worn away, normally about .060 inch remaining on the thinnest pad. On many vehicles this occurs around 30,000 to 45,000 miles, but can vary significantly based on above mentioned conditions.
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How tight should I adjust front wheel bearings on a Ford Pick Up?

Adjustable roller bearings should not be tightened. The bearings should be set to provide the proper end play. This is best done with a dial indicator, attached to the brake rotor and measuring end play with the spindle. Grasp the rotor at three and nine O’clock and with firm pressure, push in and out. The end play should be between .004" and .006 inch. Less clearance can cause the bearings to burn up when they expand in operation. Too much clearance will cause accelerated wear and slop in the steering.

With non-adjustable bearings the end play is manufactured into the bearing. The inner races are designed to contact before the end play is taken up. If torque on the retainer is proper the end play on the bearing will be within specifications.

See our Detailed Topic article Adjusting Wheel Bearings for far more details.
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I accidentally poked a hole in the piston boot on the back brake caliper while replacing the pads. How do I fix it?

The piston boot is available as part of a caliper-rebuild kit. These are available at most part stores or a dealership part department. The boot presses into the piston bore with light pressure. It is not difficult to replace nor expensive to purchase. Best is to replace it immediately. Debris and moisture that enters the caliper, through the torn boot, will cause failure.
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I am having a great deal of trouble trying to bleed the brakes on my vehicle. They seem to still have air in the lines.

No longer will the time honored sequence of right rear, left rear, right front, left front suffice. Many vehicles now use a very different sequence and procedure. For instance some may start with the left front then the right rear, etc. Check a service manual for the vehicle you are working on for the proper sequence.

If the proper sequence is being followed, the procedure could be the problem. It is normally wise to wait up to 15 seconds between single pedal strokes when pedal bleeding a system. This allows any trapped air to rise and escape through the reservoir.

Sometimes allowing the vehicle to sit for several minutes with each bleeder screw open, one at a time can help. Gravity will cause the fluid to drip and also sometimes helps remove the air. We use gravity bleeding, vacuum bleeding, pressure bleeding and pedal bleeding in the shop. Often one method gives better results than the others.

It is also necessary on some vehicles to activate the ABS system with a scan tool to bleed totally the system. If none of these methods work, likely air is being drawn back into the system. Stuck caliper slides or bad seals can cause this problem. I have seen seals leak air into the system but not leak fluid when pressurized.
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I am restoring an older vehicle and was wondering if the stainless steel flexible hoses are worth the price?

Stainless steel braided hoses are primarily for appearance. They can also provide a small amount of abrasion resistance in off-road applications. Under the attractive stainless steel cover is a conventional type hose. With ordinary use, the standard rubber hose is fine and a lot less expensive.
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I had a bad shudder on braking and replaced my front rotors. The shake is much better but still there.

The new rotors should be checked, for being true and the faces for being parallel. New does not equal known-good and you could have a bad part. If the new rotors are true and the faces are parallel, check the hubs over which they mount. Hubs are sometimes bent and corrosion can keep the rotors from seating properly.

Rear rotors with excessive run-out or parallelism problems may also cause a steering wheel to shake. If all rotors and hubs are tested and known good, I would suspect a loose suspension component. Sometimes loose parts will cause vibration when loaded by the brakes.

For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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I have a Honda and recently had a front brake job done. Now when the vehicle is sitting in drive with my foot on the brake, the pedal will slowly sink to the floor. Do you think the brake job was done improperly?

The two most common reasons for the brake pedal to sink are a leak in the hydraulic system or a master cylinder bypassing internally. A low brake reservoir is a tell-tale sign of a leak. This requires a full inspection of the hydraulic system to determine the source.

If the fluid level is still full, it is more likely the master cylinder is bypassing internally. The cylinder is divided into two parts. When bypassing, fluid leaks from one part to the other. This normally does not result in a loss of fluid.

Either situation can be dangerous and the vehicle should be towed to the shop of your choice for repair. If the master cylinder is the fault I recommend only using a new cylinder. My experience has been very poor with rebuilt master cylinders.
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I have been told I should replace the brake fluid in my vehicle. Why should I consider this?

Both DOT 3 and DOT 4 brake fluid are made of alcohol. Alcohol is hygroscopic by nature and quickly absorbs moisture that enters the system. This effectively helps control the moisture, to a point. The problems are, as the fluid absorbs moisture, the boiling point is lowered and moisture becomes corrosive over time.

The only way to remove the moisture from the system is to replace the fluid. This helps to prevent corrosion from damaging expensive components, such as ABS brake controllers. It can also help prevent pedal fade which can result from brake fluid boiling at high operating temperature. We suggest replacing brake fluid every two to three years.
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I have noticed brake calipers that come with brake pads already installed. They seem a lot cheaper than buying pads separately?

These are generally referred to as loaded calipers. In my experience the pads supplied are not high quality and have not been lubricated. I only install original equipment brake pads. This has given excellent results for many years and allowed me to solve a great many brake problems for clients. For best results I recommend purchasing unloaded calipers and buying original equipment brake pads separately. It is always less expensive to do the job right the first time.
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I recently had a front brake job on my vehicle, and now it takes a lot more pressure on the pedal to stop. The pads were replaced and the rotors turned.

Many things cause high pedal effort. If the effort was good prior to the brakes being worked on, there are two likely causes. Brake pads that are not of original equipment manufacturer’s (OEM) quality or too rough a finish on the brake rotors. Aftermarket pads sometimes lack the proper coefficient of friction provided by the original pads.

Brake rotor finish is also crucial to braking effort. The finish must be 60 micro inches are better to provide proper results. With a surface-test device the finish can be sampled and this possibility confirmed or eliminated.
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I replaced the brake pads on my vehicle and did not open the hydraulic lines. Now my pedal is low like there is air in the lines. Is this possible?

Air may enter the brake system around caliper and wheel cylinder seals, even though they are not leaking under pressure. The best policy is to flush the system before work is begun and bleed again after replacing the pads. Also use only fluid from a new, not previously opened can.
Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.

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I was told the brake rotors on my vehicle were bad, is there a test to determine this?
The word bad is very general. Rotors can be no longer fit for service for any number of reasons.
- The amount of material remaining on the faces can be too thin. This is checked with a micrometer and there is a published specification.
- The surface finish can be too rough, 60 micro inches is normally considered maximum.
- The faces can be out of parallel. The specification is normally in ten-thousands of an inch.
- The faces can have lateral run-out, normally referred to as warp.
- Excessive corrosion to the faces or structure can make a rotor unusable.
- Cracks in the faces or structure can make a rotor unusable.
- Rotors can also be excessively out of balance, have damaged or mis-drilled lug holes, damaged bearing surfaces, hot spots in the surface and several other flaws.
- In your opinion how often should I replace my brake fluid?
  
  Most brake fluid is made of alcohol and absorbs moisture from the atmosphere. This occurs 24 hours a day and whether the vehicle is driven or not. Time is a better indicator of when to change than miles.
  
  Color is NOT a reliable indicator of moisture content. Some fluids that are clear may be contaminated and others that are dark may be okay. Moisture content will lower the boiling point of the fluid and increase corrosion to the system.
  
  Brake fluid can be tested with a refractometer, to reveal its moisture content. Without such an instrument a good rule of thumb would be every two to three years and before any brake service.
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- Is there a difference in changing the brakes on an ABS equipped vehicle and a non-ABS vehicle?
  
  If proper procedures are used there is very little difference. ABS systems can contain several expensive components, such as hydraulic control modules. Pushing the caliper pistons into their bores, without expelling the fluid, can cause problems. Doing so is bad procedure even on non-ABS vehicles. The debris in the caliper can be forced back through the system. Completely flushing old fluid from the system before beginning is the best practice. At least, the bleeder screw should be opened to expel the old fluid.
  
  If hydraulic components are replaced or if air enters the system, some ABS vehicles can be difficult to bleed and require special equipment.
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- My 2002 GMC Yukon ABS light came on, around the same time I started hearing a buzzing noise. When I turned the truck off the noise continued and will not stop?
  
  The electronic brake control module (EBCM) on the Silverado, Suburban, Yukon, Sierra, etc. often causes this problem when it fails. The silicon controlled rectifier (SCR) that controls the ABS pump fails, directing current to the pump continuously. Temporarily removing the ABS fuse, under the hood will stop the pump until the vehicle can be repaired.
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- My ABS and traction control lights come on, what could be the cause?
  
  ABS and traction control are closely related and use much of the same circuitry [see this section on “How does ABS work,” and “How does traction control work.”] When a fault is encountered in a component shared by both systems, both lights will come on.
  
  There could be dozens of causes, some minor and others more major. To diagnose the problem a scan tool is used to retrieve fault codes from the brake control module (BCM). These codes will indicate a general area that could be causing the problem. For instance it could read left front speed sensor fault. At this point the technician uses other equipment to test the components in that circuit.
  
  A great deal of money is wasted by people who take fault codes literally. In the above example, they may simply replace the sensor, only to find the light is still on. The code indicates only what the computer interprets. The cause could be a loose or broken connection, a bad tone wheel, a defective computer driver circuit, a bad tire or many other things. This is why it is much less expensive to refer such problems to trained professionals with knowledge of the system.
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- My brake pedal has become very hard to press lately. I suspect the vacuum brake booster is going out, is there an easy test?
  
  As a quick test, without the engine running pump the brake pedal several times. Now place your foot on the brake pedal with a firm pressure. Start the engine and the pedal should drop slightly. If not the booster is likely not working, but not necessarily bad. The vacuum source to the booster must also be tested with a vacuum gauge.
  
  The gauge should be connected inline with the booster and should read very near engine vacuum with the pedal applied or released. If not, isolate the source of the vacuum problem before proceeding with the booster check.
  
  For more information, please see our Detailed Topic Vacuum Brake Boosters.
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- My brakes squeal when I apply them, after getting a brake job. Is there a break in period?
  
  Modern brakes do not require breaking in and should not squeal objectionably. Squealing on application is always a result of vibration. The pads vibrate on the rotor surface and the noise is transferred through the calipers and into the vehicle.
  
  Stopping brake squeal starts with doing a proper job. Pads, rotors, calipers and caliper slides must all be clean. The back of the pads must be lubricated with high temperature caliper lube. If the vehicle uses pad shims (most do) they must be present and in good condition. All hardware must be present and installed properly. My experience is also that original equipment brake pads make much less noise and stop better than aftermarket pads.
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- My car has a shimmy or shudder when braking. I have been told the brake rotors are warped. Will replacing the rotors stop the shimmy?
  
  Replacing the rotors will very likely stop the shimmy, for a while. Brake shudder is a symptom of a problem, not the problem itself. Replacing the rotors is treating the symptom, but if the root cause is not addressed the problem will return. The possible causes are numerous and can be involved to diagnose. Some of the more common causes are rotors/drums that have been improperly machined. Caliper slides that are binding, improper brake material being used and rear brakes not functioning properly.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- My GM vehicle recently developed a high pitched squeal whenever it is rolling. The noise stops when I apply the brakes are sit at a stop.
  
  One strong possibility is the warning indicators on the brake pads rubbing on the brake rotors. This is a warning that the brake pads are worn and will soon begin damaging the brake rotors. The brakes should be inspected and the pads replaced immediately to prevent damage.
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- My rear brakes wear out before the front brakes. What could cause this?
  
  As a general rule, front brakes traditionally wore out before the rear. As with any general rule this is sometimes not the case. For instance the GM Silverado series trucks, with four wheel disc brakes. On these vehicles, rear pads tend to wear faster than the front. Several other vehicles do the same. The size of the pad material and the bias of braking also contribute to wear rates.
  
  If the wear is excessive or rapid, binding rear calipers, master cylinder adjustment and ABS control valve problems can all cause rear brake wear. With drum type brakes, a defective self adjustment system or sticking rear wheel cylinders can also cause rapid rear wear.
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- My steering wheel sometimes shakes in my hands when I apply the brakes. This started about two months after I replaced my front brake pads.
  
  If the shake or shudder is only when you brake, a common cause is warped brake rotors and/or drums. This feels similar to “shimmy” except that it stops when you release the brakes.
  
  To correct shudder caused by rotors and brake drums it is important to remember the warped parts are a symptom and not the root cause of the problem. Merely replacing the rotors/drums will normally only offer temporary relief from the symptom, and it will often return.
  
  The possible causes are numerous and can be involved to diagnose. Some of the more common causes are rotors/drums that have been improperly machined. Caliper slides that are binding, improper brake material being used and rear brakes not functioning properly.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- My vehicle has 40,000 miles and the brakes have never been replaced. Is there an indicator that will let me know when they need replacing?
  
  Some vehicles have no indication at all while others have warning lights or an audible warning. It is always wise to inspect your brakes at around 15,000 miles and then once a year thereafter.
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- My vehicle has a shudder on braking and I am told the brake rotors are the cause. The brake pads are still good, is it okay to just replace the rotors?
  
  Brake pads and rotors work together and should always be replaced together. The exception being the brake pads can be replaced without rotors if the rotors are still serviceable.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- My vehicle is equipped with an anti-lock braking system but it does not seem to stop any faster than my older vehicle without ABS. Should I have the system checked?
  
  Anti-lock braking systems (ABS) are not designed to make a vehicle stop faster. Their function is to prevent wheel lockup during braking. This helps the driver maintain control of the vehicle as rolling wheels are easier to control than sliding wheels.
  
  The system is designed to test itself when the vehicle is started and at preset intervals when driving. If a malfunction is encountered the ABS light will illuminate.
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- My vehicle pulls to the right when I apply the brake and stops when they are released. I have replaced the brake calipers, rotors, pads and had the suspension completely checked and the wheel alignment set, any ideas?
  
  A very common cause of brake pull is a bad brake hose. Internal failure can cause the hose to act as a valve, blocking brake pressure. Ironically, the vehicle will pull toward the good brake hose as that wheel is trying to stop and the other is not.
  
  See our Detailed Topic article Brake Hoses Can Bury You for far more details on brake hoses.
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- On hard application my rear brakes sometimes lock up?
  
  Rear brake lock up can result from contamination on brake shoes. Most often this comes from a leaking wheel cylinder or a leaking axle seal. Other causes include, a rear wheel cylinder that binds, loose brake components and worn backing plates.
  For more information on drum brakes, please see our Detailed Topic, Solving Drum Brake Problems.
  
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- One brake rotor on my vehicle was damaged by a bad brake caliper. The mechanic wants to replace both front rotors and said damage can occur if not.
  
  Sometimes, when a new rotor is used with an older brake rotor, the vehicle will pull when the brakes are applied. Unfortunately, this may not be learned until the vehicle is fully assembled and driven. At that point the cost is much more to disassemble the vehicle and replace the other rotor.
  
  Beyond a pull on braking I see no damage being done, if the existing rotor is in serviceable condition. You might check the price both ways and then weigh the risk. If you inform the shop, you are willing to assume the risk, they may be more willing to try.
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- Power steering fluid was accidentally added to my brake fluid reservoir. Soon after, the brake warning light came on.
  
  Rubber seals used in brake systems are designed to work with alcohol based fluid. Petroleum based fluid, like power steering fluid, will quickly destroy the rubber parts of the system. Since failure of almost any seal in the brake system is critical, replacing every rubber component in the system is the normal repair. It is also necessary to clean thoroughly all other components such as the steel lines. Any traces of remaining contaminants may cause future problems.
  Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.
  
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- The first brakes on my Toyota lasted 40,000 miles. I had them replaced 15,000 miles ago and now the left front is metal on metal on the outboard pad, and has ruined the rotor. The shop says it must have been a bad set of pads and suggest new
  
  You are wise to be suspicious. Replacing only the pads and rotors seems like treating the symptom only. Each brake caliper on your vehicle has one piston and two pads. This means the piston applies the inboard pad and the outboard pad is applied by the caliper bracket moving on the caliper slides. If these slides are not free to move they will apply the outboard pad, but not release it. This will cause very rapid wear to the outboard pad.
  
  The caliper slides should be inspected and serviced or replaced as needed. Improperly serviced caliper slides are a source of a great many problems. Proper service of the caliper slides should be part of every brake service.
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- The front brakes on my vehicle are getting thin and I plan to replace the pads myself. Do you recommend turning the brake rotors?
  
  I only recommend turning rotors under very few conditions. If the vehicle stops smoothly and with no vibration or shudder, the rotors should be inspected. If the thickness measures within specifications and the surface has no groove beyond .050 inch deep the rotors can be reused. The surface should be thoroughly scrubbed with hot soapy water before use.
  
  If the rotors are worn below specifications they should be replaced and not reused. If the rotors are warped, it has been my experience that it is also best to replace them.
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- The front wheel bearings in my truck needed to be replaced. The shop recommended that I also replace my front brake pads, even though they were not worn out. Is this a good idea?
  
  It could be, you need more information. Brake pads might be suggested for several reasons, other than just wear. When the front bearings are removed the brake pads are very accessible. If they are getting thin, even though not worn out, it may be far less expensive to replace them now.
  
  Weighing the remaining amount of brake against the cost savings might give you a better idea. For instance, check the cost to replace them now as opposed to replacing them later. The saving could then be compared with the remaining life expected from the present brakes. It should also be asked if there is another reason they are being recommended. For instance, has grease from the bearing seal gotten on the pads or are the pads otherwise damaged.
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- The rear axle seal leaked oil onto my brake shoes. The shoes are good other than that can they be cleaned?
  
  Brake shoes cannot be cleaned of oil. The oil permeates the material and will continue to secrete out when the shoe reaches temperature. Any cleaner that might be used can also break down the brake material, causing them to deteriorate. The shoes should be replaced and the drums very thoroughly cleaned to remove all traces of oil.
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- There is a deep scratch in one of my front brake rotors. What should I check for? Does this indicate a bad brake caliper?
  
  I would check to see if the brake pad wear is even from side to side and inboard to outboard. If wear is even and there is no signs of overheating (blue color to the rotor,) a brake caliper is not likely. You can also check the force required to rotate both front wheels. A sticking brake caliper will usually produce a noticeable drag in the rotating wheel.
  
  Scratches sometimes result from debris trapped between the pad and brake rotor. With no other symptom, I would not be overly alarmed by the scratch alone.
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- What are the symptoms of a bad brake caliper?
  
  The symptoms can vary greatly, depending on the type failure experienced. For instance, some calipers may leak, but cause no additional problem. The only symptom might be a low fluid level. Another may seize in the open position. This will often result in a pull on braking, ironically in the direction of the working caliper.
  
  It is also possible for calipers to seize in the closed position. This normally results in overheating the rotor. Symptoms can be a burning smell, smoke, vibration, noise and a good deal of dusting. In less severe cases, there are often no noticeable symptoms when driving. In these cases an inspection of the brakes will sometimes show a brake pad worn significantly more than the others. Sticking calipers also often result in warped rotors, and shudder when braking.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- What are the symptoms of a bad brake hose?
  
  Brake hoses can fail in a number of ways. They can leak or rupture, this causes the brake pedal to fall drastically and diminishes braking. They can break down internally and cause a pull to one side or the other on brake application. One of the most common symptoms and one that is often overlooked is a bad brake caliper. Debris from failing brake hoses is a leading cause of brake caliper failure, in our experience.
  
  For more information on brake hoses, see our Detailed Topic Brake Hoses Can Bury You.
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- What are the symptoms of a bad vacuum brake booster?
  There are at least four primary symptoms and they may occur in combination.
  1. The brake pedal may be harder than normal to depress.
  2. There may be a noise, often a hissing or squeak when the brake pedal is depressed.
  3. The brake pedal may not return to the proper height when released.
  4. The brake pedal may kick-back are jerk when pressed.
  Always test for a proper source of vacuum and rule out conventional brake problems before condemning the brake booster.
  
  For more information, please see our Detailed Topic Vacuum Brake Boosters.
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- What are the symptoms of a leaking brake wheel cylinder?
  
  The symptoms will vary, based on the severity of the problem. With minor leakage, where the fluid is contained within the dust boot of the cylinder, the only symptom may be a slight loss of fluid in the master cylinder. As the condition gets worse, fluid can leak onto the brake linings. This can produce a grabbing or locking of the brakes on application. As the brake material becomes more saturated, we lose friction and the affected brake will not stop the vehicle. This often causes the remaining brakes to work harder, sometimes resulting in noise and/or a shudder on stopping.
  
  If the cylinder leaks enough fluid, we may lose the hydraulic action of the system. This can result in severely diminished stopping or possibly a loss of brakes.
  Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.
  
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- What are the symptoms of air getting into brake lines?
  
  Since air is compressible, the major symptom is always a low or soft brake pedal. That is, when the pedal is pressed, it travels farther and does not get firm until near the end of its travel. Hydraulic pressure in the brake line compresses the air and this acts like a spring causing the soft pedal. The process of removing air from the brake line is called bleeding. There are several methods of bleeding brakes, depending on the system. There is normally also a specific sequence in which the wheels are bled, depending on the vehicle.
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- What is automatic traction control?
  
  Design varies from one vehicle to another and operates similar to anti-lock braking systems (ABS). In fact many of the same components are used. Sensors read the speed of the drive wheels. This information is fed back to a computer that compares these wheels to the others. When a drive wheel increases speed to a predetermined percentage above the others, it is inferred to be spinning. At this point depending on the system, braking may be applied. Sometimes engine power is also reduced. Some systems may direct torque to the non-spinning wheel.
  
  When the spinning wheel slows to equals the other wheels, the system ends control and continues to monitor wheel speed. This may occur many times per second and switches among wheels as needed. Certainly this is a vast over-simplification but is the basic concept.
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- What is DOT 5 brake fluid?
  
  DOT 5 is a silicon based fluid, unlike DOT 3 and DOT 4 which are alcohol based. It is incompatible with and should never be mixed with alcohol based fluids. The advantage to DOT 5 is that it does not become contaminated with moisture like DOT 3 or DOT 4. DOT 5 is primarily used in restored older vehicles which do not have anti-lock braking systems (ABS).
  
  The rapid motion of the ABS components can cause DOT 5 to become aerated causing us to lose our brakes. Therefore DOT5 is not used in vehicles with ABS. Converting a vehicle from DOT 3 or DOT 4, to DOT 5, should always include replacement of every rubber component and thorough cleaning of all metal parts.
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- What is meant by discard measurement on brake rotors?
  
  Brake rotors are designed with a specific thickness in mind. This is important, not only for strength and heat dissipation, but to assure the calipers are not over extended when the pads wear out. The discard reading is the thickness below which the rotors should no longer be put into service.
  
  There is also a machine to limit, which is thicker than discard. This is the minimum the rotors can be safely machined to. It takes into account the amount the rotors will wear in the life of the pads.
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- What is the advantage of disk brakes over drum brakes?
  
  With a disk brake, there is no drum to retain water. This makes them more resistant to fade when driving though water. The spinning disk also tends to dissipate heat better than a brake drum. There are also fewer moving parts and disk brakes are inherently self adjusting.
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- What is the best brake pad for my vehicle?
  
  The brake pads originally designed for the vehicle, by the vehicle manufacturer have proven to us to give far superior service than aftermarket replacements. Rather than one material fits all, original brake pads are designed specifically for the vehicle. We have found they produce less noise, less dust, stop better and do not contribute to warping of brake rotors.
  
  It is also very important to realize that not all brake pads sold or installed by dealerships are original equipment manufacturer [O.E.M.] pads. For instance Dura Stop and Motorcraft pads sold by GM and Ford dealers are aftermarket products. Be certain to ask for and insist on original equipment manufacturer [O.E.M.] brake pads.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- What is the difference in a primary and secondary brake shoe?
  
  With duo-servo brakes, the primary brake shoe is the one that contacts the brake drum first. This causes both shoes to rotate slightly, with the brake drum, and forces the secondary shoe into tighter contact. The primary shoe is often in the front position and most of the time is slightly smaller than the secondary.
  For more information on drum brakes, please see our Detailed Topic, Solving Drum Brake Problems.
  
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- What is the difference in DOT 3 and DOT 4 brake fluids?
  
  DOT 3 and 4 are both alcohol based fluids and are compatible with each other. DOT 4 has a higher initial boil point than DOT 3, when both are fresh and uncontaminated. Because of the agents that give DOT 4 a higher boil point, it is also more susceptible to contamination. Moisture can enter the fluid and lower the boil point significantly. For this reason, DOT 4 should be replaced more frequently than DOT 3.
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- What is your opinion of the brake fluid test strips? They claim to detect copper in the fluid as a means of testing the corrosive potential of the fluid.
  
  The test strips work well and we use them in addition to refractive testing for moisture content. A possible draw back is they tend to detect corrosion that is already occurring. They are useful for folks that do not have records and need to know where they stand. An example is with a used vehicle inspection. Where possible, I find a better approach is to be proactive and replace the fluid about every two to three years. I feel this more likely preempts the corrosion issue.
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- When bleeding brakes, should I always start at the wheel furthest from the master cylinder?
  
  At one time that procedure was common. It can no longer be universally applied as many vehicles specify different bleeding patterns. Some vehicles use cross braking, with the left front wheel connected to the right rear. The right front is also connected to the left rear. It is not uncommon to see left or right front wheels bled first. From there some bleed the other front and others an opposite rear and so on. Most good shops refer to service data for the vehicle being worked on to be certain the right procedure is used.
  Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.
  
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- When I flush the brakes on my Chevrolet Impalla, how much fluid will I need and is one fluid better than another?
  
  Your Chevrolet specifies Dot 3 and will require about one quart to flush the system. Fluids labeled Dot 3 and Dot 4 are similar in chemical makeup. Dot 4 has a higher dry boil point but will become contaminated faster than Dot3. I always recommend putting back what the vehicle manufacturer specifies.
  
  Never buy more fluid than is required and dispose of any left over fluid. Dot 3 and 4 are very hygroscopic and will become contaminated in time, even in a resealed container. Even with the volume of brake fluid we use in the shop, we buy in quart containers. This helps ensure a fresh fill in each vehicle.
  
  My test have shown brake fluid in metal cans and with a metal seal at the neck, to be dryer than the plastic bottles. I would also suggest buying a major brand, from a supplier that does a high volume of business.
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- When I try to bleed my brakes the pedal keeps getting lower. What am I doing wrong?
  
  There are several methods of bleeding brakes, depending on the design of the brake system. Using the improper method will result in the pedal dropping and possible damage to the system.
  
  The means of applying pressure and the order in which the bleeder ports are opened varies considerably. The order is known as bleeding sequence and varies considerably from model to model. On older vehicles bleeding normally started at the wheel furthest from the brake master cylinder. With modern brakes there are several patterns. Using the wrong sequence can result in even more air being drawn into the system.
  
  Older systems also normally recommended pumping the brake pedal to produce pressure in the system. This will no longer work with many systems and can cause damage to the master cylinder. Instead, combinations of pressure tanks, vacuum and reverse pressure are often used. Many newer systems must have a factory scan tool to run the ABS pump in order to bleed air from the system. You will need to refer to the service data for your vehicle to determine the proper bleeding method and sequence.
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- When should brake calipers be replaced?
  We find that brake caliper life is influenced greatly by three main factors.
  1. The original design of the part. For instance, phenolic piston calipers are more susceptible to problems than metal piston types.
  2. The care they have received. For example keeping brake fluid fresh can extend caliper life. Driving in areas that heavily salt roads tend to create problems. Damaging the protective boots during other service will shorten life.
  3. Time; Age seems to be more of a factor than mileage.
  Calipers normally fail, either by leaking or by seizing. Leaks are fairly obvious and loss of brake fluid is a symptom. Some of the symptoms of a stuck caliper may be warped rotors, over heated brakes, pulling one way or the other on braking and uneven brake pad wear.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- When should brakes be replaced?
  That is an interesting question, with several answers. The short answer might be when they cause a problem objectionable to the driver or present a safety concern. Obviously when the brake pads wear out and begin damaging the rotors and drums they should be replaced. This is when the characteristic squeal or growl is heard. There are also times when people replace their brakes even though they are not worn out:
  - To address a noise concern, even though the pads may not be worn out
  - To correct a shudder or shimmy that occurs when braking
  - When a wheel cylinder leaks and the shoes are damaged
  - When other work in the area substantially lowers the cost of replacement at that time
  - To increase brake performance, even though the pads are not worn out
  - To avoid a future problem or for convenience
  The only true way to determine the condition of the brakes are with a physical inspection. Some wear out in as little as 20,000 miles and other go well over 150,000 without replacement. The design of the brakes and driving style are the two largest factors.
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- When should I flush my brake fluid?
  
  Testing brake fluid is somewhat difficult, but can be done with a refractometer or some types of test strips. In the absence of such devices two to three years is a good rule of thumb. Brake fluid should also be flushed BEFORE replacing any hydraulic component in the brake system. A search on the key words BRAKE FLUID on this site will also provide a good deal more information.
  
  $A brake fluid refractometer for measuring moisture content$
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- Which should last longer, rotors or brake pads?
  
  The answer depends largely on three factors. First the nature of the design. Many European vehicles wear out a set of rotors as quickly as the brake pads. Domestic and Asian vehicles normally will wear brake pads quicker. The second factor is the type of brake pad used. Harder pads wear rotors more quickly. Last is driving style. With aggressive braking, a set of rotors can be worn/warped quickly, regardless of the design. With easier/lighter braking and a proper set of brake pads, a set of rotors may last the life of the vehicle in many instances.
  
  For more information, please see our Detailed Topic Brake Shudder, Calipers and Noise.
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- Why do brakes need to be bled?
  
  Brakes use hydraulic force to apply the components. When the brake pedal is depressed, brake fluid pressure is tremendously increased. This pressure is what moves the pistons in the brake calipers, wheel cylinders and applies the brakes. Air can be compressed and acts like a spring. When pressure rises, the air is compressed rather than applying the brakes. This causes the pedal to sink and braking is diminished. This is often called a spongy brake pedal.
  
  Bleeding the brake system removes air that enters when the system is opened. Since the system remains sealed, fluid pressure will keep air from entering again.
  Please also see Basic Hydraulic Brake Diagnosis and Repair for far more detail.
  
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Electrical Systems and Warning Lights

After doing some under-dash work, my SIR light is on. How can I reset the light?

The supplemental inflatable restraint or SIR system is self-testing and resetting. When the light is on, there is an active fault in the system. Check all wiring connections, in the air bag system. These are normally color coded yellow for identification. When the problem, causing the fault, is corrected, cycle the ignition switch. The light will go out, after a short self-test.
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After having the water pump on my car replaced, the check engine light has come on. What is the best way to handle this with the shop?

While such things should not happen, sometimes they do. Best is politely to inform the shop that there is a problem and ask them to check it for you. Most shops will be happy to correct any problem, caused by their work.
It is also possible this is a coincidental occurrence and not related to the work they did. If this is what the shop finds, and you do not agree with their explanation, a second opinion would be appropriate. In the Detailed-Topics section, there is an article entitled When Things Go Wrong that has a lot more information on this topic.

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An oxygen sensor caused the check engine light to come on in my vehicle. What is the purpose of an oxygen sensor?

Oxygen sensors come in several types and serve different functions. Vehicles may have as few as one, or two, three, four or more. The basic function is to tell the power control module or PCM, how complete combustion has been. The PCM uses this information to control the fuel injectors and thus how much fuel is mixed with the air entering the engine.

When too much fuel is added, economy will suffer and components can be damaged. If there is not enough fuel, in relation to the air, running problems and damage to components can occur. Improper mixture can also result in damage to the catalytic converter(s) which can be extremely expensive.
Oxygen sensors are also used to monitor the function of the catalytic converter and test its efficiency, on post OBDII vehicles.
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Can an alternator bearing be replaced?

In most cases, it is possible to replace just the bearing(s) if they are available. This is sometimes done on very expensive or hard to find alternators. In most other cases, alternators are replaced with a rebuilt unit, because of costs. It requires significantly more time to replace the bearing than to install another unit. Time is money and it may be less expensive to replace the alternator rather than repair it. Other considerations are, when the bearing fails other components, such as brushes, diodes and even wiring, may not be far behind.
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Can corroded battery cables cause an engine to run rough?

Many things can cause an engine to run rough and while battery cables are not normally associated with this symptom, it is possible. Idle is a learned function on modern vehicles. The power control module (PCM) uses several inputs to determine idle. It also retains data, which allows for smooth idle under various conditions. Corroded cables can reduce system voltage and cause loss of this memory. When that happens, idle can be rough as well as several other problems.
For even more information on batteries and cables, see our Detailed Topics article, Replacing battery terminals.

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Can water short out an alternator?

Water can damage an alternator, but does not normally cause it to short out. Automotive alternators operate at less than 15 volts, and water does not readily conduct such a low voltage. Water can damage diodes, cause bearings to fail and promote internal corrosion, all of which can ruin an alternator.
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Can you help? I have an old Suburban and the left turn signal flashes very fast, while the right flashes at normal speed?

Rapid flashing of the turn signal, on this vehicle, often shows one of the turn signal lamps are not operating. Check all the bulbs in the left-turn signal circuit. I have also seen quite a few failures of the circuit board that holds the rear tail lamps.
Examine the plastic around the sockets in the circuit board. Often the center socket will be discolored. Replacement of the circuit board will normally get the lights flashing at a normal speed. Many technicians suggest to prevent future occurrences, replace the bulbs with an LED type of the same number. The LED bulbs draw lower amperage and may last longer.

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Codes P0174, P0171 and P0300 were set on my GMC Sierra. I had the intake gaskets replaced and 18 months later I have the same codes again. Why would this keep happening?

The 4.8L, 5.3L and 6.0L General Motors V8 engines had a good deal of problems with intake gasket leakage. We have found the fasteners that secure the intake contribute to the problem. When they are not replaced, with the intake gaskets, the problem will soon return. Another possibility is, the intake is warped too badly for the gasket to seal.
For more information, please see our Detailed Topic, GM V8 Rough Idle When Cold.

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Does being low on oil make a check engine light come on?

Some vehicles will set the check engine light with low oil pressure, because it interferes with engine operation. As a general rule, the check engine light means the vehicle computer system has encountered a problem it cannot resolve. This is an early-warning system to inform the driver a problem is occurring or is about to occur. Engine functions such as oil level, oil pressure and temperature generally have their own separate warning indicators.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.

