What is a head gasket?

There is a gasket between the cylinder block and the cylinder head. This gasket plays a vital role, not only to prevent the seepage of oil, but also of coolant and combustion gases, the latter of which is at very high temperature and pressure.

If the gasket fails, then oil, coolant or combustion gases may be able to escape, with potential dire consequences to the engine:

  • loss of compression in one or more cylinders, causing a misfire and loss of power.
  • loss of coolant, and subsequently overheating of the engine which, with an alloy design , will cause extensive damage and warping of the head and other castings.
  • loss of oil lubrication, with potential damage to the reciprocating and rotating internal components of the engine.
  • Mixing of oil and coolant, causing the oil to emulsify. The ensuing sludge does not circulate well, and causes overheating.

If, for any reason a head gasket failure is suspected, immediately switch off the engine and seek expect advice from HEAD TECH.

A head gasket failure  is said to occur when there is a breech of the gasket, allowing the escape and potentially mixing of water, oil and combustion gases. The picture to the right shows an engine being stripped down following a gasket failure. In the oil galleries, instead of normal brown honey-coloured oil, there is brown emulsion everywhere, signifying a failure of the gasket between the oil and coolant passage ways. This engine will need its oilways and cooling system throughly flushed out before reassembly.