Cylinder Liner

The cylinder liner of an engine is is inserted into the cylinder jacket or cylinder block and in which the piston slides. The piston and cylinder liner are normally paired in terms of materials and parts.

They are cast or pressed into the block to give the required different characteristics to the block metal.

The functions of a Cylinder Liner are:

1. Strength to resist the gas pressure
2. Provide a bearing surface to the piston and piston rings
3. Maintain strength and functions at high temperatures
4. Resist corrosion
5. Symmetrical in shape
6. No distortion of inner surface due to restraining fixings

There are basically two types of cylinder liner:

1. Dry Liner – block has closed coolant channels and liner interfaces with block casing
   • Advantages of Dry Liner:
     • simpler to replace
     • no danger of water leakage either in to crankcase or the combustion chamber
     • due to absence of heavy flanges at the top of the liner, cylinder centres can be reduced
     • better cooling of upper part of the liner
   • Disadvantages of Dry Liner:
     • Complicated cylinder block casting
     • Decreased heat flow through the composite wall
2. Wet liner – outer surface provides seal to coolant channels and is directly cooled by coolant.
   • Advantages of Wet Liner:
     • Easier block casting as the large internal cores of the cylinder block can be properly supported
     • cylinder block is relieved of the stresses due to longitudinal expansion of the liner
   • Disadvantages of Wet Liner:
     • Difficult to replace
     • Danger of water leakage in to the crankcase and the combustion space if the casting is defective.

Scoring

A severe form of wear characterized by the formation of extensive grooves and scratches in the direction of sliding.

Varnish

A hard, dry, generally lustrous deposit that can be removed by solvents but not by wiping with a cloth.