In automobile engines, the cylinder heads are sealed to the engine block with cylinder head gaskets. These gaskets serve to seal the combustion chambers and passageways in the engine that transfer fluids from one part of the engine to another. Problems don't often arise with head gaskets. However, when a cylinder head gasket does fail, knowing some of the symptoms of a head gasket problem can help you diagnose it.
When a head gasket develops a leak between the cylinder and a water jacket in the block, coolant leaks past the gasket and into the combustion chamber. Coolant is then heated by the combustion process and exits through the exhaust system as steam. This appears as white smoke coming from the exhaust pipe. How thick this smoke is depends on the severity of the leak.
Head gaskets that are leaking around the water jacket, cylinder and oil passage allow coolant to escape past the gasket and into the oil passage. Coolant mixes with the oil and creates a whitish to dark brown sludge in the oil. This can usually be found by looking inside the oil filler cap, on the dipstick and by draining the oil.
A bad head gasket can cause a drop in the coolant level and changes in cylinder compression, and let combustion gases from one cylinder leak over into an adjacent cylinder. These problems interfere with the engine's ability to dissipate heat and result in higher operating temperatures and overheating.
A leaking head gasket can allow oil or coolant to enter the combustion chamber, which can foul the spark plug and result in poor ignition of the fuel mixture. A blown head gasket also can allow gases to escape from the cylinder, reducing the total cylinder pressure and the power produced by that cylinder. In all of these cases, the result is rough running and degraded performance.