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Does my replacement battery need to be the same size as the original?

Batteries have several specifications that make them work best in a particular vehicle. For instance, they have a specific number of cold cranking amps or CCA. A lower CCA battery may not crank the vehicle in all conditions. The correct amount is good, but more is NOT better. As CCA goes up, reserve capacity or RC goes down. Too many CCA will have insufficient RC.
The size limitations, terminal type and placement, vented and non-vented designs, hold down types are also critical.
Automotive batteries are normally assigned group numbers. A group number specifies the size and electrical characteristics of a battery. Matching the group number on the replacement battery with the original will greatly help in getting the correct battery.
For even more information on batteries, see our Detailed Topics article, Why Batteries Die.

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Does the check engine light come on for automatic transmission problems?

Most vehicles built after 1996 have sensors in the automatic transmission that allow the computer to monitor operation. A few things monitored are slippage, missed shifts, loss inputs, excess pressure adaptation and solenoid functions. OBD-II transmission codes will normally be numbered P0700 to P0799 and P1700 to P1799.
For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.

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Does the check Engine light come on when my vehicle needs routine maintenance?

The check engine light, more properly a malfunction indicator light (MIL) is not designed to track maintenance. Its purpose is to monitor the computer operating system and sensors that run a vehicle. When the light illuminates, a malfunction has occurred and needs to be addressed as soon as possible.
Neglecting maintenance for an extended period can cause a malfunction, in which case the light could come on. For instance failure to service an automatic transmission can cause it to fail, which could turn on the light. Properly performed, maintenance is a small investment to prevent major problems.

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Every so often, when I try to start my Toyota, I just get a click and it does not crank over. After a few tries it cranks fine. I have replace the battery and checked the cables.

The most likely cause would be the starter contacts. These contacts act as a solenoid and are inside the starter. They can be replaced without replacing the entire starter. As a diagnostic test, connect a volt meter between the battery terminal on the starter and ground. If there are 12 volts present, as the key is held in start position, and the click occurs, the contacts are likely the cause.

For more information, please see our Detailed Topic, Why Does The Engine Not Crank?

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How can I be sure I get the correct replacement vehicle battery?

The Battery Council International (BCI) assigns a group number to batteries that identifies their key size, post type and capacity characteristics. Matching the group number on the old battery with the replacement will ensure the battery will fit. The group number does NOT take quality of the product into account, however. When choosing a replacement battery, the advice of a trusted professional can be quite valuable.

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How can I check my fuel gauge to see if the problem is the sender or the gauge?

A fuel gauge that does not work at all, on an older vehicle can often be tested by removing the wire that connects to the sender unit. First remove the wire and then ground the wire. If the gauge now moves, the problem is in the tank. With newer vehicles and intermittent problems, it is significantly more difficult and almost impossible without training and instruments to read the digital feeds. On these vehicles, a scan tool is used to read the input from the tank and to check the function of the gauge.

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How can I tell how many amp alternator I have with out taking it off?

On any relatively modern vehicle, the vehicle identification number (VIN) can often be used. Anyone with access to a VIN parts database can find the options of the vehicle. Without this, the amperage rating is sometimes stamped on the case of the alternator, though it can be difficult to read. The vehicle option placard may also list the alternator option. These can be found on the driver's door, on most Chrysler's products. The option decal is often on the driver's door pillar on Ford's products. With General Motors, it may be in the glove box, truck or on the spare tire carrier.

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How does the check fuel cap light work?

The check fuel-cap light is an extension of the standard on board diagnostics [OBD] of the vehicle. The fuel cap is part of the evaporative emissions system. The engine computer tests to be certain the system is air tight. It does this by drawing a vacuum and seeing how long it will hold. If the system cannot achieve a vacuum, it assumes there is a gross leak and sets the check fuel-cap light. The system can be misleading as a number of other things can cause the same symptom. If tightening the cap does not rectify the problem, the evaporative emissions system should be checked.

Please see our Detailed Topic Evaporative Emissions Systems and Fuel Caps for more information.

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How does the warranty on a battery work?

Batteries may carry one or two warranties. The first is free-replacement and not available on all batteries. There will be a period of time in which the battery will be replaced without charge, if it fails. This period is normally six-months to two-years. This is an actual warranty.

The second type is the more common pro-rated warranty. Often these are little more than over-priced insurance, added to the cost of the battery. For instance the battery may have a six year warranty. If it fails in two years there is a cost per month for the time the battery was used. With pro-rated warranties, the cost of replacement often exceeds the price of a new battery, if the battery is a few years old. Generally, buying a battery with over a five year warranty is a waste of money.

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How many amps should my starter draw when cranking?

The exact amount will vary from vehicle to vehicle and even on the same vehicle from cold to hot temperature. Cranking several vehicles in the shop and measuring, provided an average of around 185 amps. This is with gasoline engines and at 70 degrees Fahrenheit. The highest was around 200 amps, and the lowest was 175, so I feel this is pretty typical.
For more information, please see our Detailed Topic, Why Does The Engine Not Crank?

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How much of a drain is the alternator on the engine?

Alternators take about one horsepower for twenty-five amps of output. A 125 amp alternator would require about five horsepower, when at the full charge. Because of this high-power consumption and because of the heat generated, modern vehicles regulate output to just above what is needed.

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I am taking a long trip, can an alternator be tested to determine if it might fail?

There is no basic test for overall failure. We can inspect the bearings with ultra sound, etc, but there is no guarantee of not having an electrical breakdown. The best protection is to remove the causes of alternator failure.

Number one and by a wide margin is low grade and old batteries. I replace my battery every three years and have never had to replace an alternator on a vehicle I owned. Weak batteries seriously overwork alternators.

Second is the belt, if it's old, it will slip and even though it may not make noise, can ruin the alternator. Lastly are the cables. They need to be clean and tight. Loose or corrode cables tend to kill alternators. If the ends are corroded, the cable should be replaced or professionally repaired [hydraulically crimped on ends]. Temporary, bolt on ends are a kiss of death to alternators.
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I had my timing belt replaced and after leaving the shop my ABS light came on after 10 miles. I returned to the shop and was told the ABS module had failed. I am very suspicious, what do you think?

That is quite a coincidence. Still things do happen and it is possible the two incidents are not related at all. I would discuss my concern with the original shop and tell them you would like a second opinion. Select a second shop agreeable to both of you and have them diagnose the problem. Should the problem not be related to the original work, and other work was satisfactory, I would return to the first shop for repairs.

Should a problem be discovered relating to the original repair, the first shop should be informed before any repair is made. This will give them an opportunity to inspect the damage and should make collecting for correction much easier.

In the Detailed Topics section there is an article entitled When Things Go Wrong that has a lot more information on this topic.
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I had the rack and pinion replaced in my vehicle and when I picked it up the air bag light was on. The shop says it is not related to the work they did. Could this be a coincidence?

Have the air bag system checked and see which code is present. If the clock-spring is damaged it is likely related to the rack and pinion job. If the steering wheel is turned with the rack and pinion removed or if the rack is not properly timed, the clock-spring can be damaged. If the fault code shows a problem in a non-related area, it could be coincidental.
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I have a light that says SIR, what does it mean?

SIR means supplemental inflatable restraint, more commonly called an air bag light. The system monitors speed and rate of deceleration to determine when the vehicle has been involved in a collision. Generally an impact at 12 MPH or more and within 12 degrees of center will cause the front air bags to deploy.

The system also monitors the status of the components, of which there are several. Very basically, there is are frontal crash sensors, arming sensor(s) bag modules, a clock spring assembly, wiring harness and an electronic control unit with backup power. Other systems also have seat sensor and active seat belt monitors included. When the key is turned on, the system goes to a self test mode and the light will remain on for a few seconds. Once the components are confirmed okay, the light goes out, signaling the system is ready to operate.

Failure of any component to test properly will cause the light to come on. A light on indicates a fault has been detected and the system may not deploy in a collision. Newer systems also have side air bags that deploy in side impact situations. There are several dozen things that can cause the light to stay on and only by diagnosing the system with proper tooling can the reason be determined. The problems can range from loose connections to module failures and cost vary widely depending on the problem.
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I have an odor, almost like rotten eggs coming from under the hood of my vehicle.

One source of such an odor is an over-charged battery. This may also be accompanied by corrosion on the cables as acid is often boiled out of the battery. When batteries over-charge, the fault will be in the charging system. The alternator or the control circuit will have to be checked to isolate the cause.

Another common source of rotten egg odor is the catalytic converter. This will normally be noticed coming from the exhaust.
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I have an older Chevy pick up that runs fine, but my air bag light stays on. What does this mean?

The air bag light, often labeled SIR for supplemental inflatable restraint, indicates the ability of the air bag to deploy in a collision. Being on, indicates that it may not inflate when needed and in some cases that it could deploy when it shouldn’t.

First check to see if the fuse is blown and replace it if needed. If this is the problem the light should come on for a few seconds when the truck is started and then go out and stay off. If the light remains on, or if the fuse is not blown, we can check the system and repair it for you. There are literally hundreds of possible causes of failure from a loose connection to a bad diagnostic module.
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I have code P0305, P0307 and P0132 on my Chevrolet pickup and it idles roughly. I have changed the O2 sensors, spark plugs, wires, distributor, cap and rotor. The same codes are still present. A friend says it might be the head gasket.

Parts changing is a VERY expensive way to attempt to correct a problem. Paying for an accurate diagnosis would have been far less expensive. The diagnostic trouble code (DTC) P0305 and P0307 indicate a misfire on cylinders five and seven. Code P0132 indicates voltage too high from the left bank O2 sensor.

Voltage too high means the left sensor is detecting too much unburned fuel in the exhaust. This might be expected with a misfire on the two cylinders, which are also on the left bank. Odds are the O2 sensor was fine. Specific cylinder misfires will be related to things specific to those cylinders. Swapping the spark plugs and wires with a cylinder that was not missing and checking the results would have revealed they were not the cause.

A logical step might be to check the engine compression. If compression is good and there is no evidence of coolant on the plugs in cylinders five and seven, a head gasket is not likely. A shop might run a fuel injector balance test as the next step. A stuck injector, leaking injector body or bad fuel regulator could account for all three codes.
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I have no brake lights and the shop is telling me it is the turn signal switch. How can the turn signal switch keep the brake lights from working?

Many vehicles use the same wiring and bulbs for the turn signals as they do for the brake lights. The turn signal switch cancels the brake light on the side selected by the turn signal, allowing it to flash. The turn signal switch is a possibility, especially if the high-mount brake light still operates.
For other things that keep brake lights from operating properly, please see our Detailed Topic How To Diagnose Brake Light Problems.

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I have one turn signal bulb that keeps going out. I replace it and about six months later it goes out again.

Repeated failure of a single light is often caused by a bad lamp socket. This is particularly common on the push in type sockets that are not spring loaded. Replacement of the socket will often cure the bulb issue.
For more information on light sockets, please see our Detailed Topic How To Diagnose Brake Light Problems.

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I have seen code readers advertised in several magazines. Can I save money by buying one of these and fixing my own vehicles?

Code reader can be of limited help as long as you also have the information and understand the operation of the system you are trying to repair. The diagnostic trouble code (DTC) only gives the computer’s interpretation of the area causing the problem and not a diagnosis.

For example a code could indicate insufficient exhaust gas recycle (EGR) flow. This does not mean the EGR valve is bad, though that is one possibility. It could also be the sensor that reads the flow, the wiring leading to and/or from the valve and sensor, plugged ports feeding the valve and many other possibilities.

Code readers do not give bi-directional communication with the vehicles computers which is often needed to isolate the malfunctioning part(s). It might be less expensive and frustrating to form a relationship with a professional shop, have them do the diagnosis and you replace the parts if you like.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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I have several weird electrical problems with my vehicle. Where is the best place to start looking?

With electrical issues we generally always start with the battery and cables. System voltage is critical and weak batteries, loose, corroded or improper cables create far more than their share of problems.

For even more information on batteries and cables, see our Detailed Topics article, Replacing battery terminals.
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I just bought a used Ford and noticed the fuel gauge wasn't working. What could be the problem?

The most common causes are either a bad fuel level sender (in the fuel tank) or a bad fuel gauge. If you are handy, locate the signal wire coming from the fuel sender. If you ground the wire the gauge should move to one extreme. If it does the gauge is likely okay and the sender is more likely the issue. If you don't care to try this, with a Ford scan tool, the gauge can be cycled and the sender output tested. This likely would not cost a lot to have tested.
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I put a locking gas cap on my car and now the check engine light comes on?

There are a great many designs of gas caps in common use. Different sealing areas, diameters, thread pitches and attachment styles. You may have gotten a cap that does not properly fit your fuel filler neck. If a cap does not form an air-tight seal, the evaporative emissions [evap] system will turn on the check engine light to indicate the fault.

Please see our Detailed Topic Evaporative Emissions Systems and Fuel Caps for more information.
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I was involved in a rear collision and the next day my check engine light came on. The code indicates EGR failure, could this be related to the accident?

The EGR (exhaust gas recycle) system is attached to the exhaust pipe on many vehicles. If the pipe were damaged, bent, broken or restricted it could cause an EGR fault. Excessive movement of the exhaust might also cause an EGR problem. EGR systems do also just fail at times and it may not be related.

A competent technician should be able to quickly identify the problem and by the nature of the failure determine if it relates to the collision.
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In the last few days a red light that says BRAKE comes on, remains for a several seconds and then goes back off. It seems to be related to turning a corner and accelerating.

Common causes of such behavior are low brake fluid or a bad fluid level sensor. Check the fluid level and if low top it off with the specified fluid from a new and unopened container [also see below]. If the light persist the sensor can be temporarily disconnected, as a diagnostic procedure. If the light now stays out, the sensor could be at fault. It should be checked by a professional or replaced, knowing there could also be other problems.

It is very important to fully check the braking system when fluid is low. There could be a leak or the brake material could be worn. It is not normal to have to add brake fluid and low fluid always indicates another problem.
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Is hot weather or cold weather worse on a car battery?

The answer is both. Temperature extremes of either type tend to kill batteries. A good deal of research points out that high temperatures actually kill the battery and low temperature reveals the damage.
For even more information on batteries, see our Detailed Topics article, Why Batteries Die.

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Is it possible for a fuse to look okay and still be blown?

Yes, a fuse may not appear to be bad, yet have failed outside of the visible area. A volt-meter is a quicker and more certain method when checking fuses.
For more information on checking fuses and relays, please see our Detailed Topic, How to check fuses and relays.

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Is there a way to disable the check engine light on my Suburban?

There is no way to disable the check engine light (MIL), nor any logical reason to try, in my opinion. On any post-1996 vehicle, the MIL is not the problem, it is merely indicating a problem. This system is fully integrated into the computer management of the vehicle and can check for about 2000 improper conditions. The MIL is simply trying to alert the driver to a condition that may cause more damage. In almost every case, early repair saves a great deal of additional expense.

Another way to think about it might be, a smoke alarm in a high rise building. The alarm brings attention to a bad situation. It does not say what the situation is nor what it will take to correct. A smoldering trash can may be quite easy to extinguish. Ignoring the alarm may result in loss of the entire building or worse.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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My ABS brake light is on but there are no symptoms.

An ABS warning light indicates the anti-lock brake system is not in an operable condition. This could be due to component failure, cut/disconnected wiring or parts in the system out of the proper range. Under normal operation, symptoms will not always be noticeable. Symptoms may only become apparent when the vehicle is in a brake lockup situation. When the light comes on, a code(s) will generally be stored. Retrieving the code(s) will identify the area of the system that is causing the problem. From there, testing of components is necessary to identify and correct the actual problem.
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My battery cables are corroded, should I replace the ends with bolt on terminals?

Bolt on replacement terminals are called emergency temporary terminals for good reason. They are a temporary repair at best and should be used only in an emergency. As with everything a diagnosis is in order, before repair.

First be sure the battery is not leaking, causing the corrosion. Leaking batteries are very common and the acid causes severe damage to vehicles. It can easily eat holes through brake, air conditioning, transmission lines and worse. If the battery is found to be leaking it should be immediately replaced and all traces of acid neutralized with baking soda and water.

Next check the cables to see if acid has “wicked” it’s way up the cable. With a sharp knife split the insulation back a few inches. If there is a white powdery appearance to the cables they must be replaced. If not they may be able to be repaired. Some cables are very expensive and repair is more practical than replacement.

With the proper equipment, a new end can be crimped onto the existing cable. Done properly this is a permanent repair and works as well as a replacement cable. AGCO can handle this repair for you if you would like.

For even more information on batteries and cables, see our Detailed Topics article, Replacing battery terminals.
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My battery terminal keep corroding and I was told my battery is leaking. My car starts fine, do I need to replace the battery?

Leaking battery acid is extremely corrosive and can do a great deal of damage to wiring, air conditioner lines and body panels. With the low cost of a battery, relative to the possible damage, it make no sense to not replace the battery.
For more information on potential problems from battery leakages, please see our Detailed Topic The Cost of Battery Terminal Corrosion.
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My brake lights are not working. How can I test for the brake light switch?

First depress the pedal and see if the third or center-mounted brake light works. If it does, the fuse and switch are likely okay. If not, check the input and output on the switch leads with a volt meter. If there is voltage going in, but not coming out, the switch is likely bad. If there is no voltage going in, check the feed circuit and fuse.
For more information on brake light problems, please see our Detailed Topic How To Diagnose Brake Light Problems.

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My check engine light came on about a year ago. The car still runs well but the light is still on. Is this anything to be concerned about?

Most definitely! Check engine lights do not come on without a reason. The one light can indicate approximately 2,000 different malfunctions, depending on the vehicle. Many malfunctions are initially quite minor, for instance a vacuum leak. If left unattended they can turn into major problems however.

Another problem, if the light is on, even due to a minor issue, and another problem occurs, you will not know. I would advise you to have the problem addressed immediately.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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My check engine light came on and a friend told me I should disconnect the battery and see if it goes off? Would you recommend that I do this?

I would never recommend disconnection of the battery to turn off a malfunction indicator lamp (MIL). Disconnecting the battery may temporarily turn out the light on some vehicles, but it also destroys the data a technician will need to repair the vehicle. Loss of this data can make correction of the original problem that caused the light to come on much more expensive.
Worse, other data that led up to the failure, that turned on the light can greatly speed the time of repair and reduce the cost substantially. This data and any fault codes are also loss when battery power is disconnected. Only a trained technician, after recording the needed data, should clear fault codes.
For even more information on check engine lights, see our Detailed Topics article, Failing State Inspection.

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My check engine light came on and after repair the invoice listed code P0304. Does this code have a specific meaning?

Yes, this is a generic on board diagnostics II (OBDII) code for a misfire on cylinder number four. Generic codes are set by the Society of Automotive Engineers (SAE) and are always five characters long. As a very general overview and currently, the first character is indicates which system logged the code.

P = Power train (engine/transmission, etc)
B = Body (Air conditioner/heater, body controls, etc)
C = Chassis (Steering, ride controls, etc.)
U = Undefined (Network, etc)

When the second character is 0 it indicates a generic code. A higher number indicates a manufacturer specific code and can vary from one make to another or even among makes.
The third character indicates the area that caused the code to set.

1 or 2 = Fuel or air metering
3 = Ignition or engine misfire
4 = Auxiliary emissions controls
5 = Vehicle speed controls and idle controls
6 = Computer output circuits
7 or 8 = Transmission

The forth and fifth digits or the specific condition that caused the fault. In your example the P indicates a power train concern, OBDII generic, misfire of cylinder number four. This does not indicate what caused the misfire only that it has occurred. With this information and additional testing a technician can determine the problem.
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My check engine light came on and stayed on all day. The next day it did not come on and has not come on in two days. Is this still a problem?

The malfunction indicator lamp (MIL) may often act in this way. The computer test the system and when it finds a problem turns on the MIL to alert the driver. When the ignition key is cycled the code is removed from current memory but retained in history. Depending on the problem and the vehicle, this may cause the light to go out. The light may then stay out until the computer runs this particular test again, which can take several days under certain conditions.

Complicating the strategy further are two trip and three trip codes. These faults must occur two or three times in a single key cycle to turn the MIL on. Several short trips can be made and never meet the conditions for light illumination, even though a problem exist. The vehicle should be checked by a professional technician as soon as possible.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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My check engine light is on and I am told it is the EGR valve. Can I still drive the vehicle with the EGR valve not working?

EGR or exhaust gas recycle lowers emissions and helps to prevent engine-damaging detonation, pinging and valve knock. The EGR valve opens when commanded and allows exhaust gas to enter the combustion chamber. This helps to cool the temperature and prevents spontaneous combustion of the fuel air mixture. Engine damage can result and there may be a loss of performance without the EGR system.
For more information on exhaust gas recycle or EGR valves, please see our Detailed Topic How does and EGR valve work.

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My check engine light was on so I had a friend clear the codes. When I went to get an inspection sticker I was rejected because the readiness test were incomplete.

When the codes are cleared on an OBDII vehicle, the I/M test are also cleared. This means the vehicle computer must test and pass all involved components. Until these test have completed and passed the readiness status will indicate incomplete. If a test fails, the check engine light will come back on.

For even more information on check engine lights, see our Detailed Topics article, Failing State Inspection.
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My check engine light was on, I had it repaired then it came on again. I returned to the shop, had more repair done and now it is on again. This is the third time in a year, it seems the shop is not doing something right.

Each time the light comes on there should be a diagnostic trouble code (DTC) stored in memory. It is important for the shop to list these codes on your invoice when repairs are made. With this information it should be easy to see if the same problem has recurred or if each visit is actually a different problem.

This is not necessarily a problem with the shop. Later model vehicles can have over a thousand causes for a check engine light. As annoying as it is, you must remember there is only one light and many problems that can turn it on. Another issue is that most sensors [a prime cause of problems] have a service life of about 100K miles. It is not unusual to see several fail at this milage.
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My driver’s side low beam headlight keeps going out. I have changed it three since I bought the car in 60,000 miles.

Short bulb life, on a single bulb, is almost always one of a few things. First is a loose connection somewhere in the circuit. The connection causes voltage fluctuation, too fast for the eye to perceive. The effect is a shortened life for the bulb. Favorite offenders are the bulb socket, any connector in the circuit and sometimes the switch. The ground side of the circuit is equally important, and a loose ground causes the same problem.
The second cause is a loose mounting that allows the bulb to vibrate. Excessive vibration will break the filament inside the bulb. Finally, a crack or hole in the headlamp housing allows moisture in, and this will cause the hot bulb to fail.

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My engine would not crank when I turn the key. I replaced the starter relay, it tried to crank, but the relay immediately burned out. What would cause this?

Connections and relays almost always burn because of excessive amperage flow. First check to make sure the engine and all accessories on it rotate freely. You can check by putting a wrench on the large crankshaft nut and turning the engine by hand. If the engine turns freely and smoothly, I would suspect a shorted starter motor. Have the amperage draw of the motor checked.
For more information, please see our Detailed Topic, Why Does The Engine Not Crank?

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My Maxima's starter has begun to occasionally miss engaging the ring gear on start-up and makes a loud ZING! Which rebuilt starter brand is the best to use?

First, be certain the starter is the problem. Nissan has a rebuilt starter sold through their dealers and I have found it to be of very high quality. I have seen people have poor results with other rebuilt brands and we replace them with Nissan supplied starters quite frequently.
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My truck quit running two weeks ago. A friend checked it and told me there was no fuel pressure. I replaced the fuel pump and it ran for a couple of hours and then died again. Do you think this pump is defective?

Anything is possible, but a flaw in the diagnosis could as likely be the problem. Lack of fuel pressure does not mean the fuel pump is bad or that a bad fuel pump is the only problem. The fuel pump must have power and ground to operate.

Power and ground at the pump with no fuel pressure would indicate a bad pump. Since you did not mention checking these, I would start with them. A bad fuel pump relay, or a bad wiring harness could prevent power from reaching the pump.

Some vehicles even have circuits that disable the pump under certain conditions, such as an oil pressure switch. If the switch does not see pressure, it cuts the fuel pump. It might be prudent to test the electrical circuitry before changing any additional parts.
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My vehicle came equipped with ten-ply tires. The tire pressure monitoring system was set for 50 PSI. I would like to reduce the air pressure to improve ride. Can I do this without making the warning light come on?

It is not advisable to ever go below the Vehicle manufacturers recommend tire pressure. It is normally calculated with ride as a primary concern and should be considered the minimum allowable. Tire pressure monitoring systems (TPMS) take this into account and will illuminate if pressure is set below the recommended amount.

Also see our tire pressure article for a great deal more information.
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My vehicle failed the State emissions inspection and I was told it was because my cigarette lighter did not work. How can that be?

In order to test the onboard emissions system, many States connect an electronic device to the vehicle. These connector used is often powered through the cigarette lighter or accessory plug. If the device does not show a power source, it will often register a failed test. We repair quite a few lighters and accessory plug systems for this reason.
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My vehicle was recently wrecked in the front but the air bag did not deploy. Is this a defect?

Air bags or supplemental inflatable restraints (SIR) only deploy under certain conditions. For instance the impact normally has to be in excess of 12 MPH. It may also have to be within so many degrees from center of the vehicle, (e.g., an impact 20 degrees off center may not deploy the bag and one 5 degrees may.) These systems are quite well tested and an onboard computer monitors their status. Chances are if the SIR light was not on, indicating a fault, the impact did not meet the criteria for deployment.
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Only my top brake light is working and not the two main brake lights. The turn signals work and the hazard flashers work as well. All fuses are okay.

A likely cause may be the turn signal switch or the connectors on it. If the hazard lights work, the wiring, bulbs and sockets are working. If the third light comes on, the fuses and brake light switch are working.

The turn signal switch interrupts the brake light, on the side that is flashing. If it did not, the light could not flash. When the switch or connection fails, it can interrupt the lights when it should not.
For more information on brake light diagnosis, please see our Detailed Topic How To Diagnose Brake Light Problems.

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Recently I had to have head gaskets replaced on my vehicle. The shop said the car had been over heated, but the warning light never came on. Is this possible?

Many times overheating is caused by low coolant, resulting from leakage. The coolant reservoir replenishes the radiator, until it runs empty. With no reserve coolant the radiator runs low and the coolant level drops in the engine. Unfortunately, on many vehicles when this happens the electronic coolant temperature (ECT) sensor may no longer contact the coolant. Under these conditions the engine can overheat and not indicate this to the driver.

Warning lights and gauges are very handy reminders, but are not error-proof. A quick inspection of fluid levels, on a regular basis is a very good idea. Also be aware, that once the coolant reservoir gets empty, filling it may no longer fill the radiator. The syphon effect is loss once the radiator gets low. Allowing the vehicle to completely cool and filling the radiator with the proper pre-mixed coolant is necessary to restore operation. It is also NOT normal for the reservoir to require additional coolant. A low reservoir indicates a problem.
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Recently my vehicle air conditioner was repaired. Shortly after picking the vehicle up, the check engine light came on. Could this be a coincidence?

It could be, there are almost 2000 possible reasons a check engine light can come on. It could also be related to the repair. They may have inadvertently left off a vacuum hose or possibly left a sensor disconnected. If so, the repair should be very minor and no charge to you. By having them retrieve the diagnostic trouble code (DTC) in memory, it should be reasonably easy to establish if the problem could be related to the repair.

Most quality shops would welcome the opportunity to correct the mistake. If the shop feels it is not related to their work and you feel it may be, a second opinion from another qualified shop may be in order. In the Detailed Topics section there is an article entitled When Things Go Wrong that has a lot more information on this topic.
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Several alternators have been replaced on my vehicle. Is this just poor quality parts?

Very poor quality parts are quite common and that is a possibility. Batteries and improper cables can also cause alternators to fail. An undersized battery or one that is weak can cause the alternator to work much harder than normal. Poor cables can have high resistance and quickly ruin an alternator as well as several other components. Finally a weak belt tensioner or loose drive belt can slip and damage an alternator.

For even more information on batteries and cables, see our Detailed Topics article, Replacing battery terminals.
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Some part stores offer to read codes for free when a check engine light comes on. What is the advantage to having a professional diagnosis?

This practice is popular with part stores because it sells a lot of parts. Most professionals see people each week who have spent hundreds on unneeded parts from this. Many people learn the hard way, a professional diagnosis is the least expensive way to fix the problem.

A diagnostic trouble code (DTC) only shows why the computer turned the light on and not what is wrong with the vehicle. For instance a vacuum leak, bad air flow meter, clogged injector, bad coil, bad plug or many other things can set an oxygen (O2) sensor code. The sensor is out of range because of other factors in the engine and replacing it will have no effect. Save money, a free diagnosis is much too expensive.
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The ABS light came on and the wheel speed sensor was replaced. Less than a year later the light came back and the sensor was again replaced. Two weeks later the light is back on. Why does the sensor keep failing?

Likely the sensor does not keep failing and the actual cause of the problem is being mis-diagnosed. For instance a bad connector could cause the ABS light to come on and display a sensor code. Replacing the sensor and re-connecting might clear the problem temporarily. Eventually the connector again may lose contact and the cycle repeats. Many things can cause a sensor code other than the sensor. Best might be to try another shop, giving them the full history of what has occurred.
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The air conditioner blower in my vehicle quit working. I replaced the blower resistor and it worked for a while and quit. Could the switch be bad and how can I check it?

The switch does fail as well as the connections going to it. With a volt meter power going in can be tested. If there is power going in and none coming out, the switch is bad. A physical inspection will normally reveal burned connections.

My experience has been, when switches and connectors burn, the motor is the normal cause. As motors age, they can start drawing more current to operate. If the motor pulls much in excess of ten amps, it may burn the up-line components. In every case where I see repeat resistor and switch issues, the problem is normally resolved by also replacing the blower motor.
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The anti lock brake light is on in my vehicle, but no codes show with a code reader.

Modern vehicles have several computers. Some have up to twenty different modules. They communicate with one another but do not always share diagnostic information. For instance an ABS code may be stored in the body control module (BCM) and not the power control module (PCM.) Retrieving codes from body, transmission, air bag, climate control and other modules normally requires original equipment manufacturer’s level tooling. These cost several thousand dollars and different tools are required for different makes and even different years within a vehicle line. It will likely be necessary to refer this problem to a professional with the proper tooling.
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The battery in my vehicle goes dead over night. If I disconnect the cable from the battery and reconnect in the morning it is good. What could cause this?

This sounds like a parasitic draw on the electrical system. That is, something is staying on and drawing current when it should not. There are countless possibilities, some of the more common are glove box lights, trunk lights, and accessories.

First turn everything off in the vehicle that can be turned off and disable the door light switch, if the door needs to be opened. Diagnosis begins with connecting a sensitive amp meter inline with one of the battery terminals and it’s cable. If the meter reads current flow above a few hundredths of an amp there is a problem. Remove fuses from the fuse box(s), one at a time until the meter drops. This will identify the circuit with the draw.

Once the circuit is identified you will need a wiring diagram to learn what is on that circuit. Each component would then need to be disconnected until the draw diminishes. Once identified the component can be repaired or replaced as needed.

For even more information on batteries, see our Detailed Topics article, Why Batteries Die.
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The brake lights on my Honda Accord are staying on, even though the pedal is not being pressed. What would cause a problem like this?

There is a small stopper on the brake pedal, where it contacts the switch. In time the rubber may deteriorate and the stopper may fall out. The pedal no longer contacts the switch, so the brake lights are not turned off when it is released.
For other things that keep brake lights from operating properly, please see our Detailed Topic How To Diagnose Brake Light Problems.

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The center brake light on my vehicle lights but the regular brake lights do not. The fuse, bulb, sockets and brake switch all test good. What could be the problem?

Brake lights often route through the turn signal switch and use the same bulbs. If this is the case check the input and output of the turn signal or multi-function switch. This is a common failure point.
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The check engine light came on and a part store told me it was the gas cap. I replaced the cap and the light is still on. How can this be?

Check engine light diagnostics is a complex field and reading a code in memory is not determining what is wrong. There are several dozen things that can cause any given code and only by proper diagnosis can the actual problem be determined. Swapping parts is very expensive and not at all effective.
Please see our Detailed Topic Evaporative Emissions Systems and Fuel Caps for more information.

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The check engine light is on in my Yukon and I was told the intake manifold is leaking. I can see nothing leaking under or around the vehicle.

Most likely the shop is speaking of a vacuum leak and not a fluid leak. When an intake manifold leaks vacuum, air is drawn through the leak and disturbs the fuel/air mixture. This can result in a check engine light with no physical leak that can be seen.
For more information, please see our Detailed Topic, GM V8 Rough Idle When Cold.

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The Check Engine light on my Ford is on. I took the vehicle to a part store and was told I needed an EGR valve. I bought the valve, replaced it, but the light still comes on.

The Check Engine or more properly Malfunction Indicator Light (MIL), is a symptom indicator. The Diagnostic Trouble Codes (DTC) stored in memory are not to be taken literally, only as an interpretation of the circuit creating the problem.

In this case the DTC may have indicated something like Exhaust Gas Recycle (EGR) flow insufficient. This does not mean the EGR valve is bad. It means the engine computer sees a problem with the system. This problem could be the result of several things.

For instance the sensor that tells the computer that the valve is flowing could be malfunctioning. The hoses that provide input to the sensor could be bad. A connection could be loose or the passages that flow exhaust to the valve could be plugged. These are only a few of the possibilities and listed to make a point.

The point is, it is much less expensive to have the system properly diagnosed. Paying for a professional diagnosis would have saved the cost of the EGR valve. Replacing parts, without knowing the actual cause of the problem is expensive and seldom solves the problem. Some part stores advocate this approach, for obvious reasons.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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The check engine light was on in my car. A parts store cleared the codes but my car still failed inspection.

Whenever a problem occurs on the vehicle that can affect emissions, the check engine light is set. At the same time a diagnostic trouble code (DTC) is stored in history. Clearing the code will not repair the cause of the problem. When the memory is cleared, the registers for test results are also cleared. When this happens, the vehicle will begin testing every component and marking it as passed or failed. If you attempt inspection before the test are complete, the vehicle will fail for that reason. If the original problem has not been corrected, the light will again come on when the test is run.

