TUBE AS 9G9758 - Caterpillar

Caterpillar EnginesValve lash adjustment is a normal part of engine maintenance and should not be claimed as a warranty item. If the valve train must be removed or disturbed to do warranty work on other engine components, then valve lash adjustment can also be listed on the claim.
The rate of valve train component wear does not stay the same throughout the life of the engine. Valve train wear is greatest during the first few hours of operation. After this, the components wear only a small amount and valve lash needs only minor periodic adjustment.
Valve lash measurements made on the engine are sometimes greater than the plus/minus specifications. This is not necessarily an indication of defective material or workmanship. It does not mean that a failure of the valve train will happen soon.
The specified valve lash setting simply allows the valve train components to have a satisfactory service life. Always make valve lash adjustments when the engine is completely cool.