Lifter / Lash Adjuster: Description and Operation

Description
The valve gear incorporates hydraulic tappets which keep the valve clearance within a limited working range of 2.05 mm (0.081 inch), which is between 18.75 and 20.8 mm (0.738 - 0.819 inch) from the cam to the valve. Each tappet has two storage chambers and one high-pressure chamber, which is sealed against one of the storage chambers by means of a spring-loaded ball valve. A return spring in the high-pressure chamber acts on the sliding plunger so that any clearance between the tappet and the base circle of the cam is eliminated. At the same time, the highpressure chamber expands and makes up the oil volume to compensate for leakage losses in the gap between the plunger and cylinder which occur at actuating pressure. Under some conditions the hydraulic tappets may give rise to a chattering noise of varying intensity. In most cases this noise will be short-lived and no remedial action will be necessary. Details are given in the following of the most common types of noise, the most probable cause of the noise and preliminary action which may be taken to eliminate the noise.