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OPERATION The rocker arm is the pivot point between the cam- shaft lobe and the valve. DIAGNOSIS AND TESTING LASH ADJUSTER (TAPPET) NOISE DIAGNOSIS Proper noise diagnosis is essential in locating the source of a NVH complaint. Locating a lash adjuster (tappet) type noise can sometimes be difficult. As a Refer to the following chart indicating possible lash adjuster (tappet) noise sources and possible sources Refer to Lash Adjuster (Tappet) Noise Chart for Possible Causes and Correction of a lash adjuster POSSIBLE NOISE SOURCES POSSIBLE NOISE MISDIAGNOSIS SOURCES Spongy/soft/aerated lash adjusters. Exhaust leak. Missing lash adjuster swivel contact pads. Exhaust rocker arm-to-cylinder head cover contact. Intake rocker-to-camshaft bearing journal contact. Piston pin bore fit. Rocker arm bind-up. Timing drive hydraulic tensioner tick. Intake rocker arm-to-spark plug tube contact. Accessory drive belt deterioration. Excessive cam end play. Piston-to-bore clearance knock. Broken valve spring. Crankshaft bearing noise. Broken/loose camshaft sprocket bolt. Incomplete cam lobe machining. Cracked lash adjuster cartridge body. LASH ADJUSTER (TAPPET) NOISE CHART POSSIBLE CAUSES CORRECTION 1. Engine oil level—too high or too low. This may cause 1. Check and correct engine oil level. 2. Insufficient running time after rebuilding cylinder 2. Low speed running of up to 1 hour may be required 3. Air trapped in lash adjuster (after 1 hour run time). 3. See below: (a) Check lash adjusters for sponginess while installed (b) Before proceeding, perform Lash Adjuster Bleeding (c) If lash adjuster(s) are still spongy, replace with new CS ENGINE 3.5L 9 - 47 ROCKER ARM SHAFT/ ROCKER ARM / LASH ADJUSTER (Continued) |