Camshaft, Lifters and Push Rods: Testing and Inspection

DESCRIPTION
Valve tappet noise may be caused by any of the following:
^ Excessive valve tappet gap.
^ Sticking valve tappet plunger.
^ Valve tappet check valve not functioning properly.
^ Air in lubrication system.
^ Leakdown rate too rapid.

Excessive Valve Tappet Gap may be caused by loose rocker arm bolts, excessive wear on valve tappet face, or worn rocker arms (6564), rocker arm seat or valve tip. With valve tappet (6500) collapsed, check gap between valve tip and rocker arm to determine if any other valve train parts are damaged, worn or out of adjustment.

A Sticking Valve Tappet Plunger may be caused by dirt, chips or varnish inside the valve tappet.

A Valve Tappet Check Valve that is not functioning may be caused by an obstruction such as dirt or chips that prevent it from closing when the camshaft lobe is lifting the valve tappet. It may also be caused by a broken check valve spring.

Air Bubbles in the lubrication system will prevent the valve tappet from supporting the valve spring load. This may be caused by incorrect oil level or by air being drawn into the system through a hole, crack or leaking gasket on the oil pump screen cover and tube (6622).