Noise

Hydraulic Lash Adjuster Noise may be caused by any of the following:
- Excessive collapsed hydraulic lash adjuster gap (valve clearance).
- Sticking hydraulic lash adjuster plunger.
- Hydraulic lash adjuster check valve not functioning properly.
- Air in lubrication system.
- Leakdown rate too rapid.
- Excessive valve guide clearance.
- Worn camshaft lobes.
- Worn roller follower.

An Excessive Collapsed Lash Adjuster Gap may be caused by wear of the lash adjuster face, roller follower or valve tip. With lash adjuster collapsed, check gap between camshaft lobe and roller follower to determine if any other valve train parts are damaged, worn or out of adjustment.

A Sticking Hydraulic Lash Adjuster Plunger may be caused by dirt, chips or varnish inside the hydraulic lash adjuster. The sticking can be corrected by disassembling the hydraulic lash adjuster and removing the debris causing the condition.

A Hydraulic Lash Adjuster Check Valve that is not functioning may be caused by an obstruction such as dirt or chips that prevent it from closing when the cam lobe is lifting the hydraulic lash adjuster. It may also be caused by a broken check valve spring.

Air Bubbles in the lubrication system will prevent the hydraulic lash adjusters from supporting the valve spring load and may be caused by too high or low of an oil level in the oil pan (6675). Air bubbles may also be caused by air being drawn into the system through a hole, crack or leaking O-ring on the oil pump screen cover and tube (6622).

If The Leakdown Time is below the specified time for used hydraulic lash adjusters, noisy operation may result. If no other cause for noisy hydraulic lash adjusters can be found, the leakdown rate should be checked and any hydraulic lash adjusters outside the specification should be replaced.