For even more information on check engine lights, see our Detailed Topics article, Failing State Inspection.
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The company I work for rents a van from a large rental firm. The check engine light is always on and when we bring it to the rental companies attention, they simply clear the code. The next day the light is back. Should I be concerned?

I feel you have every right to be concerned. The check engine light indicates an emissions or running problem with the vehicle. Ignoring the warning is irresponsible and possibly illegal. Many areas have laws against driving with a check engine light. When you further consider the cost of [premature] replacement of the vehicle is covered by the cost of rental you should be concerned. A letter to the agency manager with a CC to the main headquarters and your manager may help. If not, I would select another company from which to rent.
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The fuel gauge on my Impala shows 1/4 tank but the driver information center reads low?

Both the gauge and the information center read off the same sender unit. If the sender were bad, both would read improperly, but agree in reading. A likely cause would be the gauge in the dash. You could verify this by filling the tank and noting the amount of fuel taken. Compare the amount added to the capacity of the tank. If considerably more than three-quarters of the fuel capacity can be added, the gauge is the likely problem. If very close to three quarters fills the tank the problem would more likely be in the drivers information center.
Please see our Detailed Topic article GM Dash Gauge Failure for far more details.

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The low coolant light came on in my vehicle and the coolant reservoir was empty. I filled the reservoir but the light is still on. Do you think the level sensor is the cause?

The coolant level sensor could be the cause, but you should also physically verify the coolant level. When a cooling system gets low it can draw air into the system. Once air has entered the system the reservoir may no longer function to fill the system.

Wait until the vehicle is completely cooled and remove the radiator cap. If the level is low, fill it with the specified coolant and distilled water, premixed half and half. Replace the cap and see if the light is out. If not, the warning light problem is likely with the level sensor circuit.

Whether the light goes out or not the vehicle needs to be tested and the source of the leak repaired. The system being low indicates it is leaking and this can cause severe damage if left unattended.
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The oil pressure gauge in my Chevy Suburban moves from zero to maximum when I start the truck. Could this be the gauge?

More likely if the gauge returns to zero when the engine is turned off the gauge is not the fault. The oil pressure sender unit on these vehicles is a very common failure item and a more likely cause. Temporarily unplug the sender unit and if the gauge falls to zero, the sender is more likely the cause.
Please see our Detailed Topic article GM Dash Gauge Failure for far more details.

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The oil pressure gauge on my GMC Sierra is stuck all the way on high. Do I have to take this to a GM dealership?

The 2003 through 2006 GM truck instrument panel cluster (IPC) was under recall up to 70,000 miles. In order to have it repaired under the recall, you would have to return to a GM dealership. If you are out of the recall mileage, any independent shop can make the repair for you, often at a lower cost.

Please see our Detailed Topic article GM Dash Gauge Failure for far more details.
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The oil pressure light came on in my car while I was driving. I stopped checked the oil and it was full. When I started again the light was out but later came on again, does this sound like a major engine problem.

Not necessarily, but do not continue to drive the vehicle or it may become one. The first step in diagnosing the problem is to verify the oil pressure with a mechanical gauge. If the pressure is within specifications the problem could be a simple as a bad oil pressure sender unit.

If the pressure is below specification it is imperative to determine and repair the cause before driving the vehicle. Severe damage occurs very rapidly when oil pressure drops.
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The speedometer of my Chevy Suburban often sticks and reads improperly. I was told this was under recall, but the dealership told me it had expired. What is the term of the recall?

The 2003 through 2006 GM truck instrument panel cluster (IPC) is normally under recall for up to 70,000 miles. This may be negotiable for another 10,000 miles, depending on the circumstances. In order to have it repaired under the recall, you would have to return to a GM dealership. If you are out of the recall mileage, any independent shop can make the repair for you, often at a lower cost.

See our Detailed Topic article GM Dash Gauge Failure for far more details.
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The terminals of my battery keep corroding. I clean them and within a few weeks it has occurred again. Is there a way to prevent this?

Corrosion as you mention is normally caused by acid leaking around the terminals of the battery. This is easily tested detected with a pH test strip. Just lay it on the battery and if it shows acidic (below 7.0) the battery should be replaced.

Escaping acid from a battery can do severe damage. Air conditioning lines, transmission lines, the radiator, electrical system and the body of the vehicle can all be damaged by exposure to battery acid. The area of the battery should be thoroughly cleaned with a solution of baking soda and flushed with clean water.

For even more information on batteries and cables, see our Detailed Topics article, Replacing battery terminals.
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This morning when I went to start my car there was a click, click noise and the engine would not crank over. Do you think this is just the battery or should I have the electrical system checked?

I feel it unwise to just replace a battery, without checking the electrical system. Many times a dead battery is a symptom of another problem. A weak or bad alternator or even a parasitic draw on the system will result in a dead battery. Replacing the battery may not be necessary and even if necessary may not be the full problem.

Looking at overall lowest cost, checking the system is a lot less expensive than replacing a battery, only to have it ruined by a bad alternator. Just as bad is replacing a battery to find something else is causing the problem, and the battery was not needed.

For even more information on batteries, see our Detailed Topics article, Why Batteries Die.
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What are the symptoms of a bad alternator?

Alternators can fail in a number of ways. Most failures result in a lack of charging and an eventual dead battery. Sometimes the internal bearings fail and although they may continue to charge for a while, there will usually be a whining noise. Partial failure of the diodes can also result in current discharge back through though the alternator when it is not turning. Modern alternators are usually controlled by the power control module and are difficult to test without sophisticated equipment. For that reason, they are sometimes mis-diagnosed and replaced needlessly.
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What do OBDII codes actually mean?

Generic on board diagnostics II (OBDII) codes each refer to specific systems, components and faults as follows.

The first symbol
P = Power train (engine/transmission, etc)
B = Body (Air conditioner/heater, body controls, etc)
C = Chassis (Steering, ride controls, etc.)
U = Undefined (Network, etc)

When the second character is 0 it indicates a generic code. A higher number indicates a manufacturer specific code and can vary from one make to another or even among makes.
The third character indicates the area that caused the code to set.

1 or 2 = Fuel or air metering
3 = Ignition or engine misfire
4 = Auxiliary emissions controls
5 = Vehicle speed controls and idle controls
6 = Computer output circuits
7 or 8 = Transmission

The fourth and fifth digits or the specific condition that caused the fault. For example P0304, the P indicates a power train concern, OBDII generic, misfire of cylinder number four. This does not indicate what caused the misfire only that the computer thinks it has occurred. With this information and additional testing a technician can determine the problem.
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What does a flashing over-drive light indicate?

Some vehicles use the over-drive light to indicate transmission malfunctions. This is very much the same as the engine uses the check engine light. On some models, when the automatic transmission computer encounters a problems, it flashes to alert the driver. On other vehicles, the check engine light is used for both engine and transmission. When either light comes on, a diagnostic trouble code is stored.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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What does the check suspension message on my Lincoln indicate?

The air suspension system is controlled by a computer that optimizes ride height for handling, ride and tire life. When the system has an electrical malfunction, the check suspension message will be displayed. Unfortunately, the system only monitors the electrical functions and not leaks. Many times, electrical failures, such as a bad suspension air pump, are caused by over-running the pump, due to a leak.

For more information please see our Detailed Topic Ford Air Suspension Problems.
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What does the dash gauge marked RPM do?

The gauged marked RPM is a tachometer and measures the revolutions per minute the engine is turning. This is helpful in knowing when to shift and as a diagnostic gauge to check vehicle speed against engine speed.
For more information on the gauges on the dash, please see or Detailed Topic, What Do The Gauges on The Dash Mean.

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What does the light labeled “Check Engine” indicate?

The check engine, more properly malfunction indicator lamp (MIL) means one of the vehicle’s computers has encounter a situation it cannot handle. It does not check the oil, coolant, battery or maintenance due.

On a modern vehicle there are over 2000 things that can make the light come on. A sensor that is out of range, not reading or disconnected. A vacuum line that is disconnected or plugged. An engine taking too long to warm up or a plugged fuel injector. Even a fuel cap not sealing tightly can illuminate the MIL.

This is the vehicle’s way of letting you know a situation exist that will cause a problem. Special tooling allows a trained technician to determine the cause and correction needed. Ignoring the MIL, even if the vehicle seems to be running fine will almost always result in a far worse problem or breakdown.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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What does the term OBDII mean in reference to my vehicle?

OBDII stands for on board diagnostics II and refers to a standardized system administered by the Society of Automotive Engineers (SAE). In the shop it is often used in reference to diagnostic trouble codes (DTC) used to help determine what is wrong with a vehicle.

For even more information on check engine lights, see our Detailed Topics article, Diagnostic Trouble Codes.
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What is a starter solenoid and how does it work?

The starter solenoid is a magnetic switching device. It allows a small amount of current, controlled by the ignition switch, to start the vehicle. When the ignition switch is turned a small current activates an electromagnet. This magnet closes heavy contacts that allow almost 200 amps to flow to the starter.
For more information on starter solenoid operation, please see our Detailed Topic, Why Does The Engine Not Crank.

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What is an automotive O2 sensor used for?

Oxygen sensors help control fuel mixture and reduce emissions. They determine how much oxygen is needed to completely oxidize any fuel remaining in the exhaust. Unburned fuel requires more oxygen and increases the voltage output. The computer sees this as a rich mixture and with other sensors reduces the time the fuel injector remains open. This causes the fuel air mixture to lean out or have less fuel, per air volume. Less fuel in the exhaust takes less oxygen to oxidize and cause the voltage from the sensor to drop.

Oxygen sensor are also used to check the efficiency of catalytic converters. They do this by checking before and after the converter and comparing the readings.
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What is needed to test an automotive relay?

Standard automotive relays can be tested with an ohmmeter. Many have a schematic printed on them and most use a standard pin pattern.
For more information on checking fuses and relays, please see our Detailed Topic, How to check fuses and relays.

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What is the average life of an automobile battery?

The average life of an automobile battery across the US is about 38 months. This is considerably shorter than a few years ago. Increased demand on electrical systems is partially to blame for the decrease.
For even more information on batteries, see our Detailed Topics article, Why Batteries Die. >.

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What is the difference in a deep cycle and regular car battery?

The difference is the way they are designed. Deep cycle batteries are designed to produce a steady current over a long period of time. A trolling motor in a boat would be a good candidate for a deep cycle battery. An automobile on the other hand requires a large amount of current to crank the engine, but only for a short period of time. The alternator supplies the steady demand for power, once the vehicle is running. For this reason, car batteries are designed to produce much larger amounts of current, but not for as long a period.

For even more information on batteries, see our Detailed Topics article, Why Batteries Die.
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What is the difference in a deep cycle battery and a regular car battery?

The difference in a deep cycle and normal automobile battery is basically how much power they produce and for how long. Normal automobile batteries are designed to produce a large amount of amperage, for a short time. This is to produce the energy to crank the engine when cold.

Deep cycle batteries are not designed to produce as much amperage, but they can provide power for longer periods of time. For instance a trolling motor in a boat, does not draw a large amount of current, but may be used for several hours. A deep cycle battery may not produce enough current to crank a car, and a car battery may not survive a long discharge period without recharge. Each type has a specific purpose.
For even more information on batteries, please see our Detailed Topics article, Why Batteries Die.

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What is the purpose of an alternator?

The alternator converts mechanical energy of the engine into electrical energy. This energy is used to operate the various electrical devices in the automobile when the engine is running. The alternator also replaces energy used from the vehicle battery when the vehicle is not running. Without an alternator the vehicle battery will soon expend all of its energy and go dead.
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When I turn my ignition switch to start I hear a loud click, but nothing else. Sometimes it will do this several times and then start. This is a General Motors vehicle.

This problem is often caused by worn starter solenoid contacts. To isolate the problem an inductive amp meter should be connected to the positive cable and a volt meter to the starter terminal. With the symptom duplicated, see if amperage is very low and the voltage is normal. If so check voltage at the terminal that leads from the solenoid to the motor. If voltage is not present when the symptom occurs this is quite likely the problem. If milage is high, it may be most cost effective to replace the entire starter with the solenoid.
For more information, please see our Detailed Topic, Why Does The Engine Not Crank?

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When should I replace my vehicle battery?

Many experts state the average life of a car battery is about 38 months. This will vary somewhat, but in our experience is about right. Weak batteries can damage the alternator, starter and cause all sorts of electrical problems. With the fairly low cost of a battery, relative to the service it provides, I feel changing it before failure is wise. I normally recommend replacing the battery around 36 months. This allows the client to have it done at their convenience, rather than as an emergency.

For even more information on batteries, see our Detailed Topics article, Why Batteries Die.
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Why is the starter on my new car much smaller than the one on my older car?

In the early nineties, car makers started using permanent magnet, gear reduction starters. These are physically much smaller, lighter and have fewer parts. Our experience has been they work very well and last much longer than the much larger starters of the past.
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Why would my vehicle battery overheat?

In most cases overheating is caused by over charging. On older vehicles limiting the charge was a function of the voltage regulator. On newer vehicles, system voltage is controlled by the power control module (PCM.) Over charging a battering will drastically shorten the life and can be quite dangerous. A charging battery produces gasses which can be explosive. Best is to have the vehicle checked immediately.
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Without test equipment, is there a way to determine the cause of a misfire on an old carburetor type engine?

A good starting point in fixing a misfire is to determine if you have a single cylinder or multiple cylinder problem. Without other equipment, a good way to determine this is with a vacuum gauge. Attach the gauge and note the reading. Remove the spark plug wires, one at a time, with the engine running. The vacuum should drop about the same amount when any wire is removed.
IF it does not drop on any one cylinder, that cylinder is where the misfire is occurring. Swap the spark plug and wire with one on a cylinder that is not misfiring. If the misfire moves, the plug or wire is bad. If not check the compression on the engine and see if it that cylinder is low. IF the compression is low, the problem is likely an internal engine problem.
If all cylinders make about the same difference, when the plug wires are removed, the miss is likely affecting all cylinders equally. This could be the caused by the carburetor, a bad vacuum leak, mis-routed plug wires or other things that affect all the cylinders equally.

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Would a bad brake caliper cause the ABS and Traction control light to come on?

It is possible under extreme conditions, but not likely. The caliper would have to seize, stop or drastically overheat the brakes. If this occurred the cause would likely be fairly obvious.

Far more likely is an electrical issue in the system, such as a failed sensor, brake control module, etc. A qualified technician with the proper tools should be able to isolate this problem fairly quickly.
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Would a deep cycle battery last longer in a vehicle I do not drive often?

It may not last as long as a standard battery. Deep cycle batteries produce current over longer periods, but also require longer recharge times. If the vehicle is not driven much this could cause it to die even sooner. A better plan might be to use a computer controlled auxiliary charger, designed for the purpose, or try to drive the vehicle more.

For even more information on batteries, see our Detailed Topics article, Why Batteries Die.
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General Automotive

A control solenoid has failed on the EGR system of my vehicle. Is this dangerous? Are poisonous gasses being released?

The exhaust gas recycle or EGR system is designed to help reduce vehicle emissions and reduce valve clatter on acceleration. There is no safety concern when it malfunctions. The transfer of exhaust gas is internal to the engine. There may be an increase in vehicle emissions from the engine and the system should be repaired as soon as possible.
For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.

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A friend and I have an argument. He says three to four feet is the proper distance between you and the vehicle in front of you when stopped in traffic. I think this is too short. Who do you think is right?

As a general rule, if the driver cannot see the tires of the vehicle ahead, touching the road, they are too close. This normally works out to about eight to ten feet. Better safe than sorry?

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A friend convinced me to add gas treatment to my vehicle. I accidentally dropped the cap down the filler pipe. Will it cause damage?

The fuel additive is likely more damaging to the car than the cap falling into the tank. The screen on the fuel pump will prevent the cap from causing a problem. Adding foreign chemicals to gas is not necessary or advisable. Name brand fuel has all additives the vehicle needs and will not cause damage.
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A mechanic told me my car had a blown head gasket. The engine keeps overheating, but there is no coolant in the oil. How can I have a blown head gasket with no coolant in the oil?

Head gaskets fail in many ways. If the gasket has not failed between the coolant system and an oil passage, the oil may remain fine though the vehicle could over heat. For more information on coolant in the oil, please see our Detailed Topic Coolant in Engine Oil for more details.
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After driving and letting my vehicle sit an hour or so, it cranks several times before starting. Other times it starts just fine. We replaced the fuel pump but it is still the same.

Fuel pumps can cause a similar problem by allowing fuel to drain back to the tank. Normally this will cause a hard start in the morning or after sitting for a period of time. A common cause of the complaint you list is a leaking fuel pressure regulator, on vehicles that use them. Fuel can leak through the regulator diaphragm and lower pressure on the rail. At the same time the fuel enters the intake. This causes an over-rich condition and also makes starting more difficult. Check by removing the vacuum hose from the regulator. Any fuel in the vacuum hose indicates a need for replacement.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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After replacing the battery, my car would die at idle. After a while it now idles okay again.

If the engine idles too low it will die. Idle speed is a learned function. That means, using several inputs, the engine computer learns where idle needs to be. Disconnecting the battery may cause this memory to be lost.

To help speed relearn, try putting the vehicle in park (neutral) and let it idle for about two minutes. Next turn the air condition on, if so equipped. Again let it idle about two minutes. Next shift into drive, with your foot on the brake and let it idle for two minutes, if it has an automatic transmission. This should help a great deal and final idle will be learned after a bit of driving.

For even more information on batteries and cables, see our Detailed Topics article, Replacing battery terminals.
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An extended warranty company insists on putting aftermarket parts on my vehicle. Is this legal?

Only a court of law may say what is legal. An extended warranty is a contract between the warranty company and the client. The terms of the contract, although they may be hard to read or understand, are the terms of the agreement. If the policy states used, rebuilt or aftermarket parts will be used, that becomes the agreement the client has entered. This is unfortunate as in my experience, most folks do not consider this when buying the extended warranty.
For more information on extended warranty problems, please see our Detailed Topic, Extended Warranties, Avoid The Hook.

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Are dealership service departments free to interpret TSBs, leaving out parts as they see fit?

A technical service bulletin is loosely a piece of advice, based on experience the manufacturer has encountered. This makes it different than a recall or even a warranty item. Unless the repair is being paid for by the manufacturer, such as warranty claims, a dealership is exactly the same as any other shop. They are free to repair the vehicle in any manner they choose, as long as the client is informed and consents.
With an extended warranty , the warranty provider takes the role of the paying party. This gives them some influence, according the terms of the policy agreed to by the client.

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At higher speeds, when I accelerate my engine clatters. If I down-shift, and RPM comes up, the clatter goes away.

Spark knock, detonation or pinging will be worse when the load on the engine is heaviest. Shifting to a lower gear lessens the load on the engine. It is much like riding a multi-speed bicycle. The rider shifts to a lower gear to climb a hill. Even though they pedal faster (RPM), the effort required to push the pedal is much less.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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Buying spark plugs for my vehicle and noticed a much higher priced iridium plug listed. My vehicle calls for copper plugs but would the higher priced plug perform better?

Engines that use iridium plugs are designed for their use. Putting them in an engine designed for copper plugs will not show a benefit, relative to cost.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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Can a bad head gasket cause my engine to misfire?

Head gaskets fail in many different ways. If the gasket fails between a water passage and a cylinder, the coolant can enter the cylinder and cause a misfire. The problem is often worse on startup. There are also many other possible causes for a misfire and a head gasket can be blown and not cause a miss. Test are available to help confirm the problem.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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Can a bad PCV valve cause my engine to miss?

A positive crankcase ventilation or PCV valve can cause an engine misfire, especially at idle and worse when the engine is cold. If the valve sticks in the open position it will act like a vacuum leak. If the valve sticks closed it can disturb the fuel air mixture.
For far more information on PCV valves please see our Detailed Topic, Symptoms of a Bad PCV valve.

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Can a leaking valve cover cause a P0300 code?

Many engine designs have spark plug access holes designed into the valve covers. Oil leaking into these areas can deteriorate plug wires, coils and cause spark plugs to misfire, any of which can cause a P0300 code.
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Can a rusty gas tank cause the fuel pump to keep going out?

Rust in the fuel tank is a primary cause of repeat fuel pump failure. Rust will be ingested by the fuel pump and cause rapid failure. Other causes include dirty fuel and allowing the fuel tank to run low on fuel.
For more information on fuel pump failure, please see our Detailed Topic What Causes Fuel Pumps to Fail.

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Can a serpentine belt with no cracks be bad?

Excessive and deep cracks in the ribs of a serpentine is one sign of failure. Minor cracks are generally not a problem. A serpentine belt also wears out and the ribs wear away. This is hard to spot without a special gauge. Worn belts may look fine, but can slip and cause damage to belt-driven components.
For more information on belt inspection, please see our Detailed Topic, Symptoms of A Bad Serpentine Belt and EPDM Belts.

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Can changing a serpentine belt cause the timing belt to break?

Replacing a serpentine belt would not likely cause a timing belt to break. Far more likely might be if the serpentine belt was bad, the timing belt was near the same condition. All belts have a life span and will fail in time.
Please see our Detailed Topic article All About Timing Belts for far more details.

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Can I increase my fuel mileage by turning off the engine every time I stop, such as at traffic lights?

If fuel mileage were the sole concern, stopping and starting the engine may save a very small amount. Idling is inefficient and waste fuel. Miles per gallon go down, because fuel is being burned and miles are not being traveled. Starting the engine draws the battery down and wears the starter and flywheel. It may also cause slight increased fuel consumption as starting and cold operation requires fuel.

I think the answer depends on degree and consideration of overall lowest cost. With sitting for short periods, say less than a three minutes, it may be best to leave the engine running. Longer periods, say five minutes or more, may benefit from shutting off and restarting.
For more information on increasing fuel mileage, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.

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Can I put windshield washer concentrate in my vehicle without diluting it?

Windshield washer fluid is made of methanol, detergent and dye. The methanol provides freeze protection, but is also toxic and can be flammable. As with any chemical that can be hazardous, less is better. Only the amount of concentrate needed to protect the fluid from freezing in the area where operated should be used.
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Can I tell if the timing belt on a vehicle has been replaced?

Many shops place a label on the outside the timing cover, listing the date and mileage of replacement. Without such a label or a record showing the timing belt has been replaced, it is nearly impossible to determine. The timing belt is normally not readily visible and even with close inspection, it is difficult to know the condition of the belt.

See our Detailed Topic article All About Timing Belts for far more details.
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Can running my fuel tank low really damage my fuel pump?

Low fuel is a leading cause of fuel pump failure. On newer vehicles, running out of fuel one time can damage the fuel pump.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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Could a plugged catalytic converter cause a rear main seal to leak?

Driving with a plugged converter will cause back-pressure in the intake and can raise crankcase pressure significantly. This can easily result in leaking seals and gaskets through out the engine as well as several other problems.
For more information on please see our Detailed Topic, Catalytic Converters Problems.

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Do all Ford V8 engines have the two piece spark plugs that tend to break when removed?

No, only the three-valve engines came with the two piece plug and the plug was no longer used after 2008.
The two piece plug was used in the 4.6L, 5.4L and 6.8L 3-Valve engines; The two Valve engine does not use this plug.
FORD:

2005-2008 Mustang
2004-2008 F-150
2005-2008 Expedition, F-Super Duty
2006-2008 Explorer,
F-53 Motor home Chassis
2007-2008 Explorer Sport Trac

LINCOLN:

2005-2008 Navigator
2006-2008 Mark LT
MERCURY:
2006-2008 Mountaineer
more information, please see our Detailed Topic, Ford Spark Plug Breakage.

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Do cracked cylinder heads cause the radiator to over pressure?

The symptoms will depend on where the crack is. A crack in the combustion chamber normally shows up as an overheating engine. Many times there will also be a miss on engine startup. A crack into the oil gallery may show up as oil in the coolant or coolant in the oil. Other cracks may show seemingly unrelated symptoms. For instance a crack in the head bolt area may only show up as a loss of coolant with no apparent leak.
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Do I need to have the wheel bearings on my vehicle serviced?

Many newer vehicles no longer have wheel bearings that can be serviced. The move has been toward sealed bearing assemblies that do not require maintenance. There are still some vehicles that do require bearings to be packed. This is often done in conjunction with brake service. Check your maintenance manual to see when and if the bearings on your vehicle need to be packed.

Please see our Detailed Topic article Adjusting Wheel Bearings for far more details.
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Does a blown head gasket cause oil in the cylinders?

Head gaskets fail in many different ways. If the gasket fails between an oil passage and a cylinder or an oil galley and intake port, oil can enter the cylinders. There might also be other causes, such as a bad intake gasket, bad valve guide seals or bad piston rings. The head gasket might also fail and not cause such a problem, depending on the nature of the failure.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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Heavily accelerating, I accidentally shifted from fourth gear to third, instead of fifth. The engine RPM pegged out, and the engine was damaged. The dealership refuses to warranty the engine. Shouldn’t the rev limiter have prevented this?

The rev limiter will keep the engine from accelerating beyond a certain pre-set RPM, under its own power. Downshifting the transmission allows the speed of the vehicle and gear-ratio selected to determine the RPM. This is known as a mechanical over-speed and the rev limiter cannot prevent it. Over-revving the engine by any means considered abuse and not covered by vehicle warranties.
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Help! My neighbor and I were trying to change the spark plugs in my 4.6L, F150 and one of the plugs stripped in the cylinder head. Is there anything that can be done, short of pulling the head?

This is a common problem on this engine. There is a procedure that can replace the threads with a threaded insert. While the tooling is costly, many shops including AGCO have it and will make the repair for you. This makes a permanent repair and should cost substantially less than head replacement. I would suggest you have the vehicle towed to a professional and have them make the repair for you.
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How can I adjust the idle on my car?

Idle on modern vehicles is controlled entirely by the power control module or PCM, with input from several sensors. There is no adjustment possible on these vehicles. Improper idle speed indicates a problem and when the problem is corrected idle speed will return to the proper RPM.

It is also normal for idle speed to vary considerably under differing conditions. For instance the vehicle may idle quite fast before it reaches operating temperature. Slight overheating may also cause a faster than normal idle. If in doubt, you might have the vehicle checked for proper idle speed.
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How can I adjust the idle speed on my vehicle?

Idle speed is controlled by the PCM on virtually all modern vehicles and no adjustment is possible. When all inputs are correct and the engine is running properly, the idle will be correct. Improper idle speed indicates another problem that will need to be diagnosed and corrected. Improper idle speed is a symptom and not the problem.

For more information, please see our Detailed Topic idle control and throttle bodies.

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How can I tell if the intake is leaking on my GM vehicle?

The first symptom most people notice is a loss of coolant. The coolant reservoir should never be low, under normal use. A vehicle does not lose coolant unless there is a leak. Losing coolant is always a sign of a problem. Other symptoms can include a check engine light, coolant in the oil, oxygen sensor and catalytic converter failure and misfires in the engine. If the intake gaskets are not repaired, coolant can leak into the cylinders and destroy the engine.

For much more information on leaking intake gaskets see our Detailed Topic section.
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How long do spark plugs last?

The life of a spark plug depends on the design and the operating conditions. Design largely means the material from which the electrodes are constructed. For instance, copper plugs last about 30,000 miles. Platinum will last about 80,000 and iridium can last 100,000 or more, under average conditions. An engine that is running too lean or too rich or consuming oil can foul plugs in considerably less mileage, regardless of type.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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How much does it cost to change valve cover gaskets?

As with all repair, the cost depends on the complexity of the job. Due to the vast number of designs and options on those designs price will vary considerably. For instance, the upper intake manifold must be removed to replace some valve cover gaskets. Others may require removal of air conditioning, power steering or other components. On others, access is very open. Another consideration is the type of gasket used. Gasket prices can easily vary up to 400% depending on the quality of the gasket used. Another factor to consider is root cause analysis of the problem; why is the gasket leaking. This takes additional time and adds cost, but insures a more permanent repair.
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How much injector cleaner is too much?

Any injector cleaner is too much under normal conditions. Injectors are self cleaning and adding injector cleaner is not necessary or good for the system. Using a good grade of name-brand fuel is much less expensive, causes no damage and does a much better job of keeping injectors clean.
Please see our Detailed TopicFuel Injection and Wallet Flushing for more information.

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How often should I pack the wheel bearings on my vehicle?

Only a few vehicles being produced today have wheel bearings that can be packed and the rest have sealed bearing. Those that can be packed are normally serviced around 40,000 miles or at each brake service, whichever comes first.

See our Detailed Topic article Packing and Adjusting Wheel Bearings for far more details.
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How often should my fuel injectors be cleaned?

Actual cases of injectors needing cleaning are fairly rare. Far more common are injector flushes being sold. Injector flushes should be viewed with caution, if there are no symptoms. The most common symptom of a dirty injector is rough idle. Rough idle can also be caused by a great many other things and the problem should always be diagnosed, before injector cleaning is attempted.

Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.
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I always get confused when ordering parts. Is there a standard for which side is considered left or right. It seems like it depends on the way you are facing.

Many people confuse this and it might be safest to say driver side and passenger side. An experienced part person will immediately know which you are referring to. In the US, left is always the driver side, as in facing the hood from the driver seat. On transverse mounted engines, right is the side facing the windshield and left is the side facing the front bumper.
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I have a burning smell when driving my vehicle. A shop told me the valve covers were leaking but I don’t see any oil on the ground under the car.

On many engines valve cover leakage will cause oil to run onto the exhaust and produce a burning smell. Quite a bit of oil can leak before it actually begins to drip to the ground. The majority may be burned on the exhaust manifold rather than dripping.
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I have a Chevrolet Suburban with a 5.3L engine. The idle is very rough after it has been sitting overnight. After driving it smooths out until it sits for a while and it is then rough again.

The 4.8L, 5.3L and 6.0L General Motors V8 engines had a good deal of problems with intake manifold leakage. The intake allows un-metered (by the mass air flow sensor) air to enter which causes the engine to idle rough. When the engine warms, the oxygen sensors detect the situation and compensate by adding additional fuel in the form of fuel trim. This is why the engine smooths out when warm. Eventually the check engine light will come on when maximum fuel trim is reached.
For more information, please see our Detailed Topic, GM V8 Rough Idle When Cold.

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I have a fluid all over the inside of the left rear tire of my Suburban. What could be leaking in that area?

Two possible causes are, a leaking rear axle seal or a leaking rear wheel brake cylinder. Both are potentially dangerous and the vehicle should not be driven until the problem is diagnosed and corrected.

An axle seal will leak gear oil which is thick and sticky. A leaking axle seal is often the result of a bad axle bearing or a worn axle shaft. A plugged axle vent can also cause an axle seal to leak. If the oil leaks onto the rear brake shoes the will be ruined and require replacement.

A leaking rear brake cylinder will leak brake fluid, which is much thinner in consistency than gear oil. Leaking wheel cylinders must be replaced and the brake shoes may also need replacement if contaminated by the brake fluid.

Cylinders leak primarily due to corrosion. The brake fluid may have become corrosive and damaged the surface finish inside the wheel cylinder. Quality shops have meters to test brake fluid for pH and it should always be thoroughly flushed BEFORE the new cylinders are installed.

Failure to flush the fluid before replacing the cylinders may result in the contamination being forced into the new cylinders, permanently damaging them.
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I have a Ford with the two piece spark plugs. Is there anything I can do?

We have good luck removing these plugs, if the engine has 50,000 or less miles. The breakage problem gets increasingly worse with mileage. I suggest replacing them as soon as possible.
The two-piece plugs was used in the 4.6L, 5.4L and 6.8L 3-Valve engines; The two Valve engine does not use this plug.
FORD:

2005-2008 Mustang
2004-2008 F-150
2005-2008 Expedition, F-Super Duty
2006-2008 Explorer,
F-53 Motor home Chassis
2007-2008 Explorer Sport Trac

LINCOLN:

2005-2008 Navigator
2006-2008 Mark LT
MERCURY:
2006-2008 Mountaineer
For more information, please see our Detailed Topic, Ford Spark Plug Breakage.

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I have a late model Ford F150 with a 4.6L engine. There is a bad oil leak in the area of the oil filter. I have checked the filter and even replaced it and the leak is still there.

The part the oil filter bolts to on this engine is call the oil filter adaptor. There is a thick seal between the filter adaptor and the engine block that does sometimes leak. Replacing the seal is involved as the lower radiator hose also connects to the same adaptor. Draining the cooling system will be necessary. Search our category on cooling systems for tips on replacing coolant.
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I have a roaring noise when I drive. It sounds like a wheel bearing, but could be a tire. How can I tell which it is?

Chopped and out of round tires can produce a sound, almost indistinguishable from a wheel bearing. In the shop, we attach a series of microphones under the vehicle and use headphones and a rotary switch to isolate the source of the noise. Without such equipment, rotate the tires, front to rear and see if the noise moves. If it does, tires are the more likely cause. Another tip is to listen to the noise on different road surfaces. Tire noise will usually change, bearing noise will not. Finally, if it is a front wheel bearing, cutting the wheel sharply, right to left, while driving will usually change the pitch.

See our Detailed Topic article Adjusting Wheel Bearings for far more details.
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I have a very old vehicle with a carburetor and the engine is misfiring. How can I find out what is causing the problem?

A good starting point in diagnosing a misfire is to determine if you have a single cylinder or multiple cylinder problem. Without other equipment, a good way to determine this is with a vacuum gauge. Attach the gauge and note the reading. Remove the spark plug wires, one at a time, with the engine running. The vacuum should drop about the same amount when any wire is removed.
IF it does not drop on any one cylinder, that cylinder is where the misfire is occurring. Swap the spark plug and wire with one on a cylinder that is not misfiring. If the misfire moves, the plug or wire is bad. If not check the compression on the engine and see if it that cylinder is low. IF the compression is low, the problem is likely an internal engine problem.
If all cylinders make about the same difference, when the plug wires are removed, the miss is likely affecting all cylinders equally. This could be the caused by the carburetor, a bad vacuum leak, mis-routed plug wires or other things that affect all the cylinders equally.

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I have a very weird problem with an older Buick LeSabre. After sitting for about an hour, I turned the key on and there was a loud bang. The intake manifold literally exploded and is in pieces. What could cause such a thing?

