How Does Oil Get Past a Head Gasket Into Water?

Head Gasket

Head gaskets separate the flows of oil and coolant between the engine block and the cylinder head. When the head gasket warps due to an overheated engine, then the fluids can leak into each other or into other components of the combustion chamber. This can cause extensive damage, not only to the oil and coolant chambers, but to all parts of the engine.

Damage

Most cars utilize aluminum head gaskets, which are lighter and softer than the aftermarket option of iron head gaskets and so are more likely to expand if the engine overheats. Even the addition of a non-stick coating to the surface of the aluminum head gasket is sometimes not enough to protect it from warping. This can cause leaks of not only the oil, but also the coolant and combustion gases. This results in oil or coolant burning out through the exhaust and causing intense pressure in the cooling system. Coolant leaking onto the cylinders results not only in damage to the catalytic converters, but causes hydrolock. This is an immobilization of the engine due to damaged pistons and consequently a damaged connecting rod and cylinder block. The least immediate damage to expect in the event of a blown head gasket is an abnormal expulsion of steam or white smoke from the tailpipe while the car continues to drive without a problem. However, loss of coolant and engine overheat are inevitable given the damage to the head gasket and the resulting combination of gases and fluids in parts of the engine.

Diagnosis

Diagnosing a blown head gasket can include a chemical test on the radiator to determine whether combustion gases are present in the coolant. The spark plugs could also be removed to determine if water sprays through the holes while the engine runs. Replacing a head gasket is a complex and sometimes dangerous procedure that should only be done by professionals since it involves disassembling the engine to check for additional damage caused by fluid leaking into other components. While replacement heads range in price up to around $100, tests and repairs can take several hours and cost over $1,000 considering the amount of labor involved.