Lifter / Lash Adjuster: Testing and Inspection

Failure of an hydraulic valve lash adjuster is generally caused by an inadequate oil supply or dirt. An air leak at the intake side of the oil pump or too much oil in the engine will cause air bubbles in the oil supply to the lash adjusters, causing them to collapse. This is a probable cause of trouble if several lash adjusters fail to function, but air in the oil is an unlikely cause of failure of a single unit.