General Motors has a recall on this vehicle for this problem. Defective programming can cause the ignition to fire when the key is turned on. If there is fuel vapor in the intake, such as sitting for a while after running, it can be ignited. There is an updated program for the computer that is supposed to prevent this from happening.
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I have always taken my car to the new car dealer for maintenance. For my last maintenance I went to another shop recommended by a friend. They pointed out several items that should be under warranty. Why did the dealership not point these out?

Inspection standards vary greatly from one shop to another. Some are thorough and others very lax. Another built-in problem with dealerships, is the way they often pay technicians for warranty work. Many times a dealership technician is paid much less to do warranty work than to do the same work when it is client paid. The incentive seems to be not to look very hard for warranty problems.

I feel the better solution is to find a quality independent shop to maintain the vehicle and use the dealership only for warranty-paid repairs. See our Detailed Topic article Maintaining New Vehicles for more details.
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I have an old trailer and need to replace the tires. Is there a way to know how much torque the lug nuts should have?

In cases where lug torque specifications are unknown, the diameter of the lug stud can be used as a rough guide. When using such a method, it is a good idea to re-check the torque at frequent intervals.

For more information, please see our Detailed Topic Wheel lugs, torque and keeping the wheels on.
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I have an older Chevy 1500 Pick Up with a 5.7L engine. It runs very well but the engine pings or clatters on acceleration. I have tried different grades of fuel, but it still clatters, any ideas?

Pinging or clattering on acceleration is normally caused by pre-detonation of the fuel/air mixture. This condition can be very damaging to the engine and should not go unattended. There are many possible causes ranging from carbon build up in the combustion chamber to a lean fuel/air mixture.

The exhaust gas recycle (EGR) system and the anti-knock sensor are two of the systems that deal with ping. This is a good place to begin, as both systems can be tested with proper tooling. An air flow meter, a vacuum leak, carbon build up or even clogged injectors can also cause this problem.

Low grade fuel may also add to the problem as well as causing carbon buildup and clogging injectors. I recommend using name brand fuel, from a high volume station. AGCO can test your fuel for alcohol content and quality if needed.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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I have an older vehicle which I have not maintained well. It has some problems now and I wonder if it is worth fixing?

We see quite a few vehicles in this situation. I normally recommend a full general inspection of the vehicle before deciding. With a proper inspection, you should be able to learn what is wrong and what is likely to fail soon. Beyond that it is a matter of cost relative to value. Our cost saving calculators category should be able to help.

Our Buy or Keep Calculator is designed to help you make just such a decision.
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I have an older vehicle with several oil leaks and have been told it is not practical to repair them. I don’t expect perfection, but they are really making a mess in my drive and the vehicle is great other than that. Any suggestions?

First the vehicle should be checked to make sure there is not a common cause for the leaks. Many times multiple leaks are a symptom of a malfunctioning positive crankcase ventilation (PCV) system. A manometer is used to check the efficiency of the system and it should be repaired before leak repairs are attempted.

Once the PCV system is working properly the engine should be cleaned. This makes leak detection much easier. There is a dye that can be added to the oil and with a special light and glasses, leaks can normally be readily identified.

If your main goal is to keep the drive clean, and not restore the engine perfectly, I suggest starting with the worse leaks first. Repair the most serious leaks, drive the vehicle for a couple of weeks and see if the results are satisfactory. If not, the next most serious leaks can be addressed and so on. In this manner you may find a point at which the oil leaks are satisfactorily addressed without having to repair every leak.

Many times the leaks that are most costly to repair are also very minor contributors to the problem. If you do not wish to reseal the entire engine you may find a good cost/benefit balance through the above method.
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I have had several fuel pumps fail in one year, any ideas?

Very low quality parts are common today. I recommend using an original equipment replacement pump only. In every other instance where I have found repeated and very rapid fuel pump failure, the cause has been a rusted or contaminated fuel tank. The tank should be removed, emptied, and inspected very carefully for rusting. If rust is found in the tank, replacement of the tank is the only long-term solution I have found.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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I have had to repair three of the power windows on my vehicle. Why so many problems?

Some vehicles are more prone to problems, due to design. Even on problematic vehicles, certain steps can greatly reduce the chances of problems. In the detailed Topics section there is an excellent article on, Preventing Power Window Problems.
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I hear a squeaking noise coming from the instrument panel of my Chevy Silverado. The noise stops when I switch the truck off.

One common cause of a squeak when the engine is running, is the small stepper motor in the tachometer. The 2003 through 2006 GM truck instrument panel cluster or IPC is normally under recall for up to 70,000 miles. To have it repaired under the recall, you would have to return to a GM dealership. If you are out of the recall mileage, any independent shop can make the repair for you, often at a lower cost.

See our Detailed Topic article GM Dash Gauge Failure for far more details.
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I recently bought a Ford vehicle with a key pad entry system on the door. I did not get the code when I bought the vehicle. Is there a way to find out what it is?

The entry code is stored by the vehicle computer system and most shops are equipped with tooling that can retrieve it for you.
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I recently had to have the wiring on my vehicle repaired. A rodent chewed the wires and the expense was considerable. Is there an easy way to prevent this?

Many report good success with a few moth balls in a small cloth bag and placing them in several spots under the hood. The smell seems to keep the rodents at bay, and there should be no problem if the bags are kept away from hot objects.
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I replaced my catalytic converter and twenty thousand miles later it is bad again. Why would the converter continue to fail?

The most likely case is that converter failure is the symptom being mis-diagnosed as the problem. Many things can cause a converter to fail prematurely. Common causes are bad oxygen sensors, coolant leaking into the intake, an engine running problem and improper oil being used in the engine. Catalytic converters normally last well over 100,000 miles unless there are other problems.
For more information on catalytic converters please see our Detailed Topic, Catalytic Converters Problems.

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I replaced my tires with larger sizes and now my speedometer appears to be off. Is this possible?

Speed and miles traveled are calculated. The calculation is based on the number of revolutions made by the wheel. With taller tires, the vehicle will travel farther for each revolution. This is due to the larger circumference of the tire. The calculation is based on the tire size the vehicle is supposed to have. With larger tires, the vehicle travels faster than the speedometer shows.

To see how much tire size affects speedometer error, see our online calculator.
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I suspect the catalytic converter on my vehicle is going bad, what are the normal symptoms?
Catalytic converters, like many parts, fail in several ways. The symptoms generally depend on the nature of the failure. For instance, a cracked ceramic housing may result in a rattle when running. A failed catalyst will normally set a check engine light on a post 1996 vehicle.

Catalytic converters sometime also plug up or restrict the exhaust. Some possible symptoms of a plugged catalytic converter include:
- A lack of engine power
- An overheating engine
- Failure to start
- A rotten egg type of odor
- Reduced fuel mileage
- A change in exhaust sound
A good way to isolate a plugged converter is with an exhaust back-pressure test. A pressure gauge is tapped into the exhaust, ahead of the converter and the pressure measured. Pressure is then measured after the converter. This step eliminates a plugged muffler as a possible cause. Pressure before the converter above three PSI at 2,000 RPM and pressure after the converter below this figure show a plugged converter.
For more information on catalytic converters please see our Detailed Topic, Catalytic Converters Problems.
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I was rotating my tires and when I tried to remove the wheel, one of the lug studs stripped. I questioned the shop that installed the tires (6,000 miles before) and they said I stripped the stud. What is your opinion?

It is unlikely a lug stud could be stripped removing the nut. Fasteners are stripped by improperly threading them together or by over-torque. I would discuss it further with the service manager of the shop.
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I was told the rear main seal on my engine is leaking. Why does it cost so much to repair?

The rear main seal is located between the engine and transmission. One or the other will normally need to be removed in order to replace the seal. Because of the amount of time required, this is normally an expensive repair.
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If I accelerate without downshifting my engine clatters. If I down-shift, and RPM comes up, the clatter goes away.

Spark knock, detonation or pinging will be worse when the load on the engine is heaviest. Shifting to a lower gear lessens the load on the engine. It is much like riding a multi-speed bicycle. The rider shifts to a lower gear to climb a hill. Even though they pedal faster (RPM), the effort required to push the pedal is much less.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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If the accelerator on a vehicle sticks, what is the best thing to do?

Shifting the vehicle to neutral should keep it from accelerating and maintain engine power to run the power steering and power brakes. If this is not possible, turning off the key or pushing and holding the stop button should stop the engine. The brakes should also stop the vehicle, although it may take much longer than normal and require much harder application.
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In what order are cylinders of an engine numbered?

Each manufacturer assigns their own sequence and this even varies among different engines from the same manufacturer. On current domestic V-8 engines, GM and Chrysler normally starts on the left (driver) side and place odd number on the left and even numbers on the right.

Ford more often starts on the right (passenger) side and proceeds in numeric order on their V-8 engines.

V-6 motors often emulate the V-8, made by the same manufacturer, omitting the two rear cylinders. For instance GM and Chrysler start with one on the left and place odd numbers on left and even on right. Ford often starts on the right and numbers the same as their V-8 engines. Other Ford engines, like the Probe 2.5L and Villager 3.0L and 3.3L, start on the right but place odd numbers on the right and even on the left. Because of the tremendous variation, we always consult service data for each individual engine.
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Is a valve cover gasket and a head gasket the same thing?

A valve cover gasket seals the valve cover , normally on top of the cylinder head. A head gasket seals the cylinder head to the engine block and is beneath the cylinder head.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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Is it better to allow an engine to idle while waiting in line or stop and start the vehicle? How much sludge in the engine is caused by idling and how much wear does turning the car on and off again create?

Idling is inefficient and waste fuel. Sludge buildup is not so much of a concern, as long as running hours are considered, regarding oil changes and not just miles. Starting the engine draws the battery down and wears the starter and flywheel. It may also cause slight increased fuel consumption as starting and cold operation requires fuel.

I think the answer depends on degree. With sitting for short periods, say less than a three minutes, it may be best to leave the engine running. Longer periods, say five minutes or more, may benefit from shutting off and restarting.
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Is it helpful to power wash an engine?

Power washing an engine can force water into electrical connections and sensors and can cause a great deal of problems. Far better would be to use a pair of gloves, brush, solvent and rags to carefully wipe each area clean.
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Is it possible to have a blown head gasket if I have never over heated my engine?

Overheating is a leading cause of head gasket failure, but not the only cause. A few of the other things might be, a severely neglected cooling system. Coolant with pH below 7 can cause corrosion and cause head gaskets to deteriorate. Poor machine work finishes, on cylinder heads and engine blocks can also result in failure. Engine detonation or pinging greatly increases combustion chamber pressure and can also cause head gaskets to fail.
For more information on valve clatter, please see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.

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Is it true that continuing to drive with a bad catalytic converter can damage my exhaust system?

Driving with a bad catalytic converter can cause all sorts of problems to the engine as well as the exhaust. High back-pressure can damage exhaust manifolds and manifold gaskets. Another common problem is when material from a failing converter is blown into the muffler. At best this can cause an annoying rattle. At worse the muffler will also be ruined.
For more information on catalytic converters please see our Detailed Topic, Catalytic Converters Problems.

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Is there a lubricant that will help valve clatter on acceleration?

Valve clatter, also known as detonation, spark knock, etc. is not a lubrication issue. It occurs when fuel spontaneously ignites, before the ignition spark fires. This results in the combustion explosion occurring prematurely, as the piston is still trying to travel upward. This also vastly increases combustion chamber pressure and temperature and can cause serious damage very quickly. No lubricant can help, rather the cause(s) must be diagnosed and corrected.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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Is there a simple test for a broken timing belt?

On many vehicles, removing the oil filler cap will allow the camshaft to be seen. If so, crank the engine and see if the camshaft is turning. If not, the timing belt is likely broken or stripped. Of course this cannot reveal an engine that is out of time due to a slipped timing belt that is still attached.

For more details on timing belts, check the AGCO Automotive article All About Timing Belts.
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Is there a simple test to check a power window motor?

The most basic test is to check for power and ground, at the motor. This is done with a DC volt meter. One lead is attached to each of the motor terminals. When the switch is pushed, there should be full battery voltage present. If so, and the motor does not run, the motor is very likely the fault. If there is no voltage with the switch pushed, the problem is electrical, such as a blown fuse, bad relay, bad switch or possibly a burned connection..

On many modern vehicles there may be several wires at the motor. A wiring diagram is needed to determine which wires are supposed to be power and which are ground wires. These type motors sometimes require a scan tool to test properly.

Burned connections, switches and motors often result from excessive drag on the windows. For information on preventing power window problems, see out Detailed Topics section for the article Preventing Power Window Problems.
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Is there an additive that will stop a rear main seal leak?

Unfortunately not. Seals usually leak because of excess pressure, sealing surface movement or because the seal has gotten hard. The most common cause of seals getting hard is not frequent enough oil change intervals. Additives claim to work by swelling seals. This normally has the affect of breaking down the rubber and making not only this, but all seals in the engine far worse. A proper repair will not only be effective, it will be far less expensive in the long run.

A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.
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Is there an easy way to check the accuracy of my speedometer?

Most U.S. interstate highways have mile markers. Have someone with a watch, equipped with a second hand check the time between the markers as you hold your speed at exactly 60 MPH. It should take one minute from one mile marker to the next and five minutes to pass five. If not your speedometer is reading too slow if you pass them quicker than 60 seconds and too fast if it takes over 60 seconds.

For more on how tire size affects speedometer error, see our online calculator.
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My battery cables keep getting corroded. I clean them and a few months later they are corroded again.

Battery cable corrosion comes from acid leaking around the battery terminals. When the acid leaks onto the metal terminals, corrosion is the result. Cleaning the terminal is only treating the symptom. Leaking terminals are considered a defect in a battery. The battery should be replaced under warranty, if there is one in force. If not, a battery is far less expensive than damage that can be done by leaking acid.
For more information, please see our Detailed Topic The Cost of Battery Corrosion.

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My car broke down out of town. Upon inspection several things have obviously not been maintained and could have been done under warranty. The vehicle was regularly serviced by the dealership. How can I find quality service?

The level of quality a shop provides, is a matter of the way it is operated. Some dealerships may offer good service, other dealerships very poor. The same is true of independent shops.

New car dealerships provide warranty service for the manufacturer. You have paid for warranty service, in advance. The cost of the new car warranty was included in the price of the vehicle when you bought it. Dealerships should be used to provide warranty service.

An independent shop may be a better choice to provide maintenance and advice on items covered by warranty. In this way, the independent shop can verify that the warranty work was performed properly.

For much more information on finding a high quality shop see our Detailed Topics Articles:

Finding a Great Auto Repair Shop and

How Do You Find Quality.
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My car idles rough when it is cold. I had a tuneup done but the idle is still the same. The shop now says there is a leak at the intake. Did I get ripped off?

Asking for a specific service is NOT the same as giving a symptom and asking for a diagnosis of the problem. If you requested a tuneup, you diagnosed the problem yourself and the shop simply gave you what you asked for. The vehicle may well have needed a tuneup, it simply was not the cause of the rough idle. If the vehicle was driven in that day, likely it was fully warmed up when the shop saw it. If the rough idle when cold was not mentioned, they have no way to know it existed.

Better shops do not generally promote menu items such as tune-up or brake job. Rather they ask for the symptom you are experiencing; What you would like to see fixed. Given the symptoms, a qualified shop will suggest the proper course of action. Such an approach may have prevented your poor experience.

For much more information on getting better service and saving money, see our Detailed Topics article Save Money and Get Far Better Repair.
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My car keeps eating distributor caps. It misses under acceleration and when I change the cap it quits missing for 500 miles, then the misfire returns. Why would the caps keep going bad?

Very likely the caps are not going bad. When replacing the cap, several wires, and the distributor, are moved around. Likely, something in the act of replacing the cap is temporarily changing the problem. Check all wiring for loose terminals and check the distributor magnet for cracks.
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My car was hit from behind. Driving home after the accident, the car died. I am told the timing belt broke. Could this happen in the accident?

Unless the vehicle was hit hard enough to shift the engine and break the timing cover, it is very unlikely to cause a timing belt to break. If the belt is more than seven years old or past the recommended replacement mileage it is far more likely it broke for those reasons.
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My car will not start. It has fuel pressure and I have changed the spark plugs, distributor cap and rotor, plug wires and coil. I towed it to a shop and they replaced the fuel pump. How can that be if it had fuel pressure?

In order to start and run a vehicle must not only have fuel pressure, but have the correct amount of pressure. A very accurate gauge is needed. Lacking only five PSI will sometimes mean the difference between running fine and not starting. A second issue could be lack of fuel volume. It is possible to produce adequate pressure without enough volume to run.
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My engine feels like it is not getting gas. Could this be the fuel pump?

The term, "feels like," is a very expensive way to repair a vehicle. It is virtually impossible for even a highly trained technician to determine a problem by the way the vehicle feels. Instead a fuel pressure test should be performed. If the fuel pressure or volume are below specifications, when the problem is occurring the fuel system would be suspect. Further testing would be needed to isolate the fuel pump as the cause. A bad fuel pressure regulator, clogged fuel filter and even a power control module or wiring could account for improper fuel delivery. If fuel pressure test does not show a problem, checking other systems such as ignition, compression, vacuum and so on would be in order.

For more information, on Engine Diagnostics see the AGCO category, under Services.
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My engine has over 100,000 miles. Should I replace the timing chain?

Most modern engine have lubricated timing chains and many are roller type design. Using the proper oil and a good oil filter, the timing chain may last the life of the engine.
For more information on the proper oil and filters, please see our Detailed Topic The Sad Truth (about extended oil changes).

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My engine is leaking oil at the valve covers. Is this a problem?

Oil leaks are often a symptom of poor vehicle maintenance. For instance, not replacing engine oil often enough will cause seals to get hard and gaskets to crack and leak. A plugged PCV system will allow pressure to build and cause many leaks. The largest concern with oil leaks are damage to rubber suspension components and hoses. Oil from leaks can dissolve many rubber components and create large repair bills. Many people also complain of a burning odor with valve cover leaks. Valve covers are often above the hot exhaust system. Leaking oil burns on the exhaust system and can create quite an odor.
For far more information on PCV valves please see our Detailed Topic, Symptoms of a Bad PCV valve.

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My engine size is listed as 3.0L, what is the equivalent size in cubic inches?

Liters are a metric expression of engine displacement. The volume of all cylinders equal three liters. The cubic inch displacement would be about 183 cubic inches. You can use this calculator to convert liters to cubic inches on other engines you may be interested in.
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My engine's valve covers are leaking and I was quoted several hundred dollars for the repair. A friend told me the valve cover gasket on his vehicle cost less than 100 dollars to replace. Does such a price difference sound right?

Engine design and valve cover placement varies considerably from one engine to another. Some are right on top of the engine and very easy to replace. Others require substantial disassembly of the engine to replace. For instance, many require removal of the upper intake manifold for access. Price is normally based on time required to accomplish the job and will vary considerably.
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My GMC Sierra has a cracked cylinder head and loses coolant. Is it safe to drive as long as I maintain the coolant level?

The GM Silverado, Sierra, Tahoe, Suburban, Avalanche and other vehicles that use the 5.3L and 4.8L engine, have a known problem with cylinder head cracking. Unfortunately the crack tends to leak coolant into the engine oil. Coolant quickly destroys the oil's ability to protect the engine and severe damage will result from continued driving. There are usually no outward signs other than coolant loss. Glycol combines with the engine oil and normally there will be no milky appearance.

For more information, please see our Detailed Topic GM Coolant Loss with No Apparent Leak.
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My mechanic says I should let my engine warm up before driving. Is this right and for how long?

Yes, but long warm up periods are unnecessary, because of the viscosity and computer control of the engine. Cold engines will idle at a speed, much higher than an engine that is fully warmed up. Within a few seconds, engine idle will return to normal, and then it is safe to put the vehicle into gear. Pulling a vehicle into gear, with it racing at high idle can cause damage. Normally, 10 to 30 seconds is sufficient or when idle drops below 800 RPM.
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My older Dodge Neon has a large puddle of coolant under the engine and will not start, any ideas?

The timing belt drives the water pump on this engine. If the water pump seizes the timing belt may break or be thrown off. This would account for the coolant leak and the lack of starting. Remove the oil filler cap and see if the camshaft is visible. If so, crank the engine, and see if the camshaft rotates. If it does not, chances are the timing belt has come off or is broken.
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My timing belt was replaced and now I have a squeak noise. Could the belt be loose and slipping?

It is not likely for a timing belt to slip as it has teeth that mesh with teeth in the driven sprockets.

If the teeth come off the belt, it could technically slip, but the engine would also be out of time and likely quit running. More likely the noise is caused by an idler pulley, engine accessory or possibly an accessory drive belt. Best is to bring the problem to the attention of the shop. For help with addressing problems with a shop, please read our Detailed Topic, When Things Go Wrong.
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My Toyota 2.4L engine has a timing chain. At what mileage should I consider replacing it?

Timing chains are normally internally lubricated and often last the life of the vehicle. They do not require service, unless a problem, such as noise, should arise. Using the proper oil viscosity and oil filter is critical on such engines. With the proper oil and filter it is unlikely the timing chain will ever need replacement.
For more information, please see our Detailed Topics section under Oil Viscosity.

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My truck intermittently stops running. A friend suggested I should replace the fuel pump.

Replacing parts and hoping to fix a problem can be an extremely expensive and frustrating experience. The reason for diagnosis is that it is much less expensive than part replacement. For instance, a fuel pressure gauge can tell if the problem is fuel related or not. If the fuel pressure drops off, when the problem occurs, you know fuel pressure is a factor. This still does not mean the pump is bad, as a loss of power or ground to the pump could cause the same symptom. This would require further testing.

If the fuel pressure remains adequate when the problem occurs, the fuel system is likely not a contributing factor. In such a case, the ignition, command for the injectors, inputs to the power control module, etc. might be tested.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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My vehicle has 100,000 miles. I think the spark plugs should be replaced but my mechanic says, if it is running good, leave it alone. Should I replace them or not?

I agree with you. Even badly worn spark plugs often show no performance problems. Computerized ignition systems can compensate for plug wear. The problem is the additional loading of the ignition system can produce problems that far exceed the price of the spark plugs. Where possible I prefer to prevent problems, rather than treat them after they occur.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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My vehicle has a major oil leak and I was told it was the head gasket. The car is not overheating and I am losing no coolant. How could this be a head gasket problem?

Head gaskets fail in several ways and depending on how and where they fail, the symptoms will vary. It is very possible for a head gasket to leak oil and have no cooling system problems. Only when the gasket leaks from or into the cooling system will coolant loss and overheating be a problem.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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My vehicle is leaking a clear oily fluid just behind the left front wheel. Today it also started making a gurgling noise when I turn the steering wheel. Should I quit driving the vehicle?

The combination of symptoms sounds like a possible power steering leak. It would be better to have the vehicle towed to a shop than risk driving it. Power steering fluid is flammable and can catch fire. The power steering pump can also be damaged by driving low on fluid adding considerable cost to the repair.
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My vehicle is slightly (5,000 miles) out of warranty and I discovered a problem. Is there anything I can do?

A warranty is a contract, paid for in advance. It is part of the new vehicle price. As with any contract, there is no obligation beyond the specified terms. Most dealerships have the authority to extend the warranty, within reason. Largely this is at their discretion. This may also be predicated on their thought that they may be able to retain the customer as a future vehicle purchaser. Politely asking for an extension will normally get better results than demands.

A good way to avoid such a problem is to use a good independent shop for maintenance, rather than a dealership. A good shop can advise you of common problems and things that appear to be covered by warranty.

Another excellent idea is to have a Pre-warranty Expiration Inspection, before your warranty ends. This service, developed by AGCO Automotive, can advise you of pending problem and pattern failures as well as technical service bulletins and recalls for your vehicle. For more information, on a Pre-warranty Expiration Inspection, see the AGCO category, under Services.
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My vehicle is ten years old and has 50,000 miles. I was told I should replace the timing belt. The book says 90,000 miles, is this just a ripoff?

The person who told you this is correct. Timing belts have an age as well as mileage recommendation. Most manufacturers recommend timing belt replacement at or before seven years.

For more details on timing belts, check the AGCO Automotive article All About Timing Belts.
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My vehicle is two years old but has 43,000 miles. The manufacturer's warranty was for 3 years or 36,000 miles. I am having an expensive problem and wonder if there is anything that can be done under warranty?

The answer depends on several factors. One would be, if the problem was brought to the dealer's attention during the warranty period and not repaired. Many manufacturer's recognize this as an on-going problem and will extend the warranty somewhat.

Another option would be if the part(s) that have failed or covered under a policy adjustment or not. Sometimes when a manufacturer has a known problem with a product, they will offer repair at no or greatly reduced cost for that item. They may NOT offer this information and you should always ask.

Certain parts are also covered longer than the stated warranty. For instance the engine computer and catalytic converter are often covered by the EPA mandated eight year/80,000 mile emissions warranty.

A polite inquiry will sometimes get results. You may also get results by calling the toll-free number in your owner's manual, even though the dealer has refused to help.
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My vehicle is using a lot of oil but there is no leak or smoke from the tail pipe.

Modern vehicles use catalytic converters and will rarely smoke, even with considerable oil consumption. The heat of the converter will vaporize the oil and thus no smoke. Unfortunately, continued oil entering the converter will likely destroy it, due to excess heat. This will add considerable expense to the problem. Best is to have the vehicle checked and rectify the source of the oil consumption.
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My vehicle over heated and I suspect the head gasket is blown, can this be tested?

A simple test for carbon dioxide in the coolant helps detect a blown head gasket or cracked cylinder head. This is not foolproof but is a good indicator. Should this test prove positive a more extensive test can be run to isolate the cylinder(s) involved.

In the more involved test all spark plugs are removed. A very sensitive pressure gauge is attached to the cooling system. One plug is installed and the engine cranked over. If the pressure starts to rise, that cylinder is open to the cooling system. The test is then repeated for each cylinder. Lastly a thorough inspection must be done to isolate leaks into the oil or to the outside of the engine.

Determining a blown head gasket from a cracked head would require removal of the cylinder head. Both will exhibit the same symptoms and test results. Many shops will quote prices with and without head replacement before disassembly to cover this possibility.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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My vehicle power steering fluid comes pouring out of the reservoir. When this happens the pump gets noisy and I loose power assist. Adding fluid helps until it happens again.

Fluid being pushed out of a power steering reservoir almost always indicates air entering the system. Air is drawn in, passed a bad seal or hose and compressed by the hydraulic pump pressure. When the engine is turned off, the compressed air expands and pushes the fluid out. Low fluid level then accounts for the noise and lack of power assist.

Finding such a leak can be surprisingly difficult as many times there will be no fluid leakage. Common areas that cause such problems are the shaft seal on the pump and the return hose.
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My vehicle runs fine in normal driving. When accelerating heavily or trying to climb a hill it lacks power and will start to miss?

Lack of power and miss on acceleration is often a sign of lower than normal fuel pressure or volume. The simplest problem would be a restricted fuel filter. A weak fuel pump or bad fuel pressure regulator will also cause the same symptoms. Test driving with a fuel pressure gauge attached will indicate if this is the problem.

Restricted exhaust, from a plugged catalytic converter or muffler can also cause a similar symptom. Testing the exhaust back pressure is the best way to determine if a restriction exist.
For more information on catalytic converters please see our Detailed Topic, Catalytic Converters Problems.

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My vehicle runs rough at idle. I have changed the spark plugs, checked all coils, checked for vacuum leaks and had the injectors replaced. What else could cause a misfire at idle?

If all previous work was done correctly, I would check the engine compression. Low compression in one or more cylinders can cause a misfire. Also on overhead cam, dual bank engines, a broken chain guide, slipped or mis-installed timing belt can cause the same type issue.
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My vehicle runs very well but occasionally is hard to start. Could this be a dirty fuel filter?

A dirty fuel filter would be very unlikely as the cause, without other symptoms. A dirty fuel filter can restrict fuel flow. This can cause misfires under load, due to inadequate fuel pressure. If the vehicle runs well under acceleration, odds are fuel pressure is more than adequate to start. More likely causes would be a bad fuel pump or fuel pressure regulator. These can be easily diagnosed with a fuel pressure test.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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My vehicle will not start and there is no fuel pressure. I replaced the fuel pump but still have no fuel pressure. Could it be a bad fuel pump?

Checking fuel pressure was a wise first step, however an incomplete test. You should also verify if there is power and ground available at the fuel pump. If power and ground are available, there is still no pressure and there is fuel in the tank, bench test the old pump to see if it was actually bad. If so, it is possible you have a defective pump. Again bench test the replacement pump.

If there is no power or ground, even a new pump will not run. A wiring diagram is needed to isolate such a problem. Next go the other end of the circuit. If power and ground are present, go to the middle. Such an approach effectively eliminates half of the circuit. If power and ground are available at the mid-point, the problem lies from there to the end. If not the problem lies from the middle of the circuit to the beginning. By continuing to check in this manner the problem can normally be quickly located.
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My windshield washer pump has gone out twice in four years, any ideas?

A common cause of washer pump failure is use of water, rather than washer solution. Water will eventually develop bacteria and solids that can clog and jamb the pump. Water also freezes at 32 degrees Fahrenheit. Freezing will quickly damage the pump. Finally a dirty reservoir will allow trash to enter the pump. Cleaning the reservoir and using a quality brand washer fluid, in the proper concentration should help a great deal.
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My windshield washers froze and damaged the pump. I thought washer fluid should keep this from happening.

Washer fluid is mixed in many different concentrations. In warmer areas of the Country it may contain 90 percent or more water. When traveling to colder climates or when cold weather strikes, it can freeze and damage the system. Best is to read the label closely before using or have the fluid tested if there is any doubt.
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On hard acceleration my vehicle suffers from valve clatter, any ideas?

Valve clatter, also known as spark knock, ping and detonation, can be caused by several things. The fuel/air mixture is igniting too soon relative to the piston position. When this happens the resulting explosion is trying to force the piston down while the crankshaft and momentum or forcing it up. In time engine damage can occur.

Octane in fuel helps to prevent the condition by slowing the burning process. On the engine, the knock sensor and EGR valve are two systems charged with preventing valve clatter. A malfunction of either system will make it much worse.

Also a lean [not enough fuel relative to air] fuel mixture will cause the condition. This can be the result of a vacuum leak or a faulty air flow meter, among other things. Ignition crossfire, caused by mis-routed spark plug wires are another cause. Finally excess carbon accumulation as well as other things can create the problem.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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Recently I replaced my windshield and the glass company said I should replace my wiper blades. I have never heard of this before.

Old wiper blades can become hard and have imbedded abrasive particles lodged in the rubber. Replacing them can help protect the new windshield and will also help with viability. Wiper blades are inexpensive, I think it would be a wise investment.
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Should I carry full coverage insurance on my four-year old car or just liability?

The answer depends a lot on your financial situation. If you cannot afford to lose the value of your vehicle, insurance provides some security. Also if the vehicle is financed, insurance may be required. Insurance is simply a means of spreading risk. Drivers who do not make claims subsidize those that do. On average you will pay more than you gain and that is how the insurance company profits. I feel a safe driver, that can financially tolerate the loss of a vehicle, can profit by carrying only liability insurance.
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Should I expect better mileage or performance after replacing my timing belt?

Timing belts are replaced because they age and will eventually break. There will be no decrease in performance or mileage as long as they do not break. Replacing the timing belt will not affect performance or mileage but will prevent breakage and the possible loss of the engine.
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The battery was replaced in my Silverado and now the engine idles very low and almost dies when I turn on the AC.

When the battery is disconnected, the PCM loses idle memory. It can relearn, if the throttle body is clean. If the throttle body is dirty, it may not relearn. Try cleaning the throttle body and disconnect the battery again. When finished let it idle two minutes in park, without the AC on. Next turn the AC on and let it idle for two minutes. Lastly, put it in gear, with your foot on the brake for two minutes. It should relearn and be fine. Here's more information on idle memory.

For more information, please see our Detailed Topic idle control and throttle bodies.

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The driver's window on my car will go down, but comes up very slowly and stops about half way up. After a while it will slowly go the rest of the way up.

Slow up-travel and stopping are often the sign of a weak window motor. The weight of the glass helps the down travel, but moving up requires lifting this weight. Sometimes, cleaning and lubricating the tracks with a silicon spray will help for a while. Normally, the motor fails completely in time.

For information on preventing power window problems, see out Detailed Topics section for the article Preventing Power Window Problems.
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The engine in my car looks dirty. Is it okay to pressure wash the engine?

Pressure washing an engine is not advisable. Doing so can cause far more problems than will be cured. There are a multitude of sensors and connectors that water can enter. Water can cause these parts to short-out and become damaged.

A better method might be to simply wipe the areas clean. With a pair of protective gloves and a solvent dampened towel, the engine can be cleaned pretty well. This should never be attempted unless the engine is completely cooled. Any remaining residue can be cleaned with a mild de-greaser.
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The engine in my car uses aluminum cylinder heads. A mechanic told me I should take the spark plugs out and put anti-seize on the threads to prevent them from sticking.

Anti-seize may work as a lubricant and thus change the torque requirement of the spark plug. The published specification is for dry torque and lubricating the treads will result in much greater force at the specified torque. The anti-seize could also serve to insulate the threads and effect the heat range of the plug. A better plan might be to replace the spark plugs at the suggested interval, or sooner. Also be certain the engine is cool to the touch before replacing and use a torque wrench to tighten the spark plugs.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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The floor on the right side of my vehicle gets wet when I drive. At first I thought the window might be leaking but it happens even when it is not raining. Do you have any ideas?

Drive the vehicle for several miles and then touch the floor to see if the wet mat is warm or cool. If the mat is warm and sticky feeling, the most likely cause is a leaking heater core. The heater core is a tiny radiator and engine coolant flows through it to provide heat in the vehicle. If it leaks, the coolant will find it’s way to the floor, whether the heater is operated or not.

If the wetness feels cool and not sticky, like clean water, the most likely cause is the air conditioner evaporator core. This core is cold and removes humidity from the passenger compartment when the air conditioner is operated. There is a tray that captures the water and routes it outside where it drips harmlessly under the vehicle. If the tray becomes damaged or if the drain plugs, water enters the passenger compartment.

