When the coolant level drops, there is a leak in the system
There are many places that cooling systems may leak, some obvious and others difficult to locate. Accurate diagnosis and repair will keep the problem from expanding drastically.
Many times coolant will NOT be seen dripping or no leak will be visible. This is often the case with a leaking water pump. The air from the fan may blow the coolant against the hot engine block where it is evaporated.
Small leaks in a radiator core will rarely drip. The coolant runs down the hot surface of the radiator. The air from the fans and the heat of the radiator quickly evaporate the coolant. Other sources of leakage, that may not be seen include intake manifold gaskets and cracked cylinder heads.
Paying for a professional diagnosis is by far less expensive than allowing a cooling system to leak. Professionals use pressure testers, fluorescent dye and other methods to find leaks that do not show up otherwise.
Adding water to a leaking system will very quickly cause the problem to get much worse. When the level drops, there is already a problem. Many times the coolant has become acidic and is attacking the system. Adding water further dilutes corrosion protection and introduces chemicals into the system. Tap water may contain minerals, fluoride and chlorine which can affect the cooling system.
Coolant should always be premixed, 50/50 with distilled water before adding to the system. Many manufacturers are now producing pre-mixed coolant. This is best for toping off, until the system can be repaired, but does not address air which may be entering the system through the leak. Oxygen in air will drastically increase the rate of corrosion in the system.
Aluminum radiator cores often start to leak at the connection to the tanks. Leakage in this area is an outward sign of internal corrosion. Such a radiator is non-repairable and should be replaced. Trying to flush corrosion out of a radiator, is a waste of time and may cause damage to other components. A radiator in this condition also indicates other problems may be present. Such a system should be tested and monitored closely to prevent future problems.
Another common failure is a crack in the plastic tank. This will almost always be on the inlet tank, as it runs much hotter than the outlet tank. Heat and time combine, plastic becomes brittle and breaks. There is no repair for a broken tank that will last. Replacement of the radiator and coolant are by far the least expensive and best repair. Proper repair may prevent thousands in collateral damage if caught early. Once the engine starts to overheat, other damage will be done and cost with escalate drastically.
Cracks can also result from a system that is over-pressure. This is one symptom of a blown head gasket. Replacement of the radiator, without correcting the problem will normally result in other components blowing out and possible repeat radiator failure.
If properly conducted, a carbon dioxide test will often show combustion leaking into the coolant. A carbon dioxide test is a wise precaution if the engine has been overheated or shows any outward signs of problems.
This tank has been damaged by steam. Steam is many times hotter than a radiator tank can tolerate. The edges of the hole show signs of the plastic melting.
Often such damage is the result of a warped or cracked cylinder head or blown head gasket. Combustion entering the coolant will produce steam that can melt radiators, intake manifolds and more. Such damage calls for a much higher level of diagnosis and repair.
Improper service and not bleeding air from the cooling system can result in hot spots that produce steam. Removing the thermostat may cause coolant to circulate at too high a velocity This erode the tubes on a radiator or heater core. Increased flow also means the coolant does not remain as long in the radiator and may not give off the heat needed to cool the engine. The engine thermostat should never be removed or substituted with a lower temperature than specified.
Cooling system problems are easy to prevent but very difficult to solve. Corrosion cannot be flushed out of a radiator. Coolant should be tested and replaced when the pH approaches seven. Discoloration is another symptom of a problem. Any coolant that is dark, rusty in appearance or smells of ammonia should be replaced and the system retested every six months.
Cooling system diagnosis
Overheating that occurs when sitting still and gets better when the vehicle starts to drive is normally an air flow issue. Cooling fans must move air through the radiator or it will overheat. Make certain all fans are working, at the proper speed.
Overheating that occurs when driving at speed is a capacity issue. This is a symptom of a stuck thermostat, lack of coolant flow, plugged radiator or blown head gasket, cracked or warped cylinder head. The cost of a proper diagnosis and repair are nothing compared to the damage that will result from overheating.
For additional information, please also see part one of this article