Hydraulic Lifter(S) Noise Diagnosis

Proper noise diagnosis is essential in locating the source of an Noise, Vibration, and Harshness (NVH) complaint. Locating a lash adjuster (tappet) type noise can sometimes be difficult. As a result, an initial misdiagnosis may occur.

Refer to the following chart for possible causes and correction of a lash adjuster (tappet) type noise.

LASH ADJUSTER (TAPPET) NOISE CHART

POSSIBLE CAUSES	CORRECTION
1. Engine oil level-too high or too low. This may allow aerated oil to enter the adjusters and cause them to be spongy.	1. Check and correct the engine oil level.
2. Insufficient running time after rebuilding a cylinder head. De-aeration of the lash adjusters may be required	2. See Below: (a) Run the engine between 2000 and 3000 RPM for three to five minutes. Return the engine to standard idle speed for 30 to 60 seconds. Evaluate noise. If noise is present, repeat the process an additional 4 cycles. If noise is present after additional cycles, take the vehicle on a typical drive cycle. NOTE: The typical drive cycle will be about 10-15 miles of combined highway and city driving. Avoid marshaling maneuvers (quick start/stop operation) during evaluation. (b) Low speed running of up to 1 hour may be required to fully evacuate trapped air from the valvetrain system. During this time, turn engine off and let set for a few minutes before restarting. Repeat this several times after engine has reached normal operating temperature.
3. Debris/air trapped in the intake/exhaust lash adjuster(s).	3. Intake adjuster only: Check the intake lash adjuster(s) for a collapsed condition while installed in the cylinder head. Press down on the intake rocker arm in a manner that would compress the intake lash adjuster(s). Normal intake adjuster(s) should feel very firm and difficult to compress. If the intake lash adjuster(s) can be compressed or there is lash between the rocker arm and cam lobe, remove the suspect intake lash adjuster(s) from the cylinder head for further evaluation. Refer to LIFTER(S), HYDRAULIC, REMOVAL AND INSTALLATION . (a) A collapsed lash adjuster(s) will remain in a compressed state with no external force and no return force from the spring. This is caused when debris jams the piston causing the top plunger of the lash adjuster to stay collapsed in the bottom housing. If the lash adjuster(s) are confirmed to be collapsed, replace the lash adjuster(s). (b) A spongy lash adjuster(s) will return to its original state after being compressed. This is caused by air trapped in the lash adjuster(s) or debris blocking the check ball. The lash adjuster(s) will compress under a force and be returned to the original position under a spring force. If the lash adjuster(s) are confirmed to be spongy, repeat Step 2 as further run time may be required to de-aerate the lash adjuster(s). After repeating Step 2, see Steps 1, 4, 5, and 8. Exhaust lash adjuster(s) only: Check the exhaust lash adjuster(s) for a collapsed condition while installed in the cylinder head. Press down on the exhaust rocker arm in a manner that would compress the exhaust lash adjuster(s). Normal exhaust adjuster(s) are designed to be compressible, but they will exert a reactionary spring force during compression and return to full expansion without a compression force. If the exhaust lash adjuster(s) can be compressed without returning to full expansion, remove the suspect lash adjuster(s) from the cylinder head for further evaluation. Refer to LIFTER(S), HYDRAULIC, REMOVAL AND INSTALLATION . (c) A collapsed lash adjuster(s) will remain in a compressed state with no external force and no return force from the spring. This is caused when debris jams the piston causing the top plunger of the lash adjuster to stay collapsed in the bottom housing. If the lash adjuster(s) are confirmed to be collapsed, replace the lash adjuster(s).
4. Low oil pressure.	4. See below: (a) Check and correct the engine oil level. (b) Check the engine oil pressure. Refer to LUBRICATION, DIAGNOSIS AND TESTING . (c) Check for excessive main bearing clearance and correct. Refer to BEARING(S), CRANKSHAFT, MAIN, STANDARD PROCEDURE . (d) Check for a worn oil pump. Refer to PUMP, ENGINE OIL, INSPECTION . Check the camshaft journals and the bearing bores for abnormal wear patterns, scoring, grooving, fatigue, pitting or a foreign material. Refer to CAMSHAFT, ENGINE, REMOVAL AND INSTALLATION .
5. A plugged oil restrictor in the oil passages to the cylinder head(s).	5. Check the cylinder head oil passages for blockage. Clean or replace as necessary.
6. Worn valve guide(s).	6. Measure the valve stem-to-guide clearance. Refer to VALVES, INTAKE AND EXHAUST, INSPECTION .
7. Rocker arm loose, adjuster stuck or at maximum extension and still leaves lash in the system.	7. See below: (a) Check the camshaft journal and lobe for abnormal wear patterns, scoring, grooving, fatigue, pitting or a foreign material. Refer to CAMSHAFT, ENGINE, REMOVAL AND INSTALLATION . (b) Check the rocker arm(s) for proper alignment to the camshaft lobe(s) and valve stem(s). Refer to ROCKER ARM, VALVE, REMOVAL AND INSTALLATION . (c) Check the lash adjuster(s) for proper operation and replace as necessary. Refer to LIFTER(S), HYDRAULIC, REMOVAL AND INSTALLATION .
8. Air ingested into the engine oil due to a broken or cracked oil pump pickup tube.	8. Check the pickup tube and replace as necessary. Refer to PICK-UP, OIL PUMP, REMOVAL AND INSTALLATION .