In either case it is important to act quickly. Once the repair is made the carpet should be removed, cleaned and allowed to dry thoroughly. Failure to dry the carpeting will result in mildew and a very foul odor that is almost impossible to remove.
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The headlights on my car have turned yellow with age. Can this be repaired without replacing the light assemblies?

There are several cleaners on the market that can greatly improve yellowed headlamps. Best results are obtained with the use of a power buffer but even hand polishing works pretty well. For a better explanation, see our Detailed Topic Dull Yellow Headlamps.
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The intake manifold was replaced on my 3.8L GM engine. Several months later the catalytic converter failed. Now I am told there is a hole in the new intake manifold, what’s going on?

Intake manifold leakage on GM engines is a well documented problem. Often when the intake fails, coolant is ingested by the engine. This can greatly shorten the life of the catalytic converter. If the converter becomes restricted, exhaust will often back up through the exhaust gas recycle (EGR) port, into the intake manifold. The hot exhaust gas can quickly burn a hole in the plastic intake, especially on hard acceleration.
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The oil level in my vehicle rises about one quart per month, what could cause this?

Two possible causes would be coolant or fuel leaking into the oil. Either is detrimental to the engine as they destroy the ability of the oil to lubricate. If it is coolant, the intake manifold, head gaskets or a cracked cylinder head are likely causes. You may also note a loss of coolant in the coolant reservoir.
Fuel may enter the engine oil due to a stuck or leaking injector. A leaking fuel pressure regulator is another possibility, on some models.

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The oil pan drain plug on my car has a strange star shaped opening. What is this called and what type tool is needed to remove it?

The internal six-sided drive is known as Torx. The tool is called a Torx bit and comes in sizes ranging from T-1 to T-60. The larger the number, the larger the bit size. These are widely used in automotive applications. Torx also comes in an inverted, tamper resistant and plus size varieties, in each size.

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The oil pressure light in my 3.0L Toyota has started to come on at an idle. When the engine speed is raised it goes out. I replaced the oil pressure sender but the light still comes on.

Low oil pressure can be a sign of worn engine bearings and worse. Sometimes, the oil pump pressure regulator can also stick. When this happens oil pressure will drop. Removing the sub-pan is easy on this engine. That would give an opportunity to inspect the bearings and access the bypass. If the bearings are okay, try removing the spring and plunger. Clean both as well as the bore the plunger fits in. Reassemble and see if the problem goes away. If not, you may be in for major repair in the future.
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The power window motors on my car have gotten sluggish. I cleaned and lubricated the tracks with silicon as you suggest in your Detailed Topic. Why do power window motors get slow and can I rebuild them?

As the motor gets older, the brushes and the bushings that support the armature wear. When this happens they loose power and become slow. Replacement is normally the best option as it is all but impossible to find parts to rebuild them.
For more information on preventing power window problems, please see our Detailed Topic Preventing Power Window Problems.

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The serpentine belt on my Chevy Astro van keeps breaking. I have replaced it twice in two years and thirty thousand miles, isn’t this too often?

Serpentine belts are normally good for 50,000 or more miles or six years. The belt should not break during that period. Belt breakage is almost always a symptom of misalignment, a wrong belt, wrong pulley or pulley damage.

If any component has been replaced on the engine, such as an alternator, AC compressor or water pump, start with that. Parts not properly mounted to the engine, such as an AC compressor, can cause the belt to be misalignment. Sight down the belt and make sure everything is in a straight line. If not, you must determine the cause and correct it.

Serpentine belts have a specific number of groves which correspond to grooves in the pulley. For instance, if the belt has five grooves and a six groove pulley is installed, it will quickly destroy the belt. Sometimes replacement parts, like an alternator, may come with the wrong pulley. This may be inadvertently installed and problems will follow.

Improper alignment can also result from loose, wrong and worn parts. A worn idler pulley or belt tensioner, can cause wear and misalignment. An improper belt for the application is another source of problems. I have always had the best luck with original equipment manufacturer (OEM) belts. Ordering from the OEM and specifying the vehicle identification number (VIN) provides a good chance of getting an exact replacement.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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The serpentine belt on my vehicle keeps fraying and breaking.

Fraying of a serpentine belt can almost always be traced to the condition or alignment of the pulleys in the system. A bent or dented pulley is a common cause. A small dent in a pulley will cut the edge of the belt as it passes. Misalignment of pulleys is common when components are replaced. For instance an alternator or air conditioner compressor. If a pulley is out of line the belt will quickly be destroyed.

Another problem, when components are replaced, is a mismatched pulley. Serpentine belts may have several different configurations. For instance, one belt may have the five-grooves and another six. Placing a six-groove pulley in a system that uses five grooves, will continually damage belts. This may happen when two options were available and the improper part is installed.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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The shifter on my Ford Crown Vic wont move out of park.

Many times this is the shift/brake interlock not releasing. This interlock is a safety feature that prevents the vehicle from being shifted out of park without the brake applied. Have someone press the brake pedal and see if the vehicle has brake lights. If not, the bulbs could be burned out or the brake light switch may be bad.

In an emergency the shifter may be able to be taken out of park as follows. Turn the ignition to the position between lock and on, but don’t start the vehicle. The shifter should now be able to be moved to neutral. Once in neutral, the vehicle can be started and the shifter moved to drive or reverse.

This will allow the vehicle to be moved, but extreme caution is in order. You must have your foot on the brakes before shifting into gear, for obvious reasons. You should also never drive a vehicle without brake lamps.
For more information, please see our Detailed Topic, How To Release A Shifter Stuck In Park.

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The speedometer on my Chevy Silverado reads very erratically? Sometimes it will read over 100 MPH when I am driving 30 MPH.

The 2003 through 2006 GM truck instrument panel cluster (IPC) used defective stepper motors. These vehicles are normally under recall for up to 70,000 miles. To have the problem repaired under the recall, the vehicle has to return to a GM dealership. If the vehicle is out of the recall mileage, any independent shop can make the repair for you, often at a lower cost.

See our Detailed Topic article GM Dash Gauge Failure for far more details.
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The steering wheel in my vehicle shakes when stopped with the transmission in gear and the brakes on?

When sitting at idle and in gear the engine is under load. A rough idle will be most noticeable under these conditions. This will be far more pronounced if the engine mounts are bad. Good engine mounts can absorb engine vibration. Worn or torn mounts can allow the engine to shake the chassis and the steering wheel. If the engine is idling excessively rough, vibration may be felt even with good mounts. A vacuum leak, bad idle control motor, plugged injectors or several other things can cause an excessively rough idle.
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The timing belt on my car broke. I towed it to the shop and they say I may have engine damage, but they wont know until a new belt is installed.

A broken timing belt often means the valves hit the pistons, causing great damage. The best test to determine this is a compression test. Unfortunately this cannot be done without installing a timing belt and putting the engine in-time. An alternative might be tearing the engine down, but this would likely be far more expensive. In such a situation, picking a shop that you trust is perhaps the best solution.

For more details on timing belts, check the AGCO Automotive article All About Timing Belts.
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The timing belt on my car was replaced at 90,000 miles. At 120,000 miles the water pump seized, broke the timing belt and ruined the engine. Should the water pump have been replaced with the timing belt?

Each repair shop and each client makes that decision whenever repair is performed. I think, it is foolish to replace a timing belt and not replace all other wearing parts in the area. I feel the cost is far less than the risk assumed. Many shops market their services on price alone. Since few clients realize the nature and extent of the risk, it is easy to make it appear as though the shop is saving them money. This is true of most service. Failing to add the cost of risk assumed into the price can be very expensive.

See our Detailed Topic article All About Timing Belts for far more details.
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There is a gauge on my dash that says RPM. What does this indicate?

RPM stands for revolutions per minute and indicates engine speed. This is the speed at which the engine is running. This gauge will rise and fall as the vehicle picks up speed and the transmission shifts gears. As a general rule, lower RPM means better fuel mileage. Also, learning the normal relationship between RPM and vehicle speed can provide a valuable diagnostic tool. If the relationship changes, for instance higher RPM for a certain speed, a pending problem is indicated.
For more information, please see our Detailed Topic, What Do Dash Gauges Mean.

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There is a whirring noise in my engine that increases with engine RPM. I suspect the alternator is the cause. Is there a simple test?

There are a few things that can give you a better chance of being correct. A stethoscope can be used to listen to each suspected area, partially blocking the background noise. A piece of heater hose can also work if you do not have a stethoscope. Temporarily removing the belt(s) and starting the engine is another method. If the noise is gone, you know the source is an accessory driven by the belt. Of course the engine should not be run more than a few seconds without the belt(s).

Spinning the pulley on each suspected component by hand can also help reveal the culprit. Noise, roughness or slack can all indicate a problem. Common sources of noise are alternators, water pumps, idler and tensioner pulleys. Also inspect the belt(s) themselves. A bad spot on a belt can cause a very similar noise.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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There is an oil leak on my Honda and the mechanic says it comes from the balance shaft seal. He suggested replacing the timing belt, balance belt and water as well as several other seals. Does this sound like a ripoff if the other parts are okay?

If the vehicle has seventy thousand or more miles and the timing belt has not been replaced, this might be a prudent recommendation. When replacing the balance shaft seal, the other parts mentioned would be very accessible, greatly lowering the cost of their replacement. Not replacing them could result in having to dissemble the vehicle again in the future at much greater cost.

See our Detailed Topic article All About Timing Belts for far more details.
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What are the symptoms of a bad fuel injector?

Symptoms could range from almost none, to a rough idle, to a misfire while driving, depending on the severity of the problem. On most post 1996 model vehicles, a check engine light will pick up moderate to severe failures. Diagnostic trouble codes (DTC) could range from a misfire, excessively rich or lean condition and even as an oxygen sensor out of range.

Professional technicians often use a combination of fuel trim readings, lab scope patterns, fuel pressure drop test and cylinder balance test to check for bad injectors.

Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information..
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What are the symptoms of a bad gas cap?

On vehicles built after 1996 one of the first symptoms would be a check engine light. Additional symptoms might include an odor of gasoline and a loss of fuel mileage, due to evaporation.

Please see our Detailed Topic Evaporative Emissions Systems and Fuel Caps for more information.
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What are the symptoms of a bad serpentine belt tensioner?
A typical serpentine belt tensioner has two major components.
1. A bearing mounted pulley
2. A spring mounted arm
Symptoms will depend on the part that fails. For instance, if the spring breaks, the belt will not be held tight. In this case symptoms will range from a squealing noise to the belt coming off.

When the pulley or bearing goes bad, there will normally be a squeak, roar or rumbling noise. When the pulley bearing fails, it may seize. This will cause severe squealing and even smoke. When the pulley or arm breaks, the belt will be thrown off, causing the accessories being driven to stop operating.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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What are the symptoms of a bad universal joint (U-joint) in a rear-wheel drive vehicle?
Universal joints, like many parts, fail in a number of ways. The symptoms generally depend on the nature of the failure. For instance, a joint with excessive slack will often give a clunk when shifting from reverse to drive. While this is common, lack of this symptom does not mean the joint(s) are okay.

Other possible symptoms of a bad universal joint include:
- A rotational squeak-noise when rolling slowly
- A vibration, especially at higher speed and felt in the seat
- A vibration on acceleration
- Leaking seals at the transmission tail housing
- Leaking pinion seals and differential pinion damage
- Broken transmission mounts
A bent or damage driveshaft can cause many of the same issues. Driveshafts are often damaged by improper U-joint replacement. Replacement of U-joints may appear straight forward but is best left to personnel with proper training and tooling.
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What are the symptoms of a cracked cylinder head?

Symptoms will vary based on the location and severity of the crack. A crack in the combustion chamber often results in an overheating issue and sometimes a misfire. If a misfire is present it may be more pronounced on startup and after sitting for a while. If the crack is in the head bolt or valve cover area, a slow loss of engine coolant is a common symptom.

See our Detailed Topic GM V8 Losing Coolant With No Apparent Leak for more information.
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What are the symptoms of a worn timing belt?

Most of the time there will be no symptoms. A timing belt ages and the adhesives and cords that hold it intact break down. Often, the first symptom is when it breaks and the vehicle quits running. This is particularly devastating on interference motors, as the engine may be damaged beyond repair.

Because there are usually no symptoms, the manufacturers recommendation for replacement should be strictly followed. It is also important to realize that time is as important as mileage. Most manufacturers state seven years as the interval to not be exceeded.

See our Detailed Topic article All About Timing Belts for far more details.
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What are the symptoms of broken motor mounts?

Depending on the vehicle symptoms might vary. Common is a clunk or knock noise on acceleration. Also fairly common is a vibration in the vehicle, particularly at idle. On rear-wheel drive vehicles, with a engine driven fan, often a noise will be heard because the fan contacts the fan shroud on acceleration.
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What are the symptoms of leaking valve cover gaskets?

With the vast number of engine designs in common use, symptoms vary greatly, depending on the specific engine. Very common is an oil burning smell. This is because many valve covers are above the exhaust. When they leak they allow oil to reach the hot manifold, where it burns. Another common symptom is oil dripping and saturating the suspension under the vehicle. This can create several additional problems as oil tends to destroy the rubber components.
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What are the symptoms of needing an injector flush?

Injectors are self cleaning and the need for additional cleaning is rare. The most common symptom is a rough idle. When an injector tip gets dirty, the spray pattern becomes more of a dribble than a spray. At very low speed, like idle, this may disturb air/fuel mixture. At higher speeds the affect will be less noticeable. A dirty injector will rarely cause a misfire at speed.

A failed injector is another matter. When injectors fail, they may stay closed, open or partially open. This can cause a misfire, check engine light and other problems. Failed injectors require replacement, flushing will not help.

Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.
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What are the symptoms of needing spark plugs?

For the most part there will be no symptoms. Modern vehicles are able to worn ignition parts. When spark plugs wear the gap is increased. This makes the ignition coil(s) work much harder. Eventually the coil(s) burn up, sometimes they also damage the engine computer. The first symptom is normally a breakdown and a very large repair bill. To prevent this, spark plugs and wires if present are replaced based on mileage. Waiting for a symptom can be very expensive.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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What causes a fuel pump to fail?

The two most common causes are running the pump low on fuel and contaminated fuel. The fuel in the tank cools the pump and adds head pressure to lessen the load. Since fuel in the tank flows through the pump assembly, contaminated fuel will quickly damage the pump motor.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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What could cause intake manifold on my 3.8L GM engine to have a small hole melted in it?

The most common causes are a plugged catalytic converter or restricted exhaust. Exhaust back-pressure flowing through the exhaust gas recycle (EGR) system can quickly burn through the plastic intake manifold.
For more information on please see our Detailed Topic, Catalytic Converters Problems.

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What could cause no fuel pressure, when I can hear the fuel pump running?

Assuming there is fuel in the tank there might be a number of causes. The motor on a pump, that you hear, is the electrical part, while the actual pump is mechanical. Fuel pumps can mechanically fail as well as electrically. It is also possible to loose suction, due to a plugged or bent pump intake. A crimped or kinked fuel line might block pressure and a failed regulator could let pressure drain back to the fuel tank.
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What could make my front wheel overheat and smoke?

Two common causes would include brakes that are dragging and a bad wheel bearing. Dragging brakes can result from bad brake hoses, sticking brake calipers or even a bad master cylinder. Friction can quickly generate a great deal of heat.

Wheel bearings that are too tight or mechanically failing will also generate a large amount of heat. In either case, severe damage is the normal result. The vehicle should be checked before any farther driving.

See our Detailed Topic article Adjusting Wheel Bearings for far more details on wheel bearings and Brake Hoses Can Bury You for far more details on brake hoses.
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What do the letters after a vehicle model name mean?

There is no standard meaning as each manufacturer assigns their own meaning. Generally speaking they indicate the level of options or special options on the vehicle. For example LE might mean limited edition on one vehicle and luxury edition on another. Such a vehicle would be equipped slightly different from an SE (special edition) of the same make and year.
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What does the term maintenance item mean?

A maintenance item is normally used to describe an automotive part that is subject to wear in normal use. For instance, spark plugs are considered maintenance items, because they wear out by doing their job. The term is often used by insurance companies, when deciding claims payments. For instance the fender of the vehicle does not wear out, so replacement cost might be paid in full. If a serpentine belt was damaged in an accident a depreciated amount might be paid, based on the wear present on the old belt. If it were half worn, only half the replacement cost might be paid.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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What does “full coverage” automobile insurance mean?

Full coverage generally means that both liability insurance and coverage for your vehicle are included. Liability will pay for damage and injury to people other than the policy owner and when the driver is at fault. Other coverage, such as collision, may cover the policy owner’s property. It does not mean that everything that happens to the vehicle is covered, except as listed in the terms of the policy. For instance, an expensive aftermarket stereo may not be covered if stolen, unless it is declared.
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What is a fuel injector?

A fuel injector is a valve that controls the amount of fuel the engine receives. With electronic injection, a spring holds the valve closed until the magnetic coil opens it. The injector is either open or closed and the amount of flow is controlled by the period of time the valve is held open. The time open is called the pulse-width and is measured in milliseconds. The longer the pulse-width the more fuel flows. The engine computer controls pulse-width based on several factors and helps keep the fuel-air mixture correct.

Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.
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What is a MAP sensor?

The MAP or manifold absolute pressure sensor detects the amount of vacuum or pressure in the intake manifold. The power control module uses this and other information to determine the load on the engine and sometimes exhaust gas recycle (EGR) flow, among other things. As the throttle opens at lower engine speeds, intake vacuum decreases. This decrease in vacuum is measured by the MAP sensor and relates to engine load.
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What is a mass air flow sensor?

The mass air flow or MAF sensor detects the amount of air in grams per second that enters the engine through the air box. The power control module uses this and other information to determine the amount of fuel that should be needed to furnish the cylinders with the proper fuel/air mixture or 14.7 to one.
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What is a timing belt?

The timing belt is a toothed belt, normally internal to the engine, that connects the crankshaft to the camshaft(s). By design, it does not slip as the teeth of the belt, fit over matching cogs on the sprockets. This allows the camshafts to stay in time with the crankshaft, and keeps the pistons from striking the open valves. Over time, the belt deteriorates and has to be replaced. Most manufacturers state seven years as the outside limit of timing belt life.
Please see our Detailed Topic article All About Timing Belts for far more details.

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What is an interference engine?

An engine design where the valves and pistons occupy the same area, at different times. This improves performance, but has the risk of engine damage when the timing device, such as the chain or belt fails. Please see our List of popular Asian and Domestic interference engines for more details.
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What is meant by the term bleed, in regard to automotive systems?

To bleed usually refers to the process of removing air from a fluid driven system. Typical examples of things that are bled include, brake, clutch, cooling and power steering systems. Since air can be compressed it is detrimental to a system that depends on fluid pressure. Air in the brakes or clutch will compress and make the pedal spongy. Air in the power steering will cause noise and erratic operation. Air in a cooling system can cause hot spots with no cooling, poor circulation and will greatly increase corrosion.
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What is the affect of driving a vehicle without the EGR system working?

The exhaust gas recycle or EGR system is designed to help prevent detonation or spark knock. When these conditions are allowed to continue, they can drastically raise the temperature and pressure in the combustion chamber. This may have the affect of blowing head gaskets and damaging internal engine components.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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What is the best spark plug for my vehicle?

Most engines will perform best with the original equipment spark plug. For instance, Delco in GM, Motorcraft in Ford, Toyota brand in Toyota, etc.
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What is the difference in an interference and non-interference engine?

In order to gain performance, some engine hold the valves open longer and further on the exhaust and compression strokes than others. In each case, the piston is rising as the valve is closing. The engine timing prevents them from hitting, even though they occupy the same place, at slightly different times. If the engine loses camshaft timing, due to a timing belt or chain fault, the valves can hit the pistons causing great damage. In a non-interference engine, there is adequate clearance to prevent this, though such an engine will normally have less performance.

See our Detailed Topic article All About Timing Belts for far more details.
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What is the freeze point of windshield washer fluid?

There is no standard freeze point for windshield washer fluid. Instead, the freeze point is determined by the concentration of methanol. This varies by manufacturer and is often listed on the label. Concentrated windshield washer fluid can be mixed in the dilution desired to achieve a given freeze point. For instance, one manufacturer list:
ratio of
concentrate
to water
Freeze point
(Fahrenheit)
1 to 1 -49 degrees
1 to 2 -13 degrees
1 to 3 zero degrees
1 to 4 10 degrees
1 to 5 14 degrees
1 to 10 26 degrees
Methanol is toxic and can be flammable. Concentrate should never be mixed in excess of the protection required.

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What is the purpose of an EGR valve?

EGR or exhaust gas recycle, adds exhaust gas to the combustion chamber under certain circumstances. This reduces the temperature and helps lower oxides of nitrogen emissions and aids in preventing spark knock and detonation.
For more information on exhaust gas recycle or EGR valves, please see our Detailed Topic How does and EGR valve work.

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What makes a catalytic converter fail?
Catalytic converters, might fail for a number of reasons. Age is one issue, but failure before 200,000 miles often has other factors:
- An impact to the converter may cause internal damage
- A leaking intake manifold may allow coolant to enter the intake and the converter
- An engine misfire, allows excessive fuel to enter the converter
- A malfunctioning oxygen sensor can cause excessive fuel in the converter
- Oil entering the intake stream from a failed gasket
- Excessive use of some fuel additives could damage the converter
Of course this list is not all inclusive, but these are all relatively common factors. For more information on catalytic converters please see our Detailed Topic, Catalytic Converters Problems.
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What percentage of antifreeze to water is necessary to maintain a -34 degrees Fahrenheit freeze point?

Most experts agree, a concentration of 50 percent distilled water and 50 percent antifreeze will offer freeze protection to -34 degrees Fahrenheit. A 50/50 concentration also offers good corrosion protection and adequate cooling.

% Antifreeze Freeze Point Fahrenheit

10%
25 degrees F

20%
16 degrees F

25%
10degrees F

30%
4 degrees F

35%
-3 degrees F

40%
-12 degrees F

45%
-22 degrees F

50%
-34 degrees F

60%
-48 degrees F

65%
-62 degrees F

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What would cause a head gasket to start leaking again, shortly after replacement?

Several things could cause such a problem. For instance if the head were warped, it will not provide an adequate sealing surface. Another cause is low spots in the cylinder head or engine block. This is particularly common when the leaking head gasket was not repaired in a timely manner. Other causes could be that the root cause of the failure, spark knock, detonation, overheating, etc. was not corrected. Head gasket failure is almost always a symptom of another problem.
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What would cause a loud popping noise, coming from between my engine and transmission?

Engine damage, such as a bad rod or main bearing will cause such a noise. Another issue that is often mis-diagnosed as an engine problem is a cracked transmission flexplate. The cracked flexplate pops as it rotates and sounds very much like an engine problem.
For a detailed explanation of the problem, please see What Causes a Flexplate to Crack.

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What would cause a serpentine belt to smoke?

Smoke is the normal symptom of heat and heat on a belt indicates friction. The most likely causes would be a binding or misaligned belt-driven accessory or idler pulley.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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When does a serpentine belt need to be replaced?

When there is fraying, deep cracking or pieces missing, a belt must be replaced. Fraying is when cords are separating from the sides or back of the belt. Cracks in the back side of the belt also signal a need for replacement. The back is the side without ribs. I also recommend replacement at seven years of age, regardless of condition.

Small cracks in the ribs of the belt do NOT indicate a need for replacement, unless other conditions dictate. Also, belts do wear out. The grooves wear and no longer fit the pulley, which can result in slip. Gauges are available to check belts for wear and any belt revealed to be worn should be replaced.

For more information on belts, see our Detailed Topics article, About Serpentine Belts.
For more information on belt inspection and EPDM belts, please see our Detailed Topic, Symptoms of A Bad Serpentine Belt and EPDM Belts.

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When I accelerate my engine loses power and the check engine light comes on.

Many things can cause a miss under acceleration. Bad ignition spark plugs, wires or coils will generally miss under load. This will normally set a P0300 code and the fuel mixture may indicate rich.

A clogged fuel filter, weak fuel pump or bad fuel pressure regulator will also cause the same type symptoms. In this case, if there is fuel trim data, the fuel mixture may indicate too lean. Test driving with a fuel pressure gauge attached will indicate if this is the problem.

Restricted exhaust, from a plugged catalytic converter or muffler can also cause a similar symptom. Testing the exhaust back pressure is the best way to determine if a restriction exist.
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When I press the down button on my driver’s power window, I can hear a motor run, but the window does not go down. Any ideas?

If you can hear the motor run the motor and switch are likely okay. Two other possibilities, would be the window regulator and the window motor clutch.

The regulator is an assembly of metal, plastic and cable that converts the rotary motion of the motor into the up and down lift of the glass. Often the guides wear out or break and the cable comes off the track. In this case replacement of the regulator is needed.

The window motor clutch can often be serviced separately from the window motor. This saves the cost of a replacement window motor, and gives good service, if done properly. Either job requires a very large rivet tool to replace the rivets that hold the motor and regulator to the door frame.

For more information on preventing power window problems, see our Detailed Topics article, Preventing Power Window Problems.
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When I start driving my vehicle is quite but after a while, there is a whining noise that increases with vehicle speed. The noise is worse if I turn hard to the right or left?

Whining noises that increase with vehicle speed are very often caused by wheel bearings. Turning hard right or left loads the front bearings and will cause the noise to increase. Wheel bearings also tend to get louder after driving a distance. I would suspect one of the front wheel bearings.
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When I turn on my air conditioner or defrost, my engine bogs down, like it is about to stall. What would cause this?

Engine speed is controlled by a component called an idle air control or IAC servo. When the air conditioner is turned on, the compressor loads the engine. The load change causes the engine to slow down. When operating properly, the IAC will correct the idle speed, almost immediately. When the IAC sticks or works slowly, there may be a noticeable change in speed when engine load changes.
For more information, please see our Detailed Topic Idle control and electronic throttle control.

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When my battery was replaced the hold down broke. The shop said it was not important, what do you think?

I would disagree for several reasons. First, an improperly mounted battery can bounce around and vibrate. This can drastically shorten the life of the battery. It can also cause the battery to leak and the acid can damage expensive components. If not properly secured, the battery can fall out of place and cause considerable damage. The mounting should be properly repaired and the battery properly secured in the vehicle.
For more information, please see our Detailed Topic The Cost of Battery Corrosion.

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When my fuel tank is low there is a whining noise in the rear of my car?

Low fuel is a leading cause of fuel pump failure. On newer vehicles, running out of fuel one time can damage the fuel pump. Fuel in tank cools and lessens the load on the fuel pump. When low on fuel the pump heats up and works much harder which can cause a whining noise.
For more information, please see our Detailed Topic, What Causes Fuel Pumps To Fail.

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When replacing a timing belt, should I also replace the idler pulleys?

The idler pulleys can be replaced for no additional service charge at the time of timing belt replacement. The charge to replace them later is almost equivalent to replacing the timing belt again. If they seize, they can also destroy the timing belt. Since they generally have the same mileage as the timing belt, I find it most economical to replace them at the same time the timing belt is replaced.

For more details on timing belts, check the AGCO Automotive article All About Timing Belts.
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Where can I find a list of interference and non-interference engines?

You can find a list of common Domestic and Asian interference engines on agcoauto.com, by clicking here.
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Where is the idle control valve on my Chevy Silverado?

Many modern vehicles, like the Silverado, use an electronic throttle body. These vehicles no longer require an idle control valve as the PCM now directly controls the throttle and idle is obtained by metered throttle opening.

For more information, please see our Detailed Topic idle control and throttle bodies.

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Where is the rear main seal of an engine located?

The rear main seal is located around the back of the crankshaft, where it exits the engine block. The transmission bolts to the rear of the engine and the crankshaft as well. This is why it must almost always be removed to replace the rear main seal.

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Which Ford engines use the two-piece spark plug that is prone to breakage?

The two piece plugs were used in the 4.6L, 5.4L and 6.8L 3-Valve engines; The two Valve engine does not use this plug.
FORD:

2005-2008 Mustang
2004-2008 F-150
2005-2008 Expedition, F-Super Duty
2006-2008 Explorer,
F-53 Motor home Chassis
2007-2008 Explorer Sport Trac

LINCOLN:

2005-2008 Navigator
2006-2008 Mark LT
MERCURY:
2006-2008 Mountaineer
For more information, please see our Detailed Topic, Ford Spark Plug Breakage.

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Why do catalytic converters get so hot?

Exhaust gas flowing through the converter is hot and the chemical reactions within the converter adds additional heat. Most converters operate in the 600 to 900 degree Fahrenheit range. When raw fuel enters a converter such as with an engine misfire the temperature can get significantly higher and quickly damage the converter.
For more information on please see our Detailed Topic, Catalytic Converters Problems.

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Why do diesel engines not need spark plugs?

Spark plugs are used to ignite the fuel/air mixture in gasoline engines. With the diesel engine, the fuel/air mixture is compressed until it spontaneously combust, not requiring a spark.
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Why do estimates to replace my timing belt vary so greatly?

Many shops quote only the price of the belt with installation. They may do this to make their prices seem more competitive, when many times they are merely excluding things included in other estimates. The largest part of the job is the charge for disassembling the engine. While the engine is disassembled access to several other parts are greatly eased. For instance the water pump is normally easily accessible. Since these parts often fail around 100,000 miles, it is prudent to replace them while the engine is apart. The same with the front crankshaft seal, camshaft seals, tension devices and outside belts.

Many times we receive vehicles for repair that have recently had a timing belt replaced and now have a camshaft seal leaking. The oil has leaked on the new belt, ruining it and requiring replacement. The entire job must be re-done because of something that could have been addressed during belt replacement for minimal cost. Such practices are risky and not at all cost effective. For far more detail, check the AGCO Automotive article All About Timing Belts.
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Why do gaskets fail?

The reasons tend to depend on the type of gasket. Gaskets fail from too much heat, too much pressure, corrosion on the sealing surfaces or an inferior sealing surface produced in manufacturing. We tend to see far more gasket failure in engines that have had infrequent oil changes. Extended oil change intervals tend to allow gaskets and seals to harden. When this occurs the gaskets may no longer tolerate the pressure and start to leak. Leaking intake and oil pan gaskets on GM vehicles, the problem appears to me to be inferior machine work. The sealing surface is too rough and in short order the gasket fails.

For much more information on leaking intake gaskets see our Detailed Topic section.
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Why does the speedometer go out on so many Chevy Silverado trucks?

The 2003 through 2006 GM truck instrument panel cluster (IPC) used defective stepper motors. These vehicles are normally under recall for up to 70,000 miles. To have the problem repaired under the recall, the vehicle has to return to a GM dealership. If the vehicle is out of the recall mileage, any independent shop can make the repair for you, often at a lower cost.

See our Detailed Topic article GM Dash Gauge Failure for far more details.
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Why was I not notified there was a recall on my vehicle?

The National Highway Traffic Safety Administration or NHTSA handles vehicle safety recalls. The manufacturer will normally attempt to notify the original purchaser of the vehicle, by mail. This involves a post card to the address on file from the time of sale. This may not reach the current owner of the vehicle or an owner who has moved. The NHTSA also maintains a website where recalls can be found.

Please check the agcoauto Links category, for a link to NHTSA.
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Why would a dead battery cause my vehicle to fail State inspection?

In States with mandatory emissions testing, vehicles from 1996 and up have to pass the on board diagnostics or OBD test. Failures and pass/fail test results are stored in the vehicle computer. When the battery is disconnected or dies these results are lost, causing an inspection failure. When the battery is replaced, the tests will begin to run. Running readiness-tests can take up to several days driving. The vehicle will fail inspection until the tests are successfully completed.
For even more information on check engine lights, see our Detailed Topics article, Failing State Inspection.

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Why would my engine start leaking oil at several places, all at once?

One common cause of multiple oil leaks is a bad PCV valve. When the PCV valve fails to remove crankcase vapors, pressure can build and blow out gaskets and seals. Other causes include infrequent oil changes, which can allow gaskets and seals to harden and engine over-heating.
For far more information on PCV valves please see our Detailed Topic, Symptoms of a Bad PCV valve.

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Why would my vehicle crank over but not start?
Four things are needed for a vehicle to start.
1. Correct fuel pressure.
2. Adequate ignition spark.
3. Adequate engine compression.
4. Correct engine timing.
A few things that result in low or no fuel pressure or a bad fuel pump, lack of power, ground or signal to the fuel pump or of course, being out of fuel. Lack of ignition spark can be a failed power control module, input sensor, ignition coil, distributor among other things. Suddenly losing engine compression is normally a result of a broken timing belt/chain or valves stuck in the open position. Incorrect timing can result from a slipped timing belt/chain or any of a few sensors that help control timing.

Diagnosis would begin with a fuel pressure test. From there, it depends on the findings as to what would be the next step.
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Why would the serpentine belt on my car come off?

If the belt did not break, the cause will almost always be a belt alignment issue. Many times one idler pulley that guides the belt will wear out. Another cause might be failure of the belt tensioner. The tensioner is a spring loaded device that keeps the belt tight. The tensioner can seize or the spring can fail. On models that do not use tensioners, the belt can come loose due to slippage of the adjusting mechanism. A failed belt-driven accessory, such as an alternator of air conditioner clutch/compressor can cause the belt to come off. Also check the crankshaft pulley. The rubber harmonic balancer mounting often breaks, causing the pulley to run out of alignment.
For more information, please see our Detailed Topic, About Serpentine Belts.

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Will a bad PCV valve cause my engine to develop sludge?

Crankcase ventilation is very important in removing moisture, which is a leading contributor to sludge buildup. Driving short (less than five miles) trips and infrequent oil changes will make the problem vastly worse.
For far more information on PCV valves please see our Detailed Topic, Symptoms of a Bad PCV valve.

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Will changing to iridium spark plugs increase my fuel mileage?

Iridium is a very durable material and helps spark plugs last longer, in engines that are designed to use them. Installing iridium plugs in an engine not designed for them will have no affect on fuel mileage over replacing with the specified plug.
For more information on spark plug problems, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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Will spark plugs with multiple electrodes increase fuel mileage and performance?

The spark plug simply provides a gap for the electricity produced in the coil(s) to jump and fire the air fuel mixture. The number of electrodes will have no affect and will not increase mileage or performance.

