During some point in their service lives, most older gasoline engines built with cast-iron cylinder blocks and aluminum cylinder heads will need a cylinder head gasket replacement. The vulnerability of aluminum-head engines to head gasket failure is caused by the aluminum cylinder head expanding approximately 1.5 times more than the cast-iron block. Although measured in thousandths of an inch, this small and seemingly insignificant difference between the expansion rates of aluminum and cast iron will eventually wear out the head gasket and cause failure.

Head gasket failure is also aggravated by design factors such as deficiencies in the number and placement of cylinder head bolts, the thickness of the cylinder head and cylinder block deck surfaces, and the addition of supercharging or turbocharging on the engine.

Last, neglected cooling system maintenance, and spark timing and exhaust valve gas recirculation (EGR) errors in the electronic engine management system, may cause cylinder detonation, which eventually destroys the metal head gasket "fire ring" sealing the cylinder from the cooling system itself. Since head gasket failures are relatively common, a head gasket replacement offers numerous opportunities to sell new cylinder heads, machine shop services and complete engine assemblies as well as the belts, hoses, and cooling, ignition, fuel system and other related parts. In fact, cylinder head gasket failure may...