Valve stem seals are used in internal combustion engines to seal between the valve stem and the valve guide. They are typically located at the top of the valve stem, where the valve stem passes through the cylinder head.
The primary function of valve stem seals is to control the lubrication of the valve stem and prevent oil leakage into the combustion chamber. They play a vital role in maintaining proper engine performance, reducing oil consumption, and preventing issues such as oil burning, excessive oil consumption, and fouled spark plugs. Materials such as rubber, silicone, or other elastomers can withstand the high temperatures and pressures within the engine. They are designed to fit tightly around the valve stem and create a barrier preventing oil from entering the combustion chamber while allowing a thin oil film for lubrication.