See our Detailed Topic article Wasting Money and Not Saving Fuel for more details.
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With my engine off and the oil filler on my engine open, a lot of smoke comes out. What could be the problem?

Excess smoke coming from a non-running engine crankcase is often a result of condensation. Short trips with a vehicle tends to allow moisture to collect, due to condensation in the crankcase. Driving the vehicle for longer distances may help as will changing the oil more frequently. In more severe cases, moisture may also come from leaking engine gaskets, particularly leaking head gaskets and intake gaskets.

For much more information on leaking intake gaskets see our Detailed Topic section.
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Maintenance Definitions

Accessory Belts

Belts are used to drive the accessories on an engine (e.g., the alternator, air conditioning, power steering, etc.) Most engines now use serpentine belts rather than V-belts, that were used years ago. Serpentine belts give much less problems, but do still need to be replaced.

Accessory belts are on the outside the engine and are easily inspected. Belts that are frayed, cracked or glazed need replacement, as they can break and cause engine damage. Also belts that squeal may be candidates for replacement.

Most newer vehicles use belts made of EPDM, a very tough material that does not crack. These belts must be checked for wear, with a gauge, made for the purpose. When these belts wear, they may slip and create a great deal of heat and damage driven components.

Under normal conditions, accessory belts last between 50,000 and 65,000 miles. EPDM belts may last even longer, but should be replace after seven years are when indicated by a wear gauge.

Accessory belts should not be confused with the timing belt, which is internal to the engine. Timing belts are covered in their own section.
For more information on belt inspection, please see our Detailed Topic, Symptoms of A Bad Serpentine Belt and EPDM Belts.

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Air conditioner condenser

Not often considered as a maintenance item, cleaning the air conditioner condenser can greatly extend the life of the system. Condensers are exposed to air flow and tend to collect bugs and dust. Gently hosing the debris from the condenser with a hose may help lower compressor head pressure and increase efficiency. Air conditioner condensers should be cleaned annually, best before the start of summer.
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Air Filter

Engines run on fuel, but they also use air. In fact they use 14.7 times more air than fuel. Unfortunately even clean air still contains a lot of minute dust particles. The air filter attempts to remove these particles before they enter the engine. In time the filter becomes clogged and the air flow will become restricted. When this happens the engine loses power. Contrary to common belief and advertising, even a badly restricted air filter will not reduce fuel mileage.

The best air filter to use is the one supplied by your vehicle manufacturer. Substandard air filters can have poor seals and filter media. These faults can drastically increase wear to the cylinders and also damage air flow meters. The life of the air filter depends on the amount of dust in the air that passes through it. In very dusty areas they can become clogged in as little as 5,000 miles. Under normal conditions they should last 30,000 to 50,000 miles or more. Vehicles that have indicators on the filter housing can also use that as a guide. Care must be taken when replacing the filter. Debris that can fall from the filter can easily be drawn into the engine. Carelessly replacing the air filter can actually cause far more problems than the old air filter.
For more information, please see our Detailed Topic When Should Air Filters Be Replaced.

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Automatic transmission service

Automatic transmissions produce debris as part of their normal operation. Metal particles and clutch material are worn from their original parts and circulate with the fluid until removed by the filter. The fluid also loses some of its properties over time, from continual exposure to heat and use.

Most automatic transmissions have a removable filter. With proper service on these units, the pan is removed, the old fluid drained and the filter is replaced. In many instances the valve body bolts may be tightened to specifications and the bands adjusted if so equipped.

We recommend this service at three years or 50,000 miles, whichever occurs first. On other units [Honda, some Mazda, some Ford, etc.] replacement of the internal filter may require disassembly of the transmission. On these models service is performed by draining and filling the unit, twice in succession if needed.
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Batteries

Batteries are not often thought of as maintenance items. Instead many folks wait until they fail before replacing them. This can lead to a very inconvenient situation and over work the charging system as well. Batteries suffer 100% mortality and most die between three and four years. Some die suddenly and can leave the vehicle stranded. Others die slowly and cause the alternator and starter to work much harder

Since all batteries die, many folks find it more convenient to replace them before this occurs. Three-years is a pretty safe guideline in South Louisiana. Some last longer, but their low cost and unpredictable nature makes trusting them considerably longer pretty cost ineffective.
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Brake fluid

Most brake fluid is made of alcohol and absorbs moisture from the atmosphere. Moisture content will lower the boiling point of the fluid and increase corrosion to the system. This occurs 24 hours a day and whether the vehicle is driven or not. For this reason, time is a better indicator of when to change rather than miles.

Color is not a reliable indicator of moisture content. Some fluids that are clear may be contaminated and others that are dark may be okay. Brake fluid can be tested with a refractometer, to reveal it’s moisture content. Without such an instrument a good rule of thumb would be every two to three years and before any brake service.
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Cabin filter

The cabin filter or heating, ventilation and air conditioning (HVAC) filter is an often overlooked maintenance item. Though some vehicles have had these since the early nineties, many vehicle owners are not familiar with them.

The cabin filter is much like the air conditioner inlet filter in your home. It removes dust and debris from the air before it is circulated through the evaporator and heater cores. When they become restricted, the fan may draw too much amperage and damage the circuitry or even the automatic temperature control assemblies if so equipped.

Not all vehicles are equipped with cabin filters but many are. They are normally replaced every 15,000 miles. If you are not certain check your vehicle owner's manual.
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Coolant/Antifreeze

Coolant, also called antifreeze performs several functions. To perform these functions it is mixed with water. In South Louisiana the proper mixture is 50/50 or half coolant and half water. The water performs the engine cooling function. Since water freezes at 32 degrees Fahrenheit, the addition of antifreeze is necessary to lower the freeze point. When water freezes it expands and this expansion can crack an engine block and cause severe damage. Antifreeze lowers the freeze point below that which is likely to occur.

An even more important function is corrosion protection. Coolant works in several ways, depending on its makeup to prevent corrosion. There are several types of coolant each using a different methods of protection. Many are not compatible with one another and it is always advisable to stay with the type of coolant specified by the vehicle manufacturer.

Over time the corrosion inhibitors are depleted leaving the cooling system unprotected. New coolant has reserve alkalinity and a pH of 8.0 or higher. As coolant ages, pH tends to fall and the coolant becomes acidic, causing severe damage. The protection against freezing is also lost over time.

The change interval for coolant is more dependent on time than miles. Because it is a chemical reaction, it occurs 24/7, whether the vehicle is driven are not. To be safe it is normally replaced every two to three years, when the pH approaches 7.0 or when the specific gravity indicates an insufficient freeze point.
Please see our Detailed Topic Symptoms and Causes of Cooling System Problems for a lot more information on coolants and corrosion.

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Differential fluid

Differential fluid lubricates the gears, bearings and if present clutches of the differential. A differential is necessary to transmit power to the drive wheels of the vehicle. The input from the transmission passes through the gears of the differential. Here the direction of force is changed and applied to the drive wheels. The churning of these gears through the lubricant produces pressure. This pressure is vented to the atmosphere. The same vent allows moisture to enter the system. The fluid, not only lubricates, cools and cleans the gears, it also suspends any moisture that enters the system.

In time the lubricant breaks down and becomes dirty. On many front wheel drive vehicles the differential is part of the transmission. It is serviced when the transmission is serviced. On rear wheel drive and all vehicles with a separate differential, it needs to be serviced separately. This is often recommended around 50,000 miles, but may be as low as 15,000 when towing or as high as 100,000 in some cases.
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Fuel filter

The fuel filter removes impurities that are in the fuel. Impurities enter fuel in transport and shipping and in the storage tanks at fuel stations. They can also come from rusted or deteriorated fuel tank linings in vehicles.

A small amount of trash can ruin fuel injectors, fuel pressure regulators and even damage an engine. Fuel filters should be replace about every 45,000 to 60,000 miles, unless they are mounted in the fuel tank. Fuel filters, that are located in the tank, are normally good for about 100,000 miles

Fuel filters should also be replaced whenever there is a fuel system problem, like fuel pump failure or contaminated fuel enters the system.
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Hoses

Coolant hoses are much better today than they were a few years ago. Many last ten years are more. The hoses that come on a new vehicle may also be better than the replacements that are available.

Because of the high quality of the original hoses, it is often best to have them inspected, and replace only when needed. Inspection should be at three years and every year there after. Replace hoses when they are found to be swollen, soft, hardened, cut, frayed or when inspection shows need for replacement.

There are also power steering hoses and air conditioner hoses. With these too, inspection is the better policy and replace as needed, rather than at specific time intervals.
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Maintenance Defined

Maintenance is service performed and parts replaced to reduce greatly the odds of more expensive components failing. For instance coolant is replaced in the hope of preventing corrosion damage to radiators, heater cores and engines. The cost of the coolant replacement is a fraction of the cost of the repairs it can prevent.
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Manual transmission fluid

The lubricant used in a manual transmission gets dirty, can absorb moisture and suffer diminished properties over time. Debris is produced by the gears, bushings and moving components. Almost no manual transmissions contain filters and replacing the fluid is the only way to remove debris that accumulates.

As a general rule we recommend manual transmission fluid replacement between 50,000 and 100,000 miles, more often when towing. It is important to remember transmissions use many different types of lubricants today. Always check with service for the proper type before replacing transmission fluid.
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Pack wheel bearings
Many new vehicles use sealed wheel bearings that cannot be serviced. On others, bearings need to be removed, cleaned, packed with fresh grease and the seals need to be replaced. On some vehicles the front bearings are able to be packed and on others vehicles the rear may be serviceable as well.

On vehicles with bearings that can be packed, the service is normally performed at each brake service or around 50,000 miles.

See our Detailed Topic article Adjusting Wheel Bearings for far more details.
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PCV Valve

The positive crankcase ventilation or PCV valve, removes fumes and pressure that is generated in the engine. In time the PCV valve may plug up. When this occurs pressure may start to build. Pressure buildup can damage oil seals and gaskets and they often blow out, resulting in oil leaks.

Under normal use the PCV valve should be replaced about every 80,000 to 100,000 miles but can fail as often as 50,000 miles. They should also be tested whenever engine service is performed and replaced sooner if needed.
For more information, please see out Detailed Topic What are the symptoms of a bad PCV valve.

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Power steering fluid

Power steering fluid comes in several different types. Most vehicles use a hydraulic oil, but some vehicles use automatic transmission fluid and still others a vehicle-specific fluid. Power steering fluid acts as a lubricant, cleaner, seal conditioner, coolant and hydraulic fluid for the system.

Like most fluids, in time, power steering fluid loses the properties that help it to work. It also becomes laden with debris and since most systems do not have a filter, it must be replaced. Replacing power steering fluid between 50,000 and 100,000 miles is normally adequate, unless recommended sooner by the manufacturer. Though not the main intent, properly replacing power steering fluid may also help with power steering noise as well.
For more information, please see our Detailed Topic How To Replace Power Steering Fluid.

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Spark plugs

Spark plugs provide a small (0.03" - 0.90") gap that generates a spark, when electrical current jumps across it. This spark in turn ignites the compressed fuel-air mixture. The combination of extreme heat and high voltage cause the electrodes, that form the gap to wear. As they wear the gap gets wider and the plugs no longer fire as efficiently as before.

Depending on the construction of the spark plug, they normally wear out between 30,000 and 100,000 miles. Standard spark plugs wear out closer to the minimum and platinum and iridium plugs closer to the maximum listed.

It is also important to consider that spark plugs are made unusable in other ways than just the gap. They can become fouled, or the electrodes covered with foreign matter. They can also leak between the ceramic and the base.
For more information, please see our Detailed Topic When Do Spark Plugs Need To Be Replaced.

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Timing belts

Many engines have an internal timing belt. This is different from the external accessory or serpentine belts. The timing belt drives the camshaft(s) and cannot be readily inspected. There are specific recommendations for timing belt replacement, given by manufacturers. Timing belt replacement is normally recommended between 60,000 and 105,000 miles, depending on design.

Because access is difficult, other wear items, in the area of the timing belt, are often replaced with the timing belt. The belt idler pulley(s), front crankshaft and camshaft seal(s), water pump, etc. may be suggested. The reason for this suggestion is these other parts do fail, and the cost of replacement is much less, while the timing belt is off.

There is a great deal of price difference, between a complete job and merely replacing the belt. Iit is wise to know exactly what is being charged for when replacing a timing belt.

For more information on timing belts see our article All About Timing Belts.
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Tires

Tires wear out in time and the tread becomes thin. This is not the only way that tires fail. Tires also have a life expectancy of six-years. As tires age, the adhesives that hold them together as well as the rubber they are constructed of, deteriorates. When this happens, they can separate and blow out.

Tires must be inspected for age, as well as cuts, bulges and wear to the tread. Tires should be replaced when tread depth reaches 2/32 inch or when the age reaches six-years. Age can be determined by the DOT number that will be imprinted on the sidewall. The last four digits show the week and year of manufacture.
To learn how to read a tire date code, please see How to read a DOT number.

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Transfer case fluid (4WD only)

The lubricant in a transfer case gets dirty, can absorb moisture and suffer diminished properties over time. Debris is produced by the gears, bushings, chain and moving components. As a general rule we recommend transfer case fluid replacement between 50,000 and 100,000 miles, more often when towing. Transfer cases, like transmissions often use a specialized lubricant. Service data should always be consulted before replacing transfer case fluid on any four-wheel drive vehicle.
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New and Used Vehicles, Buying and Selling

AGCO Auto Used Vehicle Check List

Download and print this handy form to help you evaluate used vehicles.
AGCO Auto Used Vehicle Check List

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Am I under any obligation to divulge any problems I am having with my car to a dealer if I am trading it in?

Laws may vary from State to State, but generally a dealership is considered a professional. A professional is held to a higher standard and expected to know what they are buying. This may also be one reason most dealers offer lower prices when buying used vehicles? If you are not asked and do not offer any information, legally you should be okay. If asked, I would feel obligated to tell what I knew. It likely will not make that much difference in the trade-in price.
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Are there certain new vehicles that are better to buy?

Most new vehicles will give good service if properly maintained, and few vehicles will if not maintained. What is more important is to get a vehicle that meets your needs. For instance if fuel mileage is very important to you, then do not consider an SUV. By the same token, if you have a large family buying a compact vehicle will not normally be a good choice.

Other things to consider are the popularity of the vehicle and the number of dealers in your area. For example Chevrolet is very popular and there are many dealers to supply parts and warranty service. More obscure brands may have only one dealership, and if they go out of business, you may have difficulty obtaining warranty or parts. Also, brands that are new to the US market may be somewhat risky.
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Are there things I can check to see if a vehicle has been wrecked and repaired?

An expert may be required to spot a well repaired vehicle, but well repaired vehicles present few problem. With less well repaired vehicles there are several tell-tale signs, the average person can spot. Vehicles with such signs will generally be considered poorly repaired and should be avoided. See our Detailed Topic Spotting Wrecked Vehicles for several examples.
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At what age does a used vehicle represent the greatest value?

Maximum depreciation is often around three-years. That is, the vehicle has lost a higher percentage of its value than it will continue to lose. Some vehicles lose as much as 60 to 70% in three years. At only three years almost any quality built vehicle will still be in very good condition. Buying such a vehicle and following a rigid maintenance schedule, will provide a very low overall cost.

For much more information on calculating the true cost of a vehicle, see our Vehicle Cost Calculator in the Cost Saving Calculator Category.
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Beyond just the price, what things should I consider when buying a new car, from a cost standpoint?

Newer vehicles normally employ a lot of very expensive technology. When technology breaks there is a significant cost. For instance most drivers do not know they have an active suspension system or enjoy any benefit from it. When the system malfunctions and a light flashes on, there is a huge repair cost.
Aftermarket navigation systems cost a fraction as much as onboard systems and offer the same features. When the aftermarket system fails it may be inexpensively replaced. Factory systems are extremely expensive to repair. Sport packages with large diameter tires also add significant cost with no benefit, other than appearance. From a cost standpoint, the less gadgets the lower the overall cost to maintain.
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Buying a new vehicle, I have been told by the salesman, I really should buy a five-year 70,000 mile extended warranty.

I advise against the purchase of such warranties. Your vehicle manufacturer's warranty covers the vehicle for three years and 36,000 miles. You are being charged for five years and 70,000 miles but only getting two year and 34,000 miles of coverage.

Extended warranties are nothing more than a term insurance policy with limitations. Warranty companies make money simply because they charge a lot more than they spend. Even after administrative cost, promotion, commissions and claims there is a lot of money left over. This means most people buying an extended warranty will pay more for the policy than they would have paid for repairs.

Most salespeople and dealerships receive a commission payment for selling these policies. I feel this has a lot more to do with their zeal than concern for the client. Put the money into a CD, pay for your own repairs and at the end of the term, you will have money left.
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Buying a used car on a weekend, when I cannot have it checked, is there a way to protect myself?

I would never advise buying a vehicle without a thorough inspection by a trusted mechanic. The price difference between new and used is substantial. Someone is taking a loss to sell this vehicle. There can be many reasons for that and you need to be sure it is not because of a problem.

If you inform the seller you are truly interested and offer a deposit, most will hold the vehicle. On the deposit you should write, "Subject to inspection by my mechanic." This will normally protect you if a major problem is found. Remember though, a deposit is a commitment, and you are not allowed to just change your mind.
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Buying a used car, is there a check list of things to look and lookout for?

Read through the other questions in this section for additional input and then download the AGCO Auto check list and you should be all set.

AGCO Auto Used Vehicle Check List
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Can changing tire size void the warranty on my new car?

Terms vary among manufacturers but technically any modification to the vehicle could cause the warranty to be void. This is more likely if a problem develops related to the wheels or tires. I may also be subject to how drastically the size is changed from the stock recommendation. A warranty is a contract. If the terms, of the contract, are changed by either party, the agreement may no longer be valid.
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Can I donate my vehicle to charity if I have no title?

No, without a title you cannot establish that you own the vehicle. A title is needed to establish ownership and to protect any lien holder that may be listed. If the title is lost, a duplicate can usually be obtained. We should contact the Department of Motor Vehicles, in the State where the vehicle is registered.
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Can I save money by leasing a vehicle?

Leasing is very similar to renting, only with a contract that is binding. There are usually restrictions on miles you may drive, and should you decide the vehicle is not for you, there is normally no inexpensive way out. With leasing you gain no equity and simply make payments. The only advantage is a lower monthly payment, but considering you are buying nothing, that may be a small consolation.
For more information, please see our Detailed Topic, Problems With Automobile Leasing.

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Can I tell where a vehicle was built before I buy it?
The country in which a vehicle was assembled is part of the vehicle identification number or VIN. The first digit of the VIN is a code that reflects the country of assembly as follows:
- 1 = USA
- 2 = Canada
- 3 = Mexico
- J = Japan
- K = Korea
- E = England
- W = Germany
- Z = Italy
For much more information on US built and imported vehicles please see our Detailed Topic section.
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Can odometer rollback be traced?

With digital odometers and the right equipment, rollback can be almost un-traceable. This is another reason that service records are important. A thorough set of service records, showing mileage and date of service, substantiates the mileage on the vehicle. Many states, including Louisiana, record mileage during State inspections. This information, with a bit of math can narrow the possibility of rollback substantially.
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Do I need the title to my car to send it to a salvage yard?

Yes, salvage yards are required to have titles for the vehicles they process. This prevents stolen vehicles from simply being disposed of and keeps vehicles from being unlawfully confiscated. It also protects lien holders who have their name registered on the title.
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Does a manual shift transmission get better fuel mileage than an automatic transmission?

I think it is possible that a professional driver could get very slightly better mileage with a manual shift. For the vast majority of drivers the performance of a modern automatic transmission would be almost impossible to beat.
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How can an abandoned vehicle be disposed of?

Most States allow an abandoned vehicles to be removed by towing from your property. Laws vary but most allow towing and storage facilities to obtain a title after going through due process. This involves contacting the owner of record and lien holders and advertising the vehicle for sale.
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How can I calculate how much money I will save by going to a higher mileage vehicle?

To calculate fuel cost savings between two vehicles, use the AGCO Miles Per Gallon Savings Calculator. If you would also like to consider other factors of vehicle cost, when making a buying decision, the AGCO Vehicle Cost Calculator compares new vehicle cost to that of a used vehicle.
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How can I check my credit history before trying to finance a vehicle.

The Federal Fair Credit Reporting Act requires the major credit agencies to supply a free credit report to consumers once a year, upon request. This information can be accessed on line at

http://www.annualcreditreport.com/

or by writing to
Annual Credit Report Request Service
PO Box 105283
Atlanta, GA 30348-5283

It is also reported that there are several sites on the internet that advertise free credit reports and may not be legitimate. Never provide sensitive credit information without being certain with whom you are dealing.
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How does a pre-purchase vehicle inspection vary from a general inspection?

The pre-purchase vehicle inspection is far more investigative in nature. This is because the history of the vehicle is not known as would be the case with a general inspection. For instance evidence of previous collision damage, abuse, concealed damage and flood damage are looked for. With a general inspection, concealed damage is much less a concern and pending problems and maintenance issues would be more of an issue. Naturally there are also items common to both, such as looking for pattern failures, worn, leaking or damaged components.
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How long should I wait before I wax my new car?

Factory paint finishes, on new vehicles, can be waxed right away. The paint is cured at a much higher temperature than is possible with a re-paint. For best protection a new car should be carefully washed, prepared and waxed within the first month of ownership and at least twice a year thereafter.
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I agree with your stated position, new vehicles are terrible investments. Other than that is there an instance when you might recommend a new vehicle over a pre-owned vehicle?

The reason to buy a new vehicle is emotional. If a person just wants a new vehicle, and finances are not a problem, they should buy one. Life is too short not to have the things we want and can afford. Other than that, if a specific vehicle is needed and not available otherwise. The point is, a new vehicle is NOT something that is going to save a person money. Often a newer vehicle is not considered, even though it might make more sense. For instance, if too much is being spent on a present vehicle a NEWER vehicle may be in order, rather than a new vehicle.
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I am buying a new vehicle and trading in my old one. Is there a way to know if I am receiving a fair trade value?

Yes there is, simply go to the Links section of our web site and click on the “What is my used car worth (Edmond's)” link. Enter your vehicle make, model, mileage, options and condition and it will give the value adjusted for your local area.

Retail value is what a dealership might expect to receive when they sell the vehicle. Third party is what a person might expect to sell the vehicle for, if they sold it themselves. Trade-in is the value that might be expected when trading the vehicle with a dealership. Because the dealership expects to make money on the vehicle, trade-in will be much lower than retail price.
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I am buying a new vehicle I have been told by the salesperson I must have an extended warranty in order for the bank to finance the vehicle. Is this so or a scam?

No legitimate financial institution requires an extended warranty. More likely, getting the sales commission from the Extended warranties is the salesperson's primary concern. I would contact the insurance commissioner in your State and report this. Any dealership making such a claim, may violate the law.
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I am considering a Ford truck and would like to avoid one with the two-piece spark plugs that break. Is there a list of the models that came with two-piece spark plugs?

The two-piece plugs were used in the 4.6L, 5.4L and 6.8L 3-Valve engines; The two Valve engine does not use this plug.
FORD:

2005-2008 Mustang
2004-2008 F-150
2005-2008 Expedition, F-Super Duty
2006-2008 Explorer,
F-53 Motor home Chassis
2007-2008 Explorer Sport Trac

LINCOLN:

2005-2008 Navigator
2006-2008 Mark LT
MERCURY:
2006-2008 Mountaineer
For more information, please see our Detailed Topic, Ford Spark Plug Breakage.

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I am looking for a used vehicle and plan to have it thoroughly checked before buying. Are there any quick checks I can do to narrow my search?

First, would be determining what type of vehicle best serves your needs. There is a multitude of vehicles on the market and selecting one is a daunting task. Closely examine your needs, determine the vehicle(s) that best match them and concentrate on those. For instance, an SUV may be fine, but will not meet be a good choice for a high fuel mileage vehicle.

Once a particular vehicle, that meets your needs, is settled on, you need only find the best example of that vehicle. This is normally the vehicle that is least likely to have problems. Look it over carefully for signs of previous abuse. Mis-matched paint, body lines that do not line-up and scratches in the paint may show the vehicle has been wrecked and repaired. See our Detailed Topic Spotting Wrecked Vehicles for more information.

Also take notice of the brand of tires, battery and oil filter on the vehicle. When the tires and battery are premium products and the oil filter is the same brand as the vehicle manufacturer, good previous service is shown. These choices show the vehicle has been well maintained by someone that understands value. This is a vehicle I would consider having professionally assessed and buying.
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I am looking for a used vehicle and see the word “Certified” on many. These are normally more expensive than comparable vehicles. Is the certified vehicle worth more or is this merely marketing?

The word “Certified” has no specific meaning and no value in my opinion. Many times the vehicle has had some type of inspection and often has an extended warranty added to the price. It should be considered exactly the same as any other used vehicle. That is it should represent value and you should have it inspected by a third party before purchase.

I feel extended warranties are of no value and I would never pay additional to have one. The best “warranty” is a thorough inspection by a trained professional, to buy a vehicle that does not have problems.
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I am restoring an old car and need an all over paint job. Does changing the color of the vehicle lower the value?

The loss or gain in vehicle value, after a color change, depends on the vehicle and the target market. For instance, to a true collector, a T-model Ford painted any color but black would be worthless. Very high-end vehicles are also best left with their original color as the value will suffer. On less-expensive restorations, where originality is not as big an issue, a brighter color may actually enhance the value.
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I am thinking of buying a vehicle with a salvage title. Are there any special precautions I should take?

A salvage title indicates that an insurance company has determined the vehicle was not feasible to repair, based on its value. Insurance companies are expert in this field. If such a vehicle could be bought, repaired and sold at a profit, I would question the quality of the repair. At a minimum I would have the vehicle inspected thoroughly by an expert in the field. Keep in mind also, a lower purchase price can be quickly offset by the lack of resale value.

See our Detailed Topic Spotting Wrecked Vehicles for more information.
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I bought a car and did not get a title, because it could not be found.

Without a signed titled, that if free of liens and a bill of sale you will not be able to register the vehicle. Basically this means you do not own the vehicle and can be in violation of several laws by operating it. You should contact the owner immediately and have them file with the State for a missing title. The vehicle should not be operated until the title is obtained and it is registered. Your State department of motor vehicles can provide you a list of documents that will be necessary. If the title cannot be produced, the seller has no right to sell the vehicle. Return the car and ask for your money back. If the seller refuses an attorney might be able to assist you in getting your money back.
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I have a nine-year old vehicle, worth about $2500.00. The intake manifold is leaking badly and it needs other repairs amounting to about $2000.00. I like the vehicle other than that, would I be foolish to spend that much money on an old car?

I think the answer depends on your plans and the overall condition of the vehicle. If you like the vehicle I suggest having a full general inspection performed. This will let you know if there are other major problems pending.

If the vehicle is in otherwise good condition, this repair should allow you to get another year or two of service. At the end of that time, you could sell it and still get your money back. In its present condition, the vehicle is worth next to nothing. Buying a replacement will likely cost several times the amount of the repair. From that perspective repair may make sense.
For more information on deciding whether or not to repair a vehicle, please see our Detailed Topic, Should I Repair of Buy Another Vehicle.

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I have always driven American vehicles but I am considering a used Japanese import. I notice the oil pressure seems very low at an idle, compared to my other cars. Should I avoid this car?

It is always wise to have a professional check the vehicle before purchase. As a general rule, Japanese vehicles tend to run lower oil pressure than the American vehicles, particularly at idle. Some specify as little as ten pounds of pressure per 1000 RPM. This is lower than most American vehicles, but adequate to lubricate the engines designed to run this pressure.
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I intend to buy a used car and have a Car Fax report, do I still need to have it inspected?

Yes! Such reports are fine but can be very limited. The information comes from insurance companies and auto manufacturer warranty data. Not included are damage that is not repaired and damage that was not covered by insurance.

For instance a vehicle could be flooded and then put up for sale, with no insurance claim. This would not be reported, but should be found in a pre-purchase inspection. A few other things that would not show up include, a vehicle that has been severely overheated and not repaired. A vehicle on which the maintenance has been neglected. A vehicle that was wrecked and repaired without insurance being involved and so on.
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I just bought my first new car and wonder what is the best break-in procedure to follow?

Most new vehicles require little in the way of special break-in procedure. For the first 2,000 to 4,000 miles avoid rapid acceleration and hard braking. This allows the engine to "run in" properly and allows the brake pads to seat to the rotors. Also avoid driving at a set speed for a long period. It is better to vary driving speed during break-in. For instance instead of setting the cruise control on 70 MPH, try driving 60 for a while, then 65 and then 70. Repeat the cycle about every 15-20 minutes.

I also feel the initial oil changes should occur very quickly. For more information, see When should I do my first oil change,
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I like to save money and am considering a hybrid to cut my fuel cost.

If lowering cost is the objective, a hybrid may be a very poor choice. The design of hybrids are extremely complex with an abundance of very expensive components. For instance, a replacement battery can be over $6000.00. The hybrid motor may be $12,000 or more to replace.

More to the point is the cost savings. Even at $4.00 per gallon, driving 12,000 miles per year, going from 35 mpg (conventional high efficiency vehicle) to 40 mph (hybrid) would save only $171.00 per year. That equals less than $857.00 saving in five years not counting additional repair cost.

For even more information on hybrid vehicles, see our Detailed Topics article, Hybrid Hype.

A more detailed article on increasing fuel mileage is in our Detailed Auto Topics section under Saving Gasoline, Saving Money.
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I once sold a vehicle and the buyer did not transfer the title. Later I was contacted by the State because the vehicle did not show current insurance coverage and it took quite a bit to straighten out. How can this be prevented?

This can be a serious issue, especially if the vehicle becomes involved in an accident. Best is to remove the license plate before transferring the vehicle. Surrender the plate to the Department of Motor Vehicles in your State, along with a copy of the bill of sale. Forward another copy of the bill of sale to your insurance company and retain a notarized copy in your personal records.
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I purchased a used vehicle recently and the owner told me it was in very good condition. I did not have it inspected until after the purchase and have learned it needs over $2000.00 in maintenance and repair.

The Louisiana Redhibition law sometimes covers such things. Go to Links and click on that section for more details. A lot depends on the nature of the repairs to be done and if you paid close to retail price for the vehicle.

Maintenance items, though they can be very pricey are normally not considered a defect in the vehicle. An exception might be if you were told they were all up to date, and they were not. Also when a vehicle is purchased at a discounted price [far below retail] much more responsibility is shifted to the buyer, caveat emptor.

Haste is important, as the more time that elapses, the weaker the case becomes. Perhaps a phone call to the seller, followed by a letter is in order. If they fail to respond you can pursue the matter through the courts, with or without an attorney.
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I really like a vehicle I am looking at, but it has a Car Fax report of a serious collision. Should I avoid this vehicle?

I would advise a pre-purchase inspection of the vehicle, by a professional. Insurance companies often rate severity, on the amount spent, relative to the value of the vehicle. In reality, seriousness is a factor of how well the vehicle is repaired.

For instance, a vehicle could sustain a good deal of bolted-on part damage. All parts could be replaced and the repair might rate as serious because of the cost. However, such a vehicle might be as good as new.

Another vehicle could sustain structural damage with few parts needing replacement. The cost of repair may be far less, but the outcome could also be far less promising. A professional can measure the vehicle and inspect the repairs and give far better information.
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I recently bought a Ford vehicle with a key pad entry system on the door. I did not get the code when I bought the vehicle. Is there a way to find out what it is?

The key code is stored by the vehicle computer system and most shops are equipped with tooling that can retrieve it for you.
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I recently purchased a used vehicle and have since discovered it had been seriously wrecked and repaired improperly. I have had several problems relating to this. The seller wrote “As Is” on the bill of sale, is there anything I can do?

This sort of thing happens more often than you might imagine, and is a great reason to have any vehicle inspected before purchase. This may fall under the Louisiana redhibition law. This law, with some exceptions, states that a product has an implied warranty. This warranty includes the vehicle is fit for the purpose for which it was sold. A vehicle with collision damage and resulting problems may fall under the definition of not being fit for the purpose sold.

An attorney is not necessary to file under the law, however a consultation may be a wise investment. Many times the sale can be rescinded or the sales price reduced. It is important to act quickly as the case becomes weaker as time passes.

Check our Links section for a link on the Louisiana Redhibition Law.
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I suspect the vehicle I purchased might have been wrecked?

A well repaired vehicle might only be spotted by a professional, but it is not likely to be a big problem. Spotting poorly repaired vehicles is a lot simpler. Please read our Detailed Topic article Spotting Wrecked Vehicles for a photographic guide. If you are still in doubt a professional inspection might be a good idea.
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I would like to buy an American vehicle, any suggestions?

Best is to forget the name and do some research. Most vehicles people have come to accept as domestic may not be. Many imported names actually represent domestic built vehicles. For instance, according to the American Automobile Labeling Act (AALA) a US built vehicle would be built in the US and contain 75% or greater US content. A Toyota Camry built in Georgetown Kentucky would qualify. A Ford Focus could be built in Canada and contain around 67% US content and not qualify as a U.S. car.

Vehicles sold in the US are labeled as to US content and country of origin. This information should be on the vehicle or available from the selling dealership, though may not be prominently displayed.

For much more information on US built and imported vehicles see our Detailed Topic section.
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In general do the cars start breaking after 100K or 150K miles. I understand a lot depends of the kind of car and the maintenance done by the previous owner.

As you wisely stated, it depends a lot on the previous maintenance and care. As a general statement, years seem to be harder on vehicles than miles. High mileage, relative to age, normally means the vehicle has been driven a lot, which is good. I have serviced many Acura, Honda, Toyota and Lexus vehicles with well over double that mileage and very few problems.
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Is it better to buy a used vehicle from a new car dealer, a used car lot or an individual?

Each entity has, good and bad points. First remember that new vehicle dealers buy used vehicles from auctions the same as used car dealers. They can have all the same problems that any used vehicle can have and should be checked just as closely before purchase.

New vehicle dealers generally will command a higher price for their vehicles than used dealers or individuals. The advantage is they are normally large enough that if there is a problem, a legal remedy is effective. For instance, should a vehicle be found to have a major problem, a judgment in your favor is only as good as the ability of the seller to honor it.

