The head gasket sits between the engine block and cylinder head in an internal combustion engine. Its purpose is to seal the cylinders to ensure maximum compression.

Occasionally, the compression in the cylinder may cause a leak to form in the gasket (a "blown" head gasket). This problem has been exacerbated by the use of aluminum rather than iron cylinder heads; while lighter than iron, aluminum has a much greater thermal expansion rate, which in turn causes a great deal more stress to be placed on the head gasket. Engine makers have responded to this by adding a non-stick coating such as Teflon to the surface of the head gasket.

If the gasket blows, a variety of problems can occur, from compression loss (leading to power reduction, or a rough engine), to exhaust gasses being forced into the cooling system, leading to the engine overheating and increased engine wear due to the motor oil being mixed by antifreeze (coolant). If a very large amount of coolant leaks into the cylinders, hydrolock can occur, causing extensive engine damage.

Zylinderkopfdichtung | Joint de culasse (moteur) | Koppakking