Gasket Replacement and Installation Gaskets are a means of sealing the mating surfaces between various components. Gaskets are used between the various parts of the engine to keep oil, coolant, air and fuel in their respective places. Rubber, cork or combination cork/rubber gaskets are often used to seal the oil pan, valve covers, water pump and timing chain cover. Metal gaskets are used between the cylinder head and engine block, and metal or asbestos gaskets are used to seal intake and exhaust manifolds. Over time, cork gaskets tend to become brittle and break. This allows oil to leak out of the engine. Tightening the cover bolts will sometimes stop a leak but usually the gasket must be replaced. Some late model engines use various chemical sealers (such as RTV silicone) in place of conventional gaskets. Either applying fresh sealer or substituting a conventional gasket can repair leaks.