There are several large independent used vehicle dealers. These can offer more security than some small dealers and still have lower prices than dealership lots. The time in business and reputation of the lot should also be considered.

When buying from an individual, you have the advantage of speaking directly to the owner of the vehicle. Eye contact, body language, etc. can give you a good “feel” for the person. Always ask open ended questions like, “Why are you selling the vehicle?” The price from an individual will usually be the lowest. A disadvantage is, if there is a problem, their ability to refund your money may be a concern. Never buy a vehicle without having it checked by a professional that you trust.
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Is it possible to tell if a vehicle has been wrecked and repaired?

A professional can almost always spot a vehicle that has been wrecked and repaired. Any repair performed so well as to be indistinguishable would present no risk to the buyer.
For more information, please see our Detailed Topic, Spotting Wrecked Vehicles.

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Is it wise to trade a vehicle after one year?

All vehicles suffer depreciation. This is the difference in value between new and used. The amounts vary somewhat from one vehicle to another, but all vehicles lose their maximum value in the first year. This can average around 28 to 30%. This combined with the sales tax and other fees paid adds to a substantial loss and an extremely high cost per month.

The affect of these losses taper off in time, because they are averaged over a broader duration. Our Vehicle Cost Calculator may help demonstrate this more clearly. As a general rule, it is far wiser to buy a three-year old vehicle and keep it for about ten years.
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Is there a better time of year to sell a used vehicle?

Certain type vehicles may sell better at different times. For instance four-wheel drive vehicles may be easiest to sell just before hunting season. Inexpensive, small vehicles tend to sell best before schools go into session and at tax refund time. Convertibles and sports cars sell best in the Spring. Overall, clean vehicles in good condition, sell almost any time of the year.

When selling a vehicle, I find it best to be totally honest with the buyer. I advise having the vehicle checked by a qualified mechanic before placing it for sales. This avoids unpleasant surprises and offers a bit of protection against future claims. Disclose any problems that exist, in detail and list them on the bill of sale.
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Is there a check-list (checklist) I can use when looking at used vehicles?

You can download and print the AGCO Auto check list, designed to help in inspecting used vehicles, by clicking this icon.

AGCO Auto Used Vehicle Check List
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Is there an easy way to determine the year model of a vehicle?

The tenth digit of the vehicle identification number or VIN represents the year of manufacture.

YEAR	CODE	YEAR	CODE	YEAR	CODE	YEAR	CODE
1980	A	1990	L	2000	Y	2010	A
1981	B	1991	M	2001	1	2011	B
1982	C	1992	N	2002	2	2012	C
1983	D	1993	P	2003	3	2013	D
1984	E	1994	R	2004	4	2014	E
1985	F	1995	S	2005	5	2015	F
1986	G	1996	Y	2006	6	2016	G
1987	H	1997	V	2007	7	2017	H
1988	J	1998	W	2008	8	2018	J
1989	K	1999	X	2009	9	2019	K

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Lease payments are less than payments when purchasing a new car. Can I save money with a lease?

The payments are lower because you are not gaining equity in the vehicle. For instance, at the end of the lease term, you surrender the vehicle with nothing to show. With a purchase, you own the vehicle when the payments are finished. This can be a tremendous savings if the vehicle is well maintained. Most well maintained vehicles last ten or more years with minimum problems. This is equivalent to driving with no vehicle payments for several years.

Even greater savings can be had by purchasing a three year old vehicle rather than new. Because of depreciation, three year old vehicles can often be had for half or less than the price of new.

If you would also like to consider other factors of vehicle cost, when making a buying decision, the AGCO Vehicle Cost Calculator compares new vehicle cost to that of a used vehicle.
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Looking at a used car, the owner will not let me test drive it because of liability if there were an accident. What can be done?

Laws vary from State to State, but his concern is legitimate. Having the owner drive while you ride and observe may determine if the vehicle is worth pursuing. If so, have the owner bring the vehicle to a shop that you trust and that performs pre-purchase inspections. Legitimate shops carry insurance that protects the owner in case of an accident.
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Looking at new cars, I noticed several have miles on the odometer, up to 200. How many miles can a vehicle have and still be considered new?

Laws vary from one State to another. Federal odometer law normally defines a new vehicle as having 300 or less miles. Another condition is that the vehicle has not been licensed to a retail customer. Usually, seven to ten miles are normal, accounting for servicing the vehicle and test drives.
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Looking for a used Japanese vehicle, is there anything particular to watch out for?

As with any vehicle the type of service and maintenance [or lack of] the vehicle has received will largely determine future problems. The easiest way to verify this is with a thorough inspection by a professional, trained in this type of work.

Another thing to consider is many Japanese vehicles use timing belts that normally need replacement between 60,000 and 105,000 miles. If this has not been done, it is wise to factor the expense into the price paid for the vehicle. Done properly, this can be an expensive repair, sometimes costing over $1000.00 on certain models. A proper inspection will give you this type of information.

In recent years, the move has been away from timing belts and toward timing chains, particularly on Toyota and Honda. Timing chains can last much longer than belts and may help lower maintenance cost. This may help justify the extra cost of a later model vehicle.
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My car has been on the market for several weeks. A few people have looked at it but nobody seems to want to buy. Are there any tricks to selling a car?

Certain things can increase your odds. First the vehicle must be reasonably priced for the mileage, age and condition. Checking our Links Section, follow the link to How Much Is My Car Worth. Price the vehicle at or near the private seller amount and be honest about the condition.

Selling a vehicle is similar to selling a house, or anything else. Curb appeal is important. The vehicle should be clean, inside and out. Professional detailing is often a good investment. Be certain to remove all personal items before showing the vehicle. Also make sure the vehicle is running well and everything works. Copies of the service history will also add value.

I also find, listing the price, with the vehicle saves a good deal of time. If you are willing to negotiate, state that as well. Listen to the potential buyers carefully. If you listen, they will normally let you know why they are not willing to buy. If possible, offer to remedy whatever concerns them and see if they will buy. Finally, politely ask for the sale. People often respond when the salesperson lets them know they really want to sell the vehicle.
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My car has overheated and I am told the head gasket is leaking and the price of repair is well over a thousand dollars. Should I consider repair or buy another vehicle?

There are at least three major considerations.

1.) Does the vehicle meets your needs?
2.) Do you like the vehicle?
3.) After this repair is the vehicle likely to be in good condition?

If the answer for any of these questions is NO, it may be time to look at another vehicle.

Economically speaking, if the vehicle serves your needs and after the repair you can expect several more miles of service, repair is likely your best option. The sales tax on a new vehicle can easily exceed the amount of this repair. Even a used vehicle will normally cost several times the cost of this repair.

Our Buy or Keep Calculator is designed to help you make just such a decision.
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My car only gets 25 MPG, how much can I save trading for one that gets 35 MPG or more?

The savings depends on the amount you drive and the cost of fuel. Most folks average 12,000 miles per year. With fuel cost at $5.00 per gallon moving from 25 MPG to 35 MPG would save $686.00.00 per year. Unfortunately this savings may be more than offset by the generally much high cost of maintaining newer vehicles.
To calculate fuel cost savings between two vehicles, use the AGCO Miles Per Gallon Savings Calculator.

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My Father and I are looking for an old vehicle to restore. Any pointers?

Having restored several old vehicles, I have learned a few lessons. Buy a vehicle, of the type you want that is in the best condition you can find. Every dollar spent buying a very good condition vehicle is likely worth ten dollars trying to repair one in poor condition. This may also have the added benefit of a vehicle that is immediately able to be driven. It is a lot easier to keep your enthusiasm for a vehicle you can drive than one that is in pieces. Vehicles that were popular, such as a 1955 Chevrolet, 1965 Mustang or a 1969 Camaro will be much easier to find parts for. Lastly, mechanical repairs are normally less expensive and more easily accomplished than body repair.
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My present vehicle runs well but only averages about 20 mpg. Some new vehicles get about 30 mpg. How can I tell how much I will save?

There are several online calculators on the AGCO website that will help you calculate such cost. Using the miles per calculator, if you drive the average 12,000 miles per year and fuel cost $4.00 per gallon, your savings would be $800.00 per year.
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My vehicle has almost 100,000 miles and I have done nothing but change the oil. I am starting to have problems with it. Should I buy a new vehicle?

It would have been better to have maintained the vehicle from earlier on, but it is not normally too late to reverse a lot of potential problems. I would start with a good General Inspection. This will let you know where you are, in reference to where you should be. Bringing all maintenance up to date at this point may allow several years of additional use. For more information please read, the life cycle of a vehicle.
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My vehicle is about 8,000 miles out of the manufacturer’s warranty and I have a transmission going out. The dealership says there is nothing they will do, what is my recourse?

A warranty is a contract with a specific term agreed to by both parties. When the term expires the contract has been honored. In some instances, the manufacturer may be willing to help. Contact the Zone Manager, listed in your owners manual. You are not likely to prevail in a legal suite but an attorney could advise best on that possibility.

For future reference, the AGCO End of Warranty Inspection can often spot things like this and can be a great investment.
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Recently I bought a forty-year old car that has been sitting idle for twenty-five years. The car is in excellent condition and I would like to restore it.

If you have the knowledge, time, tools, a place to do the work yourself and you enjoy doing it, vehicle restoration can be an enjoyable hobby. If you have to pay someone to restore the vehicle or do not enjoy the work, it can be a very large chore. A vehicle of that age, that has been sitting idle for that long, is likely to have a multitude of issues. When vehicles sit idle, dry rot, corrosion and age combine. Bearings start to pit, seals get hard and start to leak, hoses dry rot and metal components corrode.

A good starting point would be to get it running. I would drop the fuel tank and dispose of any fuel. Check to make sure the tank and pump are not rusted. If they are they need to be replaced. If not add fresh fuel, a new battery, change the oil and see what happens. If it runs, I would next replace all fluids, including coolant, transmission fluid, brake fluid, power steering fluid and so on. The tires will also need to be replaced and the brakes and suspension should be thoroughly checked.

Very likely when the vehicle is operated, other problems may show up. Air conditioners are prone to leaks and the transmission and differential may need to be addressed. It would be best to prepare for a long and expensive project.
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Should a person ever consider buying a vehicle with 100,000 or more miles on it?

High mileage vehicles can offer a substantial cost savings. Mileage is best considered in reference to the age and service reputation of the vehicle. For instance, a two year old Toyota with 100,000 miles would not scare me at all. The high mileage is almost certainly the result of long trips, which is excellent for the vehicle. A 12 year old vehicle with 100,000 miles is a totally different matter. The combination of years and miles would likely put this vehicle much closer to the end of its service life.

Service reputation is the average life (without major repair) of a given make and model. Certain makes simply do not hold up as well as others. This is where a good relationship with a service shop is invaluable. A professional technician can advise you on the average service life of different vehicles you are considering.
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Should I consider a hybrid vehicle?

The fuel cost savings on hybrids appear to be greatly exaggerated. The saving in fuel cost is very unlikely to offset the additional price asked. Combined with potentially extremely expensive repair cost, I feel hybrids are a very unwise investment.

For even more information on hybrid vehicles, see our Detailed Topics article, Hybrid Hype.
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Should I consider an extended warranty when buying a vehicle?

Extended warranties are notoriously bad investments. They are also one of the top profit centers in some dealerships. The salesperson and the dealership normally receive a hefty commission for selling these policies. Far better and much less expensive is a sound maintenance program. Maintenance prevents problems, rather than paying a large fee in advance to cover them. Here’s an article with much more detail.
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Should I consider buying the car at the end of the lease?

Adding the lease payments to the price asked for the vehicle will render a total cost. This is normally much higher than if the vehicle had been purchased outright. This is a good reason not to enter a lease in the first place, but the lease payments are now gone. Buying a lease should be considered the same as buying any other used vehicle. If the price asked is right, at least you know how the vehicle has been cared for.
For more information please see our Detailed Topic, Problems With Automobile Leasing.

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Should I consider purchasing a vehicle with a salvage title?

Salvage on a vehicle title indicates the vehicle has sustained damage not economically feasible to repair. This is a huge red-flag and a warning of possible problems. The cost difference between it and a non-salvage vehicle may not be enough to cover the loss of resale in the future, and the risk assumed. I would advise against such a purchase.
For more information on salvage vehicles, please read our detailed topic, Buying a Vehicle With a Salvage Title.

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Should I have all problems with my vehicle repaired before placing it for sale?

This depends on the level of vehicle being sold. On late model and expensive vehicles, buyers tend to expect everything to be in first class shape. A needed repair can be a major deal-breaker on such a vehicle. On older, inexpensive vehicles this is less of a factor. Sometimes a buyer would prefer a better price to everything working perfectly. A low price may be more important than air conditioning.

At least, all safety items must be in good repair and the vehicle should be as clean as possible. Remove all personal items, clean the interior and exterior. I also find honesty is the best policy. I advise having the vehicle checked by a qualified mechanic before listing it for sale. Fully disclose, in detail, any problems you know of and repair needed problems as above. This may help prevent unpleasant surprises and possible future legal action.
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There are a few minor problems with my vehicle. Should I fix them before trying to sell?

A lot depends on the age and price of the vehicle. The newer and more expensive the vehicle, the more people will expect everything in working order. On older, inexpensive vehicles a buyer may be willing to accept minor problems. A vehicle with everything working does not always bring a top price, but it is always easier to sell.

Another approach is to disclose fully the problems and discount the vehicle by the amount of the repair needed. This can work if the problems do not affect the safety of the vehicle. Most States have laws requiring the vehicle to be in a safe operable condition. Before listing the vehicle, have an inspection by a professional automotive technician. This may protect you as well as the buyer and may add value to the vehicle as well.
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To raise cash, I need to sell my late model vehicle and buy one for around $5,000. I need to get two years service to allow my finances to recover.

Vehicles in your price range will need to be either several years old or will have high-mileage. Of the two choices, a later model with higher mileage is the better choice. Years are normally much harder on a vehicle than miles. High mileage on a later year model generally means a lot of highway type driving, also easier on a vehicle. Toyota and Honda products are generally very reliable, even with high mileage as long as maintenance has been kept up to date.
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What does Blue Book value of a vehicle mean?

Blue Book was a brand name of the Kelly Company, who listed used cars with their values. This was often used by banks and loan companies, before online services, to determine the value of vehicles for financing. The name is sometimes improperly used to describe many car valuation services. Today there are several companies and web sites that provide used car valuation.
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What does the word salvage on a vehicle title indicate?

Salvage on a vehicle title indicates the vehicle has sustained damage not economically feasible to repair. This is a huge red-flag and a warning of possible problems. The cost difference between it and a non-salvage vehicle may not be enough to cover the loss of resale in the future, and the risk assumed.
For more information on salvage vehicles, please read our detailed topic, Buying a Vehicle With a Salvage Title.

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What is considered an antique or classic car?

The word antique is very subjective. A generally accepted definition is something reminiscent of an earlier period and valued for its age. Clearly this is very non-specific. Under Louisiana law a vehicle twenty-five years old and in original condition is eligible for an antique vehicle license plate.

The term classic may be even more subjective. Generally a classic is a vehicle design that routinely might command a price above what would otherwise be considered normal given the age and condition of the vehicle.
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What is my used car worth?

There may be at least three answers. There is a dollar figure based on average resale price. This figure is available online, in books designed for the purpose and can be seen in local want ads. This number is used when trading in a vehicle or when borrowing money based on the vehicle value.

There is also what the vehicle is worth to you. Sentimental value, cost of replacement and so on add into this figure. This amount is important when judging the overall cost of driving. The final value is what someone able to buy the vehicle is willing to pay. If selling the vehicle is the goal, this may be most important.
For more information on deciding whether or not to repair a vehicle, please see our Detailed Topic, Should I Repair of Buy Another Vehicle.

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What is the difference in a title and a vehicle registration?

The registration certificate establishes that the vehicle is properly registered. It normally comes with the license plate and is renewed when the plates are renewed. It must be kept in the vehicle and shown to law enforcement personnel when requested. The title proves ownership of the vehicle and should never be kept in the vehicle. The title is issued when the vehicle is sold and list the owner[s] and any lien holders. The title is only amended when ownership changes or a lien is satisfied and released.
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When buying a used vehicle is it better to look for an older low mileage or a newer vehicle with higher miles?

Other factors being equal, years are harder on a vehicle than miles. For example, I would rather have a two year old vehicle with 50,000 miles than a six year old vehicle with 20,000.

Vehicles are designed to be driven and higher miles often shows the vehicle was operated on the highway as opposed to in town. Highway miles are normally much easier on a vehicle than stop and go driving in town.

Other quick checks include looking at the type of tires on the vehicle and the type of oil filter and battery. I find a vehicle with low grade tires, oil filter and battery has normally not been well maintained. In any case, never consider buying a vehicle with out having it checked by a profession, that you know you can trust. AGCO offers a very thorough pre-purchase inspections service.
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When is it time to consider buying another vehicle?

If you like the vehicle and it meets your needs, I think cost of maintenance is the determining factor. Cost normally depends on the past maintenance the vehicle has received. On my vehicles, I track monthly repair cost. When repair cost average exceeds $200.00 per month, I feel it is time to change. For instance I may go three months with no repair and then spend $450.00. Since this averages $150 per month I feel okay.

When faced with a large repair I have to consider the time it will last. For instance, if I need to spend $2000.00. Can I reasonably presume that if I spend this, I can drive ten months with no repair cost? If the answer is yes, it’s a fair investment. If the answer is no, I feel it is time to change.

Our Buy or Keep Calculator may help you make just such a decision.
For more information on deciding whether or not to repair a vehicle, please see our Detailed Topic, Should I Repair of Buy Another Vehicle.

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Which new car is the best from an investment standpoint?

No new vehicle is good, from an investment position. Most lose 50 to 65 percent of their value in the first three years. Some are not as bad as others, depending on several factors. The major sellers, Toyota and Honda for instance are major sellers for a reason. A lot of people like them and continue to buy them. Vehicles that are not popular in a given area are usually represent more problems. For instance, Subaru is popular in the Northeast and West. In the South, there are few sources of parts or service. This may make them very problematic, if there is an unexpected breakdown.

Companies that are financially weak or are divisions of companies that are financially in trouble can be a real problem. Should the company fail, warranties may end, parts will be far more problematic and resale value may evaporate?
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While under warranty, is it best to have maintenance performed by the dealership?

I believe the opposite. A dealership may be less likely to inform you of things that can be addressed by warranty. Having a good independent shop keeping an eye on things may be in your best interest. An independent shop can help you in obtaining warranty work, by documenting problems. Your warranty is also preserved, when an independent shop performs your maintenance.

See our Detailed Topic article Maintaining New Vehicles for more details.
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Why are the interest rates on a used vehicle higher than on a new one?

Many finance companies and banks feel the risk of non-payment may be higher with a used vehicle and use this as a reason to charge additional interest. Higher rates should not automatically be accepted, as everything is negotiable. Careful shopping is in order as the rates may vary greatly depending on the institution and personal credit history.
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Oil, Lubricants and Gasoline

After an oil change, I noticed 5W20 was installed in my vehicle that calls for 5W30 motor oil. Is this a problem?

Where 5W30 is specified, only it should be used. The 20 in 5W20 indicates the SAE rating for hot viscosity. A 20 weight oil is lower in viscosity than the 30 weight oil specified. This means the oil is much thinner at 100 degrees Celsius, operating temperature for most engines. The proper oil should be installed before the vehicle is driven.

A possible exception would be certain Ford products. Ford has revised the specification on many of their engines. The original specification was 5W30 but has been revised to 5W20. If this is the case, using 5W20 is perfectly acceptable. Ask the oil change facility if there is a reason they installed 5W20 and if your Ford vehicle falls into the category where it is recommended.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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After having my oil changed I noticed a spot under my vehicle. It seems to be coming from the drain plug, but I checked and it is tight. Why would a tight drain plug leak?

The threads on a drain plug do not seal. Only pipe threads that are tapered can form a liquid tight seal. Instead, most oil pan drain plugs have a seal washer or O-ring. The seal is under the head of the drain plug and is the actual seal. If the O-ring is worn or damaged or if the seal is crushed or omitted, the oil drain plug will leak.

A more detailed article, on oil drain plugs, is in our Detailed Auto Topics section under Stripped Oil Pans and Plugs.
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Are high performance air filters, that use oil on the element, worth the money?

The original equipment filter, supplied by the OEM manufacturer is usually the best overall choice. Air filters do NOT increase fuel mileage. From that respect, the high performance filters are no better. Other problems include time required to maintain (clean and oil) the high performance models. If oil gets on an air flow meter it can quickly be ruined. We remove so called performance filters frequently after replacing air flow meters.
For more information, please see our Detailed Topic When Should Air Filters Be Replaced.

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Can grease fittings be added to my suspension that does not have them?

Possibly, but I would advise against it. Most modern suspension components are designed to not have grease added. This is for good reason. One of the leading causes of failure in suspension and steering components was improper lubrication. Excessive lubrication ruptured the protective seals, causing rapid failure. Perhaps worse, the excessive grease sometimes found its way onto braking components, ruining them as well.

Modern components, without grease fittings are pre-lubricated with synthetic grease. These last far longer and give far less problems than the older components that could be greased.
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Can I increase fuel mileage by driving slower?

Driving slower and accelerating easier will make a major increase in fuel mileage on most vehicles.
For more information, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.

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Can I increase fuel mileage without replacing my vehicle?

Fuel mileage can almost always be improved some. The first thing is to make certain the engine is running the best it can. Address any “check engine” light immediately and have the tune of the engine checked about every 30,000 miles.

Engine temperature has a drastic affect of fuel mileage. If the vehicle has a gauge, be certain it is all the way into the normal range. An engine running below temperature will waste a lot of fuel. Tire pressure and wheel alignment also affect fuel usage, but to a much smaller extent. Tires should be inflated to about 10% under the tire makers maximum for best fuel mileage.

Driving habits have the largest affect on fuel mileage. Fast starts and stops waste a lot of fuel. Also driving at higher speed requires a lot more fuel to travel the same distance at lower speeds. Driving 68 mph rather than 72 mph may save 3-5 miles per gallon.

A more detailed article on increasing fuel mileage is in our Detailed Auto Topics section under Saving Gasoline, Saving Money.
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Can I safely extend the oil change interval on my vehicle if I use synthetic oil?

My answer would be no, for the following reasons. Synthetic oil is tougher and lubricates better than conventional oil. From a standpoint of breakdown, it is capable of protecting the engine for a longer period. It also cleans the engine better than conventional oil. Synthetic oil gets as contaminated and perhaps more so than non-synthetic oil.

One important function of engine oil is to remove and suspend contaminates that enter the engine. Solid contaminates, above a certain size, are removed by the oil filter. Liquid contaminates and smaller solids [40 microns or less] can pass through the filter. These contaminates may cause sludge, wear and corrode engine surfaces. They are removed when the oil is properly changed.

Synthetic oil offers many benefits, but extended oil change intervals do not represent overall lowest cost, in my experience.

A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.
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Can I substitute 10W30 oil for 5W30 oil?

Substituting oil viscosity is inadvisable. In an engine that calls for 5W30, there would be no benefit in switching to 10W30. Both oils are equivalent to 30 weight at 100 degrees Celsius. The 5W30 simply provides better flow at low temperature than 10W30 with equal protection at operating temperature.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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Can I use automatic transmission fluid in my power steering or must I use power steering fluid?

Some manufacturers recommend automatic transmission fluid or ATF and other manufacturers recommend differing types of power steering specific fluids. Ford, Chrysler and Toyota have recommended ATF in several models. GM normally recommends power steering fluid. Honda and some others have a specific fluid they recommend. I always install what the manufacturer recommends. Even the most expensive specialty fluids are very inexpensive, when compared to the cost of a hydraulic failure in a power steering system.
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Can I use regular 5W30 instead of dexos in my 2011 and up GM vehicle?

Dexos is not an oil. Dexos is an oil specification issued by General Motors for their vehicles. Standard 5W30 will not likely meet this specification and can cause engine problems not covered by the GM warranty. Most oils that meet and exceed dexos, like Mobil One, will be synthetic or at least synthetic blends. The safest bet is to use a product approved under dexos unless you can be sure it meets or exceeds the specifications.
For more information, please read General Motors dexos oil in our Detailed Topics Section.

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Do diesel vehicles get better mileage than gasoline powered vehicles?

All other factors equal, diesel will provide better fuel mileage than gasoline. This is because diesel fuel contains more oil [energy] per gallon. Diesel engines also run at much higher compression ratios. With more compression the fuel/air mixture will explode more violently, releasing more energy.
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Do high performance air filters increase fuel mileage?

Air filters do not increase fuel mileage. Even a badly clogged filter will NOT lower fuel mileage. As the air flow is decreased the fuel that is added is also decreased and fuel mileage will remain constant. This is not to say air filters should not be changed. A dirty or clogged filter may affect performance and may get sucked into the air box, allowing unfiltered air to enter the engine.

A more detailed article on increasing fuel mileage is in our Detailed Auto Topics section under Saving Gasoline, Saving Money.
For more information, please see our Detailed Topic When Should Air Filters Be Replaced.

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Do I have to buy dexos oil from a GM dealership?

The dexos license is sold by General Motors to oil producers. Any manufacturer that buys their license can provide approved oil. GM enforces this by stating it may void the warranty if licensed oil is not used. Not all oil producers are willing to pay GM for the license. Best is to look for the dexos logo or contact the oil company to see if they are licensed.
For more information, please read General Motors dexos oil in our Detailed Topics Section.

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Do you recommend any engine oil additives?

I have seen no evidence that oil-additives offer any benefits over quality oil without additives. No vehicle manufacturer or oil company that I am aware of recommend their use and I agree. The highest quality oil available (API classification) should be used and it should be replaced frequently. If extra protection is desired, consider changing to synthetic oil. Check Should I switch to synthetic oil, for more details.
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Does engine oil evaporate?

In general, almost no oil is lost due to evaporation. There are certain volatile components that can be lost if left exposed to air over time. In an automobile engine this is almost imperceptible and will not account for a significant amount of oil.
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Does mixing regular oil with synthetic oil damage my engine?

Different brands of oil, whether conventional or synthetic, use different additive packages. For this reason, I feel it is better to stay with a single brand of oil. As long as the additive packages are compatible, mixing conventional and synthetic oils should cause no damage.

A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.
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Does Summer driving require thicker engine oil?

Summer temperatures are not a consideration as all engines operate far in excess of ambient temperature. To an engine that operates near 100 degrees Celsius, there is no difference in a mild Spring or the hottest summer day. Cold Temperatures are much more of a concern, as the engine must be lubricated on startup. Thicker oil does not flow well at low temperature.

This is why manufacturers specify multi-viscosity oil, capable of handling a wide range of conditions. For instance, 5W20 has the same flow characteristics as five-weight oil at zero degrees Celsius and the protection of 20-weight oil at 100 degrees Celsius.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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Does the octane rating of gasoline have anything to do with quality? Can an engine designed for 87 octane benefit from 89 or 93 octane fuel?

Octane rating and the quality of the gasoline should have no correlation. Many modern vehicles will give better performance and sometimes better economy with a higher octane fuel. Higher octane allows engine timing to be run at a slightly higher rate. Whether the additional cost of higher octane fuel is justifiable would take some experimentation.
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How do I accurately check my fuel economy?

The most accurate way is on a long trip where you will use multiple tanks of fuel. Start with a full tank and record beginning odometer reading. When refilling, fill the tank until the first time the nozzle cuts off. Record the odometer reading and the number of gallons used. Repeat this on each fill up.

When finished again fill the tank until the first cut off and again record the miles. Now with a little math you can record total mileage. Simply subtract beginning miles from ending miles for total miles traveled. Then add total gallons used. Divide total miles by total gallons to get miles per gallon.

The more miles driven the more accurate the calculation, as this will average minute differences in fill amounts. By recording driving conditions for each segment [mountains, high speed, cold weather, etc.] you may also determine the affect each type driving has on your vehicle mileage.
For information on increasing fuel mileage, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.

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How often should I change my oil?

The answer depends on the manner in which the vehicle is operated. Most manufacturers widely advertise very long [7,000 to 15,000 mile] intervals. They also state under severe conditions oil should be changed much more frequently.

The conditions that constitute severe service may surprise many people. For instance, if the average drive is less than ten miles, the vehicle may be considered severe service. Stop and go traffic may be considered severe service. Sitting at traffic lights with the engine idling and vehicles that do not get driven every day, are also very hard on engine oil.

Driving every day, for long distances, is very easy on oil, and longer intervals may be okay. If most driving is short trips and stop and go, my experience is that 3,000 mile changes are much more cost effective, considering the possible consequences.

A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.
For more information on changing oil, please see our Detailed Topic How to Change Your Motor Oil.

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I accidentally put 93 octane fuel in my vehicle that calls for 87.

If the engine does not require the higher octane fuel, it simply will not be used. This should have no real affect on the engine. Using 87 octane where 93 octane is required is a different matter. This can lead to pre-ignition [valve clatter, ping] and quickly cause serious damage.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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I do my own oil changes. A friend said I should fill the filter with oil before installing it, to help get oil into the engine faster?

The danger is, any debris that enters the filter, through the outlet hole, will not be filtered and will go straight into the engine. Oil, even from a sealed container is not always perfectly clean. Best is to use an original equipment filter, quality oil and let the oil flow through the filter, by filling the crankcase.
For more information on changing oil, please see our Detailed Topic How to Change Your Motor Oil.

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I drive about 500 miles a week, mostly highway. How often should I change my oil?

Highway driving, for longer distances at a time, is very near ideal conditions for oil. The engine is at full operating temperature and running at peak efficiency under this type use. Under these conditions longer change intervals are possible and any quality oil will work just fine. Three-month change intervals should be adequate under these conditions.

A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.
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I have a Buick with 29,400 miles. It is making a buzzing sound on acceleration and driving. When you slow and stop, the buzzing slows and stops. If it helps, the buzzing started after I had an oil change and air filter change last week.

Check to see if the noise can be duplicated with the vehicle sitting still and in park. If the noise is still there, I would first suspect it is related to the filter replacements. If not the noise is more likely related to the suspension or drive line.

If the noise can be duplicated sitting still, it could be the air filter housing was improperly installed and is now rubbing on an engine drive pulley. A defective air filter can also cause a similar noise.

First check the installation of the air filter and see if it is a genuine Delco replacement. If not, temporarily remove the air filter and see if the noise goes away.

If it does not, check the oil filter and again see if it is a genuine Delco replacement. A restricted oil filter can cause the oil pump to buzz as the oil bypasses the filter.

Some times quick-lubes, franchises and even some dealerships and independent shops use inexpensive aftermarket parts that can cause such issues. AGCO recommends and installs only genuine Delco filters on GM vehicles.

We also install only genuine OEM replacement filters on any make we service. For instance, Toyota filters on Toyota, Honda filters on Honda, Motorcraft filters on Ford, etc.

A more detail article, on oil filters, is in our Detailed Auto Topics section under All About Oil Filters.
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I have a clear, oily fluid under my vehicle, what could it be?

Many fluids used in automobiles have dye added for identification. There are also several that are clear. Power steering fluid is one of the more common clear fluids. There is sometimes also a noise when turning the steering wheel with a power steering leak. Brake fluid also appears clear, though it is actually slightly amber in color. Brake fluid leaks often appear at the wheel area or under the master cylinder. A lower than normal brake pedal and a brake warning light may also be present.

Engine oil that is very clean may also appear to be clear. This is common after an oil change and can indicate a leaking oil filter or drain plug. Oil that is spilled on the engine, may appear as a leak, sometimes days later. Other possible sources are a leaking shock absorber, rear differential fluid and leaking air conditioner refrigerant oil.
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I have always used a certain name brand oil in my engine. The last time I was in the parts store the salesperson told me they have a less expensive private label oil, made by the same company. Should I consider switching to the less expensive oil?

Checking with the manufacturer of the oil you mentioned, I was told the private label is manufactured by the brand name company. It was stated they are similar but not the same product. Further it was stated the name brand exceeded API (American Petroleum Institute) standards and the private label meets them.

AGCO sells nothing but brand name lubricating oils, selected for their lubricating characteristics. I would use nothing else in my personal vehicles.
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I have just purchased a new vehicle and wonder when I should do the first oil change? I have heard several opinions and would like yours if you don’t mind?

If maximum engine life is the primary concern, I would do the first oil change at 500 miles. I would then change again at 1,500 miles and every 3,000 miles thereafter. When an engine is manufactured there may be a good deal of debris that escapes the cleaning process. These frequent initial changes help address this issue.

Changing the oil and filter on a new engine at 500 miles, allows much of this debris to be removed early on. The second change is for additional safety and optimum results. It is also important to use a high quality oil filter capable of removing at least a 40 micron particle. The original equipment manufacturer’s filter will always meet this standard and is what we install and recommend.
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I have some old Mercon transmission fluid and was wondering if it will work in my truck that calls for Mercon-V?

Mercon is a brand name used by Ford for their transmission fluids. The original Mercon fluid is a conventional fluid, roughly equivalent to Dexron. Mercon-V is a synthetic based fluid. Mercon-V could be used in place of Mercon, but not the other way around. Mercon does not meet the specifications of Mercon-V and should not be substituted.
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I notice the abbreviation API followed by SN on my oil, what does this mean?

API stands for the American Petroleum Institute, one group that classifies oil. The two letter rating starting in the 1920's with SA, “S” meaning Service or passenger car and light trucks. The SA rating was plain mineral oil without any additives. As oils improve so do there classification. SA became SB and then SC and so on. SL came into being around 2001 and early in 2005 SM was introduced. Offered in late 2010 the SN rating is the latest standard of the API.
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I recently bought a new vehicle that calls for 5W20 motor oil. That seems awful thin in this hot climate. Would 5W30 be better?

Modern engines use oil for many things other than just lubrication. Engine oil often operates variable valve timing, displacement on demand and has an affect on catalytic converter life. The best oil is that specified by the manufacturer, 5W20 in this case. If lubrication is a concern you may consider switching to a synthetic oil.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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I saw an advertisement for pills you can add to your gasoline to increase mileage. Do these really save gas?

