DIAGNOSE – ENGINE LOSING COOLANT

By Carl O’Reilly

SYMPTOM SUMMARY
The engine loses coolant. This may be in the form of a leak or an internal malfunction that causes the coolant to be consumed in the combustion process. If the engine is exhibiting an overheating condition and there is no leak present, refer to the “Engine Overheating” symptom on this website.

USUAL CAUSE
Coolant loss is usually the result of a coolant leak. A blown head gasket or cracked cylinder head can also cause the coolant to be consumed. In this case, no leak will be present but the coolant level will continually go low.

DIAGNOSIS
Check and fill the coolant level as necessary while the engine is cold. Start the engine and allow the engine to reach operating temperature. Shut the engine off. The cooling system should be under pressure at this point and any leaks should be easily detectable. Inspect the hoses and the fittings for leaks or loose clamps. Inspect the water pump and thermostat housing for leaks. Inspect the radiator tanks and cooling tubes for signs of leakage.

PRECAUTIONS, TIPS, and NOTES
The cooling system is under pressure when the engine is hot. Use caution not to open the system when it is hot. Hot coolant can rapidly discharge from the opening causing severe burns. A cooling system pressure tester can be rented from some auto parts stores. This system allows you to pressurize the cooling system so that it can be inspected for leaks. This can be an aid when trying to locate small or intermittent leaks.