You may have heard the expression “blown a gasket” before – but what are gaskets?

When two pieces of metal are bolted together, the microscopic differences between the two surfaces prevent them from pressing together absolutely flat. These gaps happen no matter how precisely the metal is machined, and can change as the metal heats up and cools. When you’re trying to keep hot gasses trapped in a cylinder or engine coolant or oil from leaking out of the engine, it’s important that the gaps be filled in.

Gaskets are thin sheets of flexible materials that are used to fill in these gaps. They allow metal parts to be bolted together without leaking the fluids that are transferred between the two. Gaskets are commonly made from brass, steel, rubber, and even paper compounds. In addition to proving more conductive passages for fluids to flow, they also serve as insulation to isolate some parts from shock or vibrations that could cause leaks, and create tighter fitting parts that are more likely to stay in place.