Cylinder Sleeve
A metal liner inserted into a cylinder bore of an engine block to restore or create a durable cylinder wall.
A cylinder sleeve (also known as a cylinder liner) is a thin-walled metal tube pressed into the cylinder bores of an engine block to form the inner cylinder wall. Sleeves are typically made of durable cast iron or specialized alloys, providing a smooth, wear-resistant surface for the piston rings to slide against during combustion.
There are two main types of sleeves: dry sleeves, which fit tightly inside the block's existing cylinder bores and do not contact engine coolant directly; and wet sleeves, which make direct contact with the engine block's coolant jackets and rely on O-ring seals to prevent coolant from leaking into the crankcase.
Cylinder sleeves are commonly used in aluminum engine blocks, which are too soft to withstand piston friction, and in diesel engines to allow for easy rebuilds by replacing the sleeves instead of boring the block. They are also used to repair damaged cylinders that have suffered deep scoring or cracks, restoring the engine to standard specifications.