Deactivating Hydraulic Lash Adjuster

When fixing an engine, the hardest part is to get the hydraulic lash adjusters (HLAs) deactivated. This is important during repair work to diagnose valve train noise or wear. Hydraulic lash adjusters have pre-set clearance between the camshaft and valves while providing automatic adjustment with oil pressure. When deactivated, the hydraulic compensator is removed, allowing inspection of mechanical clearances and detection of faulty components. The deactivation process may be used to identify other wear, like weak springs, cam lobes, or sticking hydraulic valves. Deactivation will generally be done during testing and not while in normal operation, since HLAs are designed to operate around the clock to make hydraulic adjustments to lash. Proper deactivation of the HLA allows reliable resets in valve adjustment that improve engine performance overall.