General Automotive
QUESTIONS
  1. A control solenoid has failed on the EGR system of my vehicle. Is this dangerous? Are poisonous gasses being released?
  2. 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?
  3. A friend convinced me to add gas treatment to my vehicle. I accidentally dropped the cap down the filler pipe. Will it cause damage?
  4. 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?
  5. 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.
  6. After replacing the battery, my car would die at idle. After a while it now idles okay again.
  7. An extended warranty company insists on putting aftermarket parts on my vehicle. Is this legal?
  8. Are dealership service departments free to interpret TSBs, leaving out parts as they see fit?
  9. At higher speeds, when I accelerate my engine clatters. If I down-shift, and RPM comes up, the clatter goes away.
  10. 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?
  11. Can a bad head gasket cause my engine to misfire?
  12. Can a bad PCV valve cause my engine to miss?
  13. Can a leaking valve cover cause a P0300 code?
  14. Can a rusty gas tank cause the fuel pump to keep going out?
  15. Can a serpentine belt with no cracks be bad?
  16. Can changing a serpentine belt cause the timing belt to break?
  17. Can I increase my fuel mileage by turning off the engine every time I stop, such as at traffic lights?
  18. Can I put windshield washer concentrate in my vehicle without diluting it?
  19. Can I tell if the timing belt on a vehicle has been replaced?
  20. Can running my fuel tank low really damage my fuel pump?
  21. Could a plugged catalytic converter cause a rear main seal to leak?
  22. Do all Ford V8 engines have the two piece spark plugs that tend to break when removed?
  23. Do cracked cylinder heads cause the radiator to over pressure?
  24. Do I need to have the wheel bearings on my vehicle serviced?
  25. Does a blown head gasket cause oil in the cylinders?
  26. 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?
  27. 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?
  28. How can I adjust the idle on my car?
  29. How can I adjust the idle speed on my vehicle?
  30. How can I tell if the intake is leaking on my GM vehicle?
  31. How long do spark plugs last?
  32. How much does it cost to change valve cover gaskets?
  33. How much injector cleaner is too much?
  34. How often should I pack the wheel bearings on my vehicle?
  35. How often should my fuel injectors be cleaned?
  36. 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.
  37. 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.
  38. 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.
  39. I have a fluid all over the inside of the left rear tire of my Suburban. What could be leaking in that area?
  40. I have a Ford with the two piece spark plugs. Is there anything I can do?
  41. 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.
  42. 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?
  43. I have a very old vehicle with a carburetor and the engine is misfiring. How can I find out what is causing the problem?
  44. 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?
  45. 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?
  46. 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?
  47. 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?
  48. I have an older vehicle which I have not maintained well. It has some problems now and I wonder if it is worth fixing?
  49. 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?
  50. I have had several fuel pumps fail in one year, any ideas?
  51. I have had to repair three of the power windows on my vehicle. Why so many problems?
  52. I hear a squeaking noise coming from the instrument panel of my Chevy Silverado. The noise stops when I switch the truck off.
  53. 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?
  54. 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?
  55. I replaced my catalytic converter and twenty thousand miles later it is bad again. Why would the converter continue to fail?
  56. I replaced my tires with larger sizes and now my speedometer appears to be off. Is this possible?
  57. I suspect the catalytic converter on my vehicle is going bad, what are the normal symptoms?
  58. 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?
  59. I was told the rear main seal on my engine is leaking. Why does it cost so much to repair?
  60. If I accelerate without downshifting my engine clatters. If I down-shift, and RPM comes up, the clatter goes away.
  61. If the accelerator on a vehicle sticks, what is the best thing to do?
  62. In what order are cylinders of an engine numbered?
  63. Is a valve cover gasket and a head gasket the same thing?
  64. 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?
  65. Is it helpful to power wash an engine?
  66. Is it possible to have a blown head gasket if I have never over heated my engine?
  67. Is it true that continuing to drive with a bad catalytic converter can damage my exhaust system?
  68. Is there a lubricant that will help valve clatter on acceleration?
  69. Is there a simple test for a broken timing belt?
  70. Is there a simple test to check a power window motor?
  71. Is there an additive that will stop a rear main seal leak?
  72. Is there an easy way to check the accuracy of my speedometer?
  73. My battery cables keep getting corroded. I clean them and a few months later they are corroded again.
  74. 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?
  75. 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?
  76. 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?
  77. 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?
  78. 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?
  79. My engine feels like it is not getting gas. Could this be the fuel pump?
  80. My engine has over 100,000 miles. Should I replace the timing chain?
  81. My engine is leaking oil at the valve covers. Is this a problem?
  82. My engine size is listed as 3.0L, what is the equivalent size in cubic inches?
  83. 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?
  84. My GMC Sierra has a cracked cylinder head and loses coolant. Is it safe to drive as long as I maintain the coolant level?
  85. My mechanic says I should let my engine warm up before driving. Is this right and for how long?
  86. My older Dodge Neon has a large puddle of coolant under the engine and will not start, any ideas?
  87. My timing belt was replaced and now I have a squeak noise. Could the belt be loose and slipping?
  88. My Toyota 2.4L engine has a timing chain. At what mileage should I consider replacing it?
  89. My truck intermittently stops running. A friend suggested I should replace the fuel pump.
  90. 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?
  91. 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?
  92. 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?
