A cylinder liner is a cylindrical part to be fitted into an engine block to form a cylinder. It is one of the most important functional parts to make up the interior of an engine.
This is called Cylinder liner in Japan, but some countries(or companies) call this Cylinder sleeve.These are main functions of Cylinder Liners.
Cylinder liners are of the shape of hollow cylinders fitted on the inner surface of a I. c. engine cylinder. Purpose of using liners is once worn out change of liners will serve the need. Otherwise the entire engine block is to be changed which is not economical.
Secondly the inner surface of the liners comes in contact with the reciprocating piston. So the coefficient of friction at that surface should be low and that low coefficient of friction should be maintained at elevated temperature.For this reason liners are made of special alloys (cadmium alloy).The material; engine block is made of which can not serve the purpose.