I have seen no evidence that such products do any good at all and they may even be harmful to your vehicle.

See our Detailed Topic article Wasting Money and Not Saving Fuel for far more details.
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I was told by my mechanic that I was greasing the suspension on my car too much. I usually grease all the fitting at every oil change (3000 miles). Is this too much?

Over greasing can be a problem. The additional grease tends to accumulate and attract dirt. This dirt often ends inside the part if fittings are not cleaned properly before lubricating. Excess grease may also rupture the seals on parts allowing severe contamination and allowing grease to find its way onto brake components.

Proper lubrication involves cleaning the fitting and then stopping before the bellows, on the part, starts expanding. Synthetic grease is very durable, once every third oil change is normally sufficient.
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I was told the automatic transmission fluid in my Honda is not the same as other cars, is this true?

Honda vehicles should use only Honda brand ATF-Z1 or equivalent automatic transmission fluid. Honda ATF-Z1 fluid is a Dexron base but contains additive and friction modifiers required by the Honda transmission.
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Is adding a can of fuel injector cleaner to my vehicle, now and then, a good idea, or is it just another scam?

I advise against routine use of injector cleaner in fuel systems. It is not necessary, as injectors are self-cleaning. Repeated doses of high detergent may also erode the protective coating on the injector tips. With flex-fuel vehicles it may also adversely affect the flex-fuel sensor. It may also damage the fuel tank, as most tanks are now made of a plastic material.
When injectors become clogged badly enough to require cleaning [rare] we use a system that bypasses the fuel system and feeds the chemical directly into the fuel rails. This avoids running cleaner through the tank, fuel pump, sensors and lines.
Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.

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Is brake fluid the same as power steering fluid?

Brake and power steering fluids are totally different and must never be substituted. Brake fluid is generally an alcohol based fluid. Power steering fluid is generally a petroleum based fluid. Petroleum will rapidly destroy the seals and rubber components of a brake system. Brake fluid on the other hand, will not lubricate the power steering system and will quickly promote corrosion in the system.
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Is conventional engine oil recommended for vehicles used in hot regions?

Ambient temperature is not much of a factor in oil selection. Engines routinely operate above 200 degrees Fahrenheit, far greater than any ambient temperature. If there are concerns, synthetic oils resist heat better than conventional oils. Unless synthetic oil is otherwise recommended for the engine by the manufacturer, conventional oil will hold up in hot regions.
It should also be noted if high ambient temperature causes the engine to run hotter, it may be considered severe conditions. Severe conditions call for more frequent oil change intervals.
A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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Is it bad to put non-recommended oil in your car?

Yes, in modern vehicles, engine oil does far more than just lubricate the engine. There are variable cam timing mechanisms, hydraulic tensioners, displacement on demand and several other things that use engine oil. There are also many other factors, such as the affect of crankcase oil on catalytic converters, cold start lubrication, fuel mileage and so on to consider. Manufacturer’s take these and many other factors into account when specifying the proper engine oil. The vehicle manufacturer’s recommendation should be followed for best results.
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Is Mobil1 5W30 approved for use in 2011 and up General Motors vehicles that call for dexos?

As of this writing Mobil1 is licensed under the dexos specification and can be used in 2011 and up GM vehicles.
For more information, please read General Motors dexos oil in our Detailed Topics Section.

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Is the oil filter sold by the maker of my vehicle the best one to use?

The word “BEST” could depend on a great number of factors. For instance there are filters which can remove smaller particles [micron rating] than the original equipment manufacturer (OEM) part. This might be considered best under some circumstances. The problem is, such a filter may restrict oil flow or clog prematurely.

There are many factors to consider in oil filter performance. The OEM does a good over-all job in this category, and I feel they are the best choice for most people.

A more detail article, on oil filters, is in our Detailed Auto Topics section under All About Oil Filters.
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Is there a way to look at a fuel filter and tell if it needs to be replaced?

I am not aware of any way to look at a fuel filter and judge its condition. The flow rate could be tested, but since the filter would have to be removed, it would not be cost effective. Since most fuel filters are inexpensive and relatively easy to replace, they are normally replaced based on mileage and performance.

I have found, when a fuel filter appears to be old, asking the client when it was last replaced works pretty well.
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It is time to pack the wheel bearings on my truck. Is there any problem changing to synthetic grease when packing bearings?

Synthetic grease will give great service with your wheel bearings. Thoroughly clean all the old grease with a clean solvent. Allow the bearings to dry and then pack them with the synthetic product. As always, replace any wheel seals and lubricate the seal surface with a light coating of grease as well.

Please see our Detailed Topic article Adjusting Wheel Bearings for far more details.
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My car calls for 5W30 oil and this seems very thin for the hot climate I live in. Would 10W30 be a better choice?

Both 5W30 and 10W30 have a hot viscosity of 30 weight. The 5W30 adds the advantage of being able to respond like a 5 weight oil at cooler temperature. It can also improve fuel economy and lower emissions. I do not recommend substituting a non-approved oil in any vehicle.

If temperature extremes and operating conditions are a concern I would recommend switching to a synthetic product of the same viscosity. Also more frequent change intervals will help a great deal with viscosity concerns. Please, look in the Oil, Lubricants and Gasoline section under Should I switch to synthetic oil, for more details.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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My car has started to use oil, should I switch to a heavier viscosity?

I feel the same viscosity, recommended by the manufacturer for new vehicles, is good for the life of the engine. Thicker oil will not help oil consumption. It may make it worse. Thicker oil stays on the cylinder walls longer and may result in additional consumption. Add to this the problem of raised oil volatility damaging the catalytic converter. Best is to stay with the recommended oil and simply change it a bit more often.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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My car manual recommends I use 5W30 oil, would you still use the recommended type even when the car has high kilometers and is over ten years old?

Yes, the same viscosity will work well for the life of the engine. I feel it is a misconception about thicker oil and older engines. Thicker oil tends to boost oil pressure, which is not needed or desirable. At the same time it puts more oil on the cylinder walls which can increase oil consumption. Another problem is, oil drain-back. Thicker oil cannot drain to the pan as fast. On older engines with oil passages possibly restricted this may be an issue.
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My Chevrolet calls for dexos1 oil, is this the same as viscosity?

The dexos specification refers to a license, purchased by oil producers, and not actual viscosity of the product. At this time all General Motors gasoline powered vehicles, using dexos1 have an equivalent SAE viscosity of 5W30.
For more information, please read General Motors dexos oil in our Detailed Topics Section.

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My owners manual says I should change my oil every 5 month or 5,000 miles. I drive about 2,000 miles every five months. I do not understand why I should change the oil with only 2,000 miles of usage. Does oil go bad in five months time?

Two-thousand miles in five months, means short trips or lack of use. Short trips are severe service for an engine and greatly increases sludge and acid buildup. Under these conditions moisture tends to build up in oil. This forms the acids and sludge, which pass through the oil filter. Under these conditions, I suggest even more frequent changes, without regard to mileage.

Best would be to drive the vehicle more, particularly on longer trips. This allows the heat of the engine to boil off much of the moisture.

A more detail article on change interval is in our Detailed Auto Topics section under The Sad Truth.
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My power steering fluid was low and the pump was making noise. I added fluid and the noise went away, but after I turned off the engine, the fluid came pouring out the reservoir opening.

The fluid level getting low indicates a leak in the system. Low fluid, allows air to enter the system and produce noise. When fluid is added, the air is pushed into the system and compressed by the fluid pressure. When the pump quits turning the pressure drops and the compressed air expands. When the air expands the fluid is pushed out. First locate and repair the leak. Once the leak is repaired, filling and bleeding the system of air, should cure the problem.
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My truck is equipped to run on flex-fuel. If I switch to E-85 will my fuel mileage go up, down or stay the same?

Ethanol produces about 33% less energy per gallon than gasoline. Switching to 85% ethanol will result in a 28% drop in fuel mileage. For more information, please see our Detailed Topic, Ethanol Fuel, Good or Bad?
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My vehicle calls for 0W20 motor oil which seems awful thin. An internet forum makes a compelling argument that 5W30 would provide much better lubrication.

Engine oil today does far more than lubricate the engine. It must also operate variable cam timing, hydraulic tensioners on timing chains, resist high temperature viscosity shear and not damage the ultra-expensive catalytic converters. All these things and more must also be optimized over a wide range of temperatures. Deciding on the proper viscosity for engine oil is a very delicate balancing act. OEM engineers design and test the engine under an immense number of conditions. Their recommendation takes far more factors into account than even petroleum experts have access to. To avoid unforeseen problems, the manufacturer’s recommendation should always be followed.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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My vehicle calls for premium 93 octane fuel. Can I substitute regular fuel?

Engines that specify premium fuel use higher compression than other vehicles. Compression is roughly the amount the fuel/air mixture is “squeezed” before being ignited in the engine. The more the mixture is compressed [high compression] the more power is produced when it is ignited. This makes high compression engines more powerful than lower compression models and also makes the use of high octane premium fuel necessary.

Octane slows the burning process and prevents engine damage. With high compression engines and low octane fuel, the fuel/air mixture may explode before the ignition fires. When this occurs, the piston is being forced to travel upward by the crankshaft, while the combustion process is driving it down the cylinder. This phenomenon is also know as detonation, pining, valve rattle or valve clatter. Severe engine damage may quickly occur. Only high octane fuel should be used in engines that specify its use.

For more information on valve clatter see our article Valve Clatter, Spark Knock, Pinging and Pre-ignition.
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My vehicle has 160,000 miles and the U-joints have started to squeak. There are no grease fittings in the present joints. Should I replace the joint with the type that has a grease fitting?

To allow a U-joint to be greased, there must be leakage at the seals. This leakage allows the old grease to escape, when new grease is added. This is okay, if the joints are lubricated every 5,000 miles or so. This is very inconvenient and often neglected. Without lubrication the joint will quickly fail.

With the sealed universal joint, nothing gets in or out and they normally last 150,000 plus miles with no service. I would recommend using the exact non-lubricating type joints.
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My vehicle has about 50,000 miles and I am interested in switching to synthetic oil.

Synthetic oils are much tougher and much better at cleaning an engine than conventional petroleum products. The synthetic oil will go to work to clean any sludge buildup that was present in the engine. Any sludge that is broken up will need to be filtered out. This may restrict an oil filter very rapidly. I recommend oil filter replacement within 1,500 miles after switching from conventional to synthetic oil. After oil filter replacement the oil should be topped off as needed.

For optimum engine life, synthetic oil should still be replaced at 3,000 mile intervals, unless the average trip is over 20 miles. Many synthetic oil producers recommend longer change intervals and the product is capable of longer life. The problem is, synthetic oil gets just as contaminated as regular oil, perhaps more so. Changing the oil is the only way to insure removal of a lot of these contaminates.

A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.
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My vehicle has been stored for about a year and I am concerned about the gasoline in it. Should I add fuel stabilizer before I try to start it?

Fuel stabilizer works when added to fresh fuel, before it is stored. It will NOT rejuvenate old fuel, and no additive will help. Best would be to drain the tank, dispose of the old fuel and fill with fresh, before starting. If not, you might try to dilute with fresh fuel, drive until half empty, refill and repeat several times in rapid succession.
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My vehicle has never used oil until I recently had an oil change. I have had to add oil twice (1000 miles) since the change. What could have happened with just an oil change?

You did not mention any leakage. A loose oil filter or drain plug can cause quite a bit of oil to be lost. Assuming no leak, changing from the brand of oil that has always been used sometimes causes oil consumption. The additives in different oils are sometimes incompatible. This can result in oil usage. Best is to return to the original brand of oil and see if the problem starts to subside.

Another possibility would be an internal engine problem. Though this is not likely, some type of failure could have coincidentally occurred around the same time. If the oil was drained and the engine inadvertently started, without adding oil, it may not be coincidental.
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My vehicle is not driven every day and I only put about 6,000 mile a year on it, mostly very short trips. Can I change my oil once a year?

Not being drove is very hard on an engine and so are short trips. This type of use is normally considered extreme service and the change recommendation for extreme service would apply.

When an engine is started, the temperature begins to rise. Within minutes it will rise to 180 degrees Fahrenheit, or more. When turned off and allowed to sit, the engine cools. Heating and cooling may cause moisture to condense in the crankcase.

Moisture attacks internal engine components and may turn to sludge. Moisture also passes through the oil filter. Moisture is removed when the oil reaches and exceeds 212 degrees Fahrenheit. At this point it turns to steam and is drawn out of the engine by the crankcase ventilation system. Unfortunately, with short trips this does not occur.

I suggest changing to synthetic oil under these driving conditions. I would also recommend going no more than six months between oil changes, even with synthetic oil.

A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.
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My vehicle list a specific automatic transmission fluid, is this just marketing or should I use only the recommended fluid?

Many vehicles have a specific fluid recommendation. Among these are Honda, with their own fluid, Ford with several versions of Mercon, and Chrysler products. Often fluids are formulated with specific additives to address concerns in the design of the unit. AGCO does not substitute from the recommended fluid.

For more information, see our Detailed Topics article, Properly checking transmission fluid.
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My vehicle manufacturer says that the automatic transmission fluid does not need replacement, unless I tow a lot. I do not tow, it has 155K miles and has never been changed. Change or leave it alone?

Manufacturer's realize the odds of problems from improper service, are greater than the odds of problems from no service at all. The wrong fluid, not enough fluid, the wrong filter or a filter not properly installed will ruin a transmission. Their recommendations are based on this and a supposed service life of 100,000 miles.

With proper service, a transmission will last longer. Lack of service may cause failure from a plugged filter, debris and depleted fluid. For a transmission with no service for 155,000 miles, any damage that will be done has likely already begun. While it cannot hurt, I see little advantage to servicing the transmission at this point.
For much more on proper transmission service, please see our article Transmissions and proper service.

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My vehicle says synthetic oil should be used. Is this the same as 5W30?

No, synthetic refers to certain standards that the oil must meet regarding load capacity and many other factors. It does NOT mean what the oil is made of and is not the same as viscosity, which is resistance to flow. The expression 5W30 is a viscosity rating from the Society of Automotive Engineers or SAE. The five is the low-temperature viscosity, W means winter use is acceptable and 30 is the high-temperature viscosity. Only oil listed as synthetic should be used in vehicles that specify synthetic and the proper viscosity should also be used.
A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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Recently an oil change shop told me my engine was full of sludge and should be flushed. I have no symptoms, should I be concerned?

Engine flushes are one of the more popular wallet flushes sold. Chemically flushing engines is not recommended and can cause harm in many instances. A far better procedure is to use the natural detergent in oil to clean the engine, changing the oil and filter at short intervals and several times. For instance changing the engine oil and filter at 1,500 mile intervals, three times, will help remove buildup and will never harm the engine.
Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.

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Should I have the fuel injectors on my car cleaned to improve my gasoline mileage?

Routine cleaning of fuel injectors are unnecessary and will not improve fuel mileage. Any quality brand of fuel contains detergents and injectors are designed to self clean. We see few cases of injectors that need cleaning. Even with dirty injectors we find, the symptom is normally rough idle and not poor mileage.

A failed injector, stuck open or closed could reduce mileage, but would likely not be helped by cleaning. Buying quality fuel is a better investment. If mileage is below normal for the vehicle, having the fuel management system checked would be a better idea.

Please see our Detailed Topic Fuel Injection and Wallet Flushing for more information.
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Should I switch to synthetic Oil?

Synthetic oil is much tougher and much better at cleaning an engine than conventional petroleum products. If the engine has any sludge buildup, the synthetic oil will go to work to clean it. Any sludge that is broken up will need to be filtered out and this may restrict an oil filter. I recommend the oil filter be replaced within 1,500 miles of switch from conventional oil to synthetic.

For optimum engine life synthetic oil should still be replaced at 3,000 mile intervals, unless the average trip drove is 20 miles or more. Many synthetics oil makers state longer change intervals and the product is capable of longer life. The problem is synthetic oil gets just as contaminated as regular oil, perhaps more so. Acids and other liquid contaminants can build up in oil and changing the oil is the only way to insure removal of a lot of these contaminates.

An additional issue is, if there are any leaks that were being masked by the sludge, they may be revealed by the cleaning.

A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.
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Should I try to find fuel without ethanol for my vehicle?

Ethanol is not without drawbacks, but modern vehicles have very few problems using E-10 or 10%. If the vehicle is designed to run higher percentages, as with flex-fuel, the biggest drawback is a loss of fuel mileage. Even antique vehicles can run on E-10, with proper retrofitting. Many fuel stations that advertise 100% gasoline, are unbranded. I prefer E-10, from a high-volume, name brand station, to a private label 100% gasoline. For more information, please see our Detailed Topic, Ethanol Fuel, Good or Bad?
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Should I use high-mileage formula oil in my older vehicles?

The oil originally specified, by the vehicle manufacturer, is the best oil for the life of the vehicle. I feel high mileage oils come more from the marketing department than engineering. With oil, as with anything on the vehicle, lowest cost is obtained by preventing rather than trying to repair problems. Using the oil specified by the manufacturer, the OEM oil filter and replacing it on a regular basis will prevent problems. There is nothing in high mileage oil that will undo damage from previous neglect.

For more information on oil change intervals read our article The Sad Truth and for more on oil filters read All about oil filters.
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Should power steering fluid ever be replaced?

Power steering fluid acts as a hydraulic fluid, seal conditioner, coolant, cleanser and lubricant to the system. As such, it is subjected to quite a bit of deterioration and the additives are depleted over time. There is also the high cost of replacing steering gears and pumps to consider. I recommend replacement between 50,000 and 100,000 miles.

Many manufacturers do not add power steering fluid replacement to their maintenance schedules. I believe this is due to a short-sighted attempt to make maintenance costs appear lower. To the vehicle owner I think overall lowest cost is far more important.

Power steering fluid is easily replaced by simply drawing the old fluid from the power steering reservoir and adding replacement fluid. It is not necessary to remove all the old fluid as dilution and repeating the process a few times is very adequate. Also be aware that different vehicles have different type power steering fluid recommendations.
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Should the lubricant in the rear differential be replaced?

All lubricants benefit from periodic replacement. Additives become depleted over time and debris suspended by the lubricant becomes a problem. This is a particular problem where there is no filter, such as the rear differential.

Under normal driving, I recommend the differential oil be replace between 50,000 and 100,000 miles, with the recommended lubricant. When towing it should be replaced more often. It might also be a wise investment to convert to synthetic oil, if your vehicle does not already use it. Also be aware that many limited slip differentials require additives or special oils.
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Since new, I have used synthetic oil in my vehicle. On the last oil change the dealership accidentally put regular oil in it. I have heard this will damage my engine.

It is best not to change the brand of oil, conventional or synthetic, as additive packages vary. Some are not fully compatible with others. For instance changing from Exxon to Castrol or vice versa. Changing from synthetic to conventional oil is the same. As long as the additives in each are compatible, there will be no damage. Even if not, slight oil consumption for a period of time is normally the worse symptom.
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The fuel mileage on my Toyota has really dropped lately. I’m down about eight miles per gallon from the mileage I was previously getting. The check engine light is not on and I see no apparent reasons for the decrease.

Eight miles to the gallon is a substantial drop. Many things can contribute. Since the check engine light is not on I would check to see if the engine is getting to full temperature. An engine with a stuck thermostat may run far below normal temperature and this will drastically affect fuel mileage.

Also the sensor that reads engine coolant temperature (ETC) should be checked. Failure of this sensor to read correctly will disturb the output of the engine computer. The computer will mix more fuel per air volume for an engine it thinks is below normal temperature. It may also not allow the transmission to shift to overdrive, also decreasing mileage.
For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.

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The fuel mileage on my vehicle is lower when my wife drives it than when I drive it. How can this be?

Driving style is one of the largest factors in the fuel mileage received. Different driving habits can increase fuel mileage up to five miles per gallon, on certain vehicles.
For more information, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.

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The owner's manual of my 2011 General Motors car says use only dexos1 oil. Is this a new type of oil?

Dexos is not a product at all, rather a license that oil producers must buy from GM in order to be approved. The dexos license requires oil to pass specific test. GM claims specific properties tested for are necessary in their automobiles.
For more information, please read General Motors dexos oil in our Detailed Topics Section.

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What do the numbers and letter like 10W30 mean with regards to oil?

The W stands for Winter which means the oil is acceptable for all seasons. The ten reflects the cold properties of the oil and 30 the hot properties. For example 10W30 oil can flow like a ten weight oil when cold (0 degrees Celsius) but still offer 30 weight protection when hot (100 degrees Celsius.)

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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What does the word weight mean in relation to engine oil, like five weight oil?

Weight is a scale used by the Society of Automotive Engineers or SAE to classify viscosity characteristics of lubricants. Viscosity is resistance to flow at a given temperature. A low weight, such as five, will flow much faster at a given temperature than a higher weight, such as seventy-five. Temperature must be considered as oil tends to flow more slowly when cold than when hot.

Viscosity is often measured in centistokes (cSt) which is roughly, the time it takes a fluid to flow through a given sized orifice at a given temperature, often 40 degrees Celsius. SAE five weight oil is roughly equivalent to two centistokes.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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What happens if I over fill my engine oil?

Over filling oil is a matter of degree. With one quart or less it is unlikely to cause a noticeable problem. If more oil is added the level rises, the crankshaft will begin to pull oil up and whip it into a vapor. This will be drawn into the PCV system and can cause damage to the catalytic converter(s) and increase oil consumption.
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What is the best engine oil?

There is no best engine oil, instead there are many specifications various oils meet that make them proper for a given engine. The Society of Automotive Engineers or SAE, the American Petroleum Institute or API and others insure oil meets the proper specifications. What is best for one vehicle may not work in another. The best oil is the oil that meets or exceeds the specifications of the manufacturer of the vehicle. Brand is less important than selecting the proper product. Most major oil producers sell products that meet manufacturer’s specifications as long as the proper product is selected.
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What is the difference in 5W30 and synthetic oil?

These are two different matters entirely. The 5W30 is a Society of Automotive Engineers or SAE viscosity rating. Viscosity is basically a resistance to flow or similar to how thick the oil is at a given temperature. Synthetic concerns certain quality characteristics of the oil. For example, a product can be 5W30 and synthetic, synthetic blend or conventional oil.

A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.
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What will happen if you put E-85 fuel into a standard gas motor?

If the vehicle is not designed to run on E85, the check engine light normally comes on, due to excessive lean condition and the vehicle will lose power. Some vehicles may quit running, others may run very poorly. In one case we saw a fuel pump ruined, possibly the same affect as running out of gas? Continuing to run the wrong fuel can cause permanent damage, much like running the engine too lean.
For more information on fuel pumps and why they fail, please see our Detailed Topic, What Causes Fuel Pumps to Fail.

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Where can I dispose of engine oil?

Best is to locate a recycle center in your area. Virtually all used motor oil is recycled, most to make heating oil. Many oil change shops and some parts stores will take used oil for recycling. Some municipalities also have centers set up for the purpose. A call to the local Department of Environmental Quality should provide a list of local recycle facilities. Never mix anything with used motor oil as this can make it hazardous and not acceptable for recycling.
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Where does the engine oil go when the dipstick is low?

Engines generally lose oil in two ways. Oil may leak pass the piston rings or valve guides and be burned in the engine. If excessive, this requires engine repair to correct. Oil may also leak externally, due to bad gaskets and seals. There will normally be evidence of such leakage, such as oil under the vehicle or a burning smell.
Losing a small amount of engine oil is considered normal by many manufacturers of vehicles. They contend that proper lubrication requires a small amount of oil leaking passed the piston rings. This will normally account for one quart of oil or less in about 2,000 miles of driving. Losing more oil may be considered a problem and should be investigated.

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Which engine oil should I use?

Selecting the proper engine oil can be complex. Fortunately, all vehicle manufacturers have done the hard work and recommend specific oils for their vehicles. The owner’s manual will list the proper oil for the application. If the owner’s manual is not available, a specification guide for the vehicle can often be used. Be cautious of any recommendation by a dealership, oil change or repair shop that is not the same as the manufacturer recommends.
A more detailed article on oil viscosity is in our Detailed Auto Topics section under Oil Viscosity.

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Why did Ford revise the specification on the engine oil in many of their V-8 engines from 5W30 to 5W20?

The lower viscosity oil provides better fuel economy and may be easier on the catalytic converters. Ford also felt 5W20 provides more than adequate lubrication for the engines specified.
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Why do mechanics wipe off the oil dipstick and then put it back in before taking an oil level reading?

When the engine is running, oil is slung around inside the crankcase and onto the dipstick. This could result in an incorrect reading. By wiping the dipstick clean and reinserting it, a more accurate level of oil is displayed. The engine should also be allowed to sit without running for two minutes before taking a reading. This allows more of the oil circulating in the engine to return to the oil pan and gives a more accurate reading.
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Why does driving faster burn more gas?

Gasoline is energy and energy is required to overcome inertia and friction. The faster a vehicle is driven the more energy, in the form of gasoline, is required. Modern vehicles also learn the way they are driven. More aggressive driving will change shift points and engine tune and will consume more fuel to increase power output.
For more information, please see our Detailed Topic, Driving Tips for Better Fuel Mileage.

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Why is synthetic oil not recommended for older engines?

There is no reason synthetic oil cannot be used in an engine, regardless of mileage. Different brand oils use different additive packages and switching brands of oil, whether synthetic or conventional can lead to oil consumption. That aside, with well maintained older engines there should be no problem whatever. With engines that have not been well maintained, the detergents in synthetic oil can remove crud that is temporarily concealing oil leaks, and reveal leakage.
When changing to synthetic oil I have also found it is wise to replace the oil filter, about halfway through the change cycle. This may help prevent any sludge that is being removed by the synthetic oil, from plugging the oil filter. For instance, replace the oil with synthetic, drive 1,500 miles and replace the oil filter. Top off the oil and then replace oil and filter at the normal change interval.
A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.

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Why would engine oil turn milky brown in color?

The most common cause of milky-brown engine oil is coolant contamination. This can result from leaking intake gaskets, blown or leaking cylinder head gaskets, a cracked cylinder head or even a bad radiator or engine oil cooler. The situation is very serious as even a very small amount of coolant destroys the ability of engine oil to protect the engine. Very quick diagnosis and repair are mandatory to prevent engine damage.
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Will it hurt my engine to temporarily mix petroleum with synthetic oil?

Surprisingly, petroleum can and often is labeled as synthetic in the United States. The word synthetic has been found to be a marketing term, relating to certain characteristics, and not what the oil is made of. While I don’t advocate mixing different brands of oil, because of additive differences, what is labeled synthetic and conventional oils are compatible. Other than additive differences they can be mixed without damage to the engine.

A more detailed article on synthetic oil is in our Detailed Auto Topics section under Should I Use Regular Or Synthetic Oil.
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Radiator and Cooling System

A friend told me about a chemical that can be added to the radiator to make my engine run cooler.

It is not possible for a chemical to lower engine temperature on a modern vehicle. Temperature is extremely important and regulated closely by the engine computer. The thermostat and cooling fans control the temperature within a narrow range. If temperature starts to drop the thermostat closes, blocking coolant flow and the fans are switched off. If temperature is higher than normal, there is a problem. The problem should be diagnosed and corrected before driving.
For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.

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A friend told me it was improper to pour antifreeze into the radiator and then add water. Instead, he said it should be premixed before pouring it in. Why would it not just mix in the engine?

Your friend is correct. Antifreeze weighs about 9.3 pounds per gallon at room temperature. Water weights about 8.3 pounds per gallon at the same temperature. The much heavier antifreeze will settle to the lower part of the engine block. There is little circulation in that area and proper mixing is not likely.

Without premixing, it is difficult to judge that equal portions of water and antifreeze are being added. Even if equal parts of antifreeze and water are added, they may not be distributed properly. This can result in the corrosion and freeze protection being seriously diluted, in the upper parts of the system.

See our Detailed Topic Dexcool, coolant and proper service for even more information.

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A hose busted and my engine over heated. I quickly added cool water to bring the temperature down. The next day I noticed the water pump was leaking badly.

Water pumps can easily be damaged by overheating and by thermal shock, adding a cool liquid to a hot system. Best is to let a hot engine cool naturally and only after cooling, add the proper coolant and distilled water that has been premixed.
For more information, please see our Detailed Topic, Preventing Water Pump Problems.

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A shop told me the thermostat is making the engine in my car run too cold, but my heater works fine. Is this just a ripoff?

The term cold may be a poor choice on the part of the shop. To an engine, 180 degrees Fahrenheit is considered cold. This is because most engines are designed to run at around 195 degrees and higher. If the vehicle is OBDII, 1996 or newer, it may set a check engine light for this problem. While 180 degree coolant will easily warm the passenger compartment, it can cause harm to the engine. Fuel may not be properly atomized at this temperature and the computer may request a much richer fuel-air mixture. Lower engine temperatures may cause lower fuel mileage and can contribute to wear and engine sludge buildup.
If you are not sure about the shop, why not get a second opinion? Here’s an article on finding a great shop in your area.
For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.

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After 130,000 miles, the radiator hose on my vehicle started to leak at the clamp. I tightened the clamp, and it still leaked. I tightened it more, and the clamp broke. I replaced the clamp and now all is okay. Is this a defective or worn-out clamp?
It is not probable that a hose clamp would wear out, nor last 130,000 miles if it were defective. More likely, the rubber in the hose is starting to deteriorate, and the clamp is loose for that reason. Tightening the clamp, until it broke did not fix the problem, so more clamping force does not seem the answer. I would check the hose more closely for signs of deterioration.
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Are premixed antifreeze/coolant a better choice than concentrate and mixing my own?

Often premixed coolant is better than concentrate. Premixed coolant eliminates two large problems, improper mixing and the use of water with chemical and mineral contaminates. The drawback is a much higher cost and not all types of coolant being available premixed.

Tap water may contain many contaminates detrimental to a cooling system. Chlorine, fluoride and silica are just a few. This problem can also be prevented at a much lower cost by using distilled water. The coolant and distilled water must also be properly premixed, before putting into the system. A 50/50 mix is adequate for most applications and the coolant and water must be mixed thoroughly, before pouring into the radiator.

Please also see our article on cooling system leaks and proper service.

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At what mileage should I replace my coolant?

Deterioration of coolant is a chemical reaction and occurs over time. Mileage has much less of an affect. With most coolant, reserve alkalinity is nearly depleted in three years, with little regard to mileage. This means the pH is at or near 7.0, which is neutral. As the pH falls below 7.0 the coolant becomes acidic and starts attacking the metal components in the system. Using pH or time as a guide is much more reliable than mileage alone.
Please see our Detailed Topic Dexcool, coolant and proper service for even more information.

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At what temperature is an engine considered to be overheating?

Most modern vehicles use 195 degree Fahrenheit thermostats and operate close [10 degrees] to that temperature. Slight variances are to be expected, due to gauge differences and engine conditions. Some engines are also more tolerant than others as far as damage from overheating. As a very general guideline, temperatures over 225 degrees are normally seen as cause for concern and temperature over 245 may cause damage.
For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.

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Can a bad catalytic converter cause my radiator to overheat?

A bad catalytic converter can become plugged and severely restrict the exhaust. This can cause an engine to overheat as well as other problems.
For more information on please see our Detailed Topic, Catalytic Converters Problems.

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Can a bad head gasket cause my radiator to break?

Head gaskets fail in many different ways. If the gasket fails between a water passage and a cylinder, the coolant pressure may rise considerably and break the radiator among several other things. Radiators also just fail in time. Simple test are available to confirm the problem.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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Can a bad radiator cap cause overheating?

A bad radiator cap may cause overheating and corrosion to the system as well. The boiling point of coolant is raised by adding pressure to the system. Radiator caps are designed to hold this pressure up to a pre-designed point. When they leak, pressure is lowered and the boiling point of the coolant is lowered as well.

In addition the cap prevents evaporation, spillage and helps prevent air from entering the system. When air enters a cooling system corrosion is greatly increased. Corrosion can quickly eat through a radiator making the problem much worse. Radiator caps can be easily tested and should be replaced at any sign of a problem.
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Can a car with a blown head gasket still be driven?

It is highly inadvisable to operate a vehicle with a blown head gasket. Hydrocarbons enter the cooling system and can cause extreme corrosion. Excess pressure may also occur and can over-pressure the system, causing cracked radiators and other damage. Beyond that, the engine will normally have an overheating problem, causing additional damage. Like most problems, it will be far less expensive to correct if you do not procrastinate.
Please also see Symptoms of a Blown Head Gasket for far more detail.

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Can a lower temperature thermostat, for instance 180 degree in place of 195 degree, prevent overheating?

A lower temperature thermostat will not help with overheating, assuming the original thermostat was working. A 195 degree Fahrenheit thermostat will be fully opened at normal operating temperature and have no affect on overheating. Opening at a lower temperature only causes full flow sooner. If an overheating problem exist, the vehicle will continue to overheat. To fix the symptom of overheating, the cause must be found and rectified.
For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.

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Can a radiator cap cause my cooling system to over-pressurize?

The radiator cap is simply a pressure release mechanism. It can release pressure but not create pressure by itself. Too much pressure in the cooling system is often the result of engine cylinder pressure entering the cooling system. Common causes include a cracked cylinder head or leaking head gasket.
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Can a radiator cap test good and still cause problems?

The most common test of a radiator cap is the pressure test. The cap is attached to a fixture, pressure applied and the cap passes if it holds the stated amount of pressure. This is ONE test of a radiator cap but tests the lower seal and spring only. It is common for a cap to pass this test and still cause problems.

There is also a top seal that seals the cap to the system and a vacuum valve that allows the cap to vent and still seal. These must be tes

ratio of concentrate to water	Freeze point (Fahrenheit)
1 to 1	-49 degrees
1 to 2	-13 degrees
1 to 3	zero degrees
1 to 4	10 degrees
1 to 5	14 degrees
1 to 10	26 degrees

% Antifreeze	Freeze Point Fahrenheit
10%	25 degrees F
20%	16 degrees F
25%	10degrees F
30%	4 degrees F
35%	-3 degrees F
40%	-12 degrees F
45%	-22 degrees F
50%	-34 degrees F
60%	-48 degrees F
65%	-62 degrees F

AGCO Automotive Vehicle Questions Page