  93. My vehicle is slightly (5,000 miles) out of warranty and I discovered a problem. Is there anything I can do?
  94. 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?
  95. 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?
  96. My vehicle is using a lot of oil but there is no leak or smoke from the tail pipe.
  97. My vehicle over heated and I suspect the head gasket is blown, can this be tested?
  98. 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.
  99. My vehicle runs fine in normal driving. When accelerating heavily or trying to climb a hill it lacks power and will start to miss?
  100. 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?
  101. My vehicle runs very well but occasionally is hard to start. Could this be a dirty fuel filter?
  102. 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?
  103. My windshield washer pump has gone out twice in four years, any ideas?
  104. My windshield washers froze and damaged the pump. I thought washer fluid should keep this from happening.
  105. On hard acceleration my vehicle suffers from valve clatter, any ideas?
  106. Recently I replaced my windshield and the glass company said I should replace my wiper blades. I have never heard of this before.
  107. Should I carry full coverage insurance on my four-year old car or just liability?
  108. Should I expect better mileage or performance after replacing my timing belt?
  109. The battery was replaced in my Silverado and now the engine idles very low and almost dies when I turn on the AC.
  110. 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.
  111. The engine in my car looks dirty. Is it okay to pressure wash the engine?
  112. 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.
  113. 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?
  114. The headlights on my car have turned yellow with age. Can this be repaired without replacing the light assemblies?
  115. 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?
  116. The oil level in my vehicle rises about one quart per month, what could cause this?
  117. 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?
  118. 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.
  119. 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?
  120. 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?
  121. The serpentine belt on my vehicle keeps fraying and breaking.
  122. The shifter on my Ford Crown Vic wont move out of park.
  123. The speedometer on my Chevy Silverado reads very erratically? Sometimes it will read over 100 MPH when I am driving 30 MPH.
  124. The steering wheel in my vehicle shakes when stopped with the transmission in gear and the brakes on?
  125. 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.
  126. 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?
  127. There is a gauge on my dash that says RPM. What does this indicate?
  128. 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?
  129. 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?
  130. What are the symptoms of a bad fuel injector?
  131. What are the symptoms of a bad gas cap?
  132. What are the symptoms of a bad serpentine belt tensioner?
  133. What are the symptoms of a bad universal joint (U-joint) in a rear-wheel drive vehicle?
  134. What are the symptoms of a cracked cylinder head?
  135. What are the symptoms of a worn timing belt?
  136. What are the symptoms of broken motor mounts?
  137. What are the symptoms of leaking valve cover gaskets?
  138. What are the symptoms of needing an injector flush?
  139. What are the symptoms of needing spark plugs?
  140. What causes a fuel pump to fail?
  141. What could cause intake manifold on my 3.8L GM engine to have a small hole melted in it?
  142. What could cause no fuel pressure, when I can hear the fuel pump running?
  143. What could make my front wheel overheat and smoke?
  144. What do the letters after a vehicle model name mean?
  145. What does the term maintenance item mean?
  146. What does “full coverage” automobile insurance mean?
  147. What is a fuel injector?
  148. What is a MAP sensor?
  149. What is a mass air flow sensor?
  150. What is a timing belt?
  151. What is an interference engine?
  152. What is meant by the term bleed, in regard to automotive systems?
  153. What is the affect of driving a vehicle without the EGR system working?
  154. What is the best spark plug for my vehicle?
  155. What is the difference in an interference and non-interference engine?
  156. What is the freeze point of windshield washer fluid?
  157. What is the purpose of an EGR valve?
  158. What makes a catalytic converter fail?
  159. What percentage of antifreeze to water is necessary to maintain a -34 degrees Fahrenheit freeze point?
  160. What would cause a head gasket to start leaking again, shortly after replacement?
  161. What would cause a loud popping noise, coming from between my engine and transmission?
  162. What would cause a serpentine belt to smoke?
  163. When does a serpentine belt need to be replaced?
  164. When I accelerate my engine loses power and the check engine light comes on.
  165. 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?
  166. 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?
  167. When I turn on my air conditioner or defrost, my engine bogs down, like it is about to stall. What would cause this?
  168. When my battery was replaced the hold down broke. The shop said it was not important, what do you think?
  169. When my fuel tank is low there is a whining noise in the rear of my car?
  170. When replacing a timing belt, should I also replace the idler pulleys?
  171. Where can I find a list of interference and non-interference engines?
  172. Where is the idle control valve on my Chevy Silverado?
  173. Where is the rear main seal of an engine located?
  174. Which Ford engines use the two-piece spark plug that is prone to breakage?
  175. Why do catalytic converters get so hot?
  176. Why do diesel engines not need spark plugs?
  177. Why do estimates to replace my timing belt vary so greatly?
  178. Why do gaskets fail?
  179. Why does the speedometer go out on so many Chevy Silverado trucks?
  180. Why was I not notified there was a recall on my vehicle?
  181. Why would a dead battery cause my vehicle to fail State inspection?
  182. Why would my engine start leaking oil at several places, all at once?
  183. Why would my vehicle crank over but not start?
  184. Why would the serpentine belt on my car come off?
  185. Will a bad PCV valve cause my engine to develop sludge?
  186. Will changing to iridium spark plugs increase my fuel mileage?
  187. Will spark plugs with multiple electrodes increase fuel mileage and performance?
  188. With my engine off and the oil filler on my engine open, a lot of smoke comes out. What could be the problem?
ANSWERS
  1. 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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  2. 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?

