Gasket

A gasket is a thin seal clamped between two mating surfaces, such as the cylinder and head, crankcase halves or a side cover. It fills tiny irregularities in the metal so that oil, coolant, fuel or combustion gases cannot escape.

Gaskets are made of paper, fibre, rubber, composite materials or multi-layer steel depending on the temperature and pressure they face. Many are designed to be used only once, because they compress and take a set when tightened.

When a cover is removed, fit a new gasket, clean both surfaces carefully without scratching them and tighten the bolts evenly to the specified torque. Weeping oil around a joint is usually the first sign that a gasket is failing.