    Tires contacting the road on vehicle in front of you when stopped
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  3. 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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  4. 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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  5. 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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  6. 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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  7. 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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  8. 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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  9. 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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  10. 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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  11. 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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  12. 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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  13. 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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  14. 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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  15. 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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  16. 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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  17. 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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  18. 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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  19. 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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  20. 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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  21. 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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  22. 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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  23. 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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  24. 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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  25. 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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  26. 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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  27. 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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  28. 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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  29. 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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  30. 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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  31. 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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  32. 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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  33. 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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  34. 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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  35. 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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  36. 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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  37. 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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  38. 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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  39. 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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  40. 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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  41. 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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  42. 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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  43. 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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  44. 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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  45. 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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  46. 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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  47. 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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  48. 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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  49. 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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  50. 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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  51. 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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  52. 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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  53. 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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  54. 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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  55. 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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  56. 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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  57. 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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  58. 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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  59. 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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  60. 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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  61. 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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  62. 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.

    Typical GM and Chrysler V-8 cylinder numbering Ford more often starts on the right (passenger) side and proceeds in numeric order on their V-8 engines.

    Typical Ford V-8 cylinder numbering 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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  63. 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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  64. 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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  65. 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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  66. 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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  67. 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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  68. 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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  69. 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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  70. 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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  71. 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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  72. 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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  73. 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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  74. 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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  75. 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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  76. 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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  77. 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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  78. 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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  79. 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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  80. 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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  81. 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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  82. 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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  83. 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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  84. 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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  85. 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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  86. 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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  87. 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.

    Timing belt teeth.

    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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  88. 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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  89. 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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  90. 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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  91. 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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  92. 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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  93. 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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  94. 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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  95. 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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  96. 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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  97. 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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  98. 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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  99. 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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  100. 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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  101. 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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  102. 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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  103. 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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  104. 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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  105. 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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  106. 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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  107. 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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  108. 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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  109. 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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  110. 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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  111. 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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  112. 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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  113. 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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  114. 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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  115. 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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  116. 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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  117. 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.

    Torx style opening in an automotive fastener
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  118. 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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  119. 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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  120. 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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  121. 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.

    Typical serpentine belt construction

    For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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  122. 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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  123. 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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  124. 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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  125. 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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  126. 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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  127. 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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  128. 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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  129. 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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  130. 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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  131. 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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  132. 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.

    Typical spring operated serpentine belt tensioner

    For more information on belts, see our Detailed Topics article, About Serpentine Belts.
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  133. 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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  134. 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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  135. 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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  136. 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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  137. 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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  138. 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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  139. 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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  140. 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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  141. 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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  142. 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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  143. 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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  144. 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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  145. 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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  146. 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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  147. 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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  148. 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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  149. 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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  150. 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.

    Typical timing belt with sprockets and idler pulleys
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  151. 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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  152. 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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  153. 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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  154. 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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  155. 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.

    An interference engine.

    See our Detailed Topic article All About Timing Belts for far more details.
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  156. 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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  157. 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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  158. 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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  159. 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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  160. 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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  161. 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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  162. 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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  163. 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.

    Small cracks in the ribs of a serpentine belt.

    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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  164. 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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  165. 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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  166. 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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  167. 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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  168. 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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  169. 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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  170. 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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  171. 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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  172. 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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  173. 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.

    Typical rear main seal.
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  174. 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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  175. 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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  176. 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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  177. 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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  178. 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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  179. 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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  180. 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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  181. 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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  182. 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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  183. 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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  184. 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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  185. 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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  186. 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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  187. 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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  188. 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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