Lifter Noise Diagnosis

1. To determine source of lifter noise, crank the engine with cylinder head covers removed.
2. Feel each valve spring or rocker arm to detect noisy lifter. The noisy lifter will cause the affected spring and/or rocker arm to vibrate or feel rough in operation.
   NOTE:

   Worn valve guides or cocked springs are sometimes mistaken for noisy lifters. If such is the case, noise may be dampened by applying side thrust on the valve spring. If noise is not noticeably reduced, it can be assumed the noise is in the lifter. Inspect the rocker arm push rod sockets and push rod ends for wear.

3. Valve lifter noise ranges from light noise to a heavy click. A light noise is usually caused by excessive leak-down around the unit plunger or by the plunger partially sticking in the lifter body cylinder. The lifter should be replaced. A heavy click is caused by a lifter check valve not seating or by foreign particles wedged between the plunger and the lifter body. This will cause the plunger to stick in the down position. This heavy click will be accompanied by excessive clearance between the valve stem and rocker arm as the valve closes. In either case, lifter assembly should be removed for inspection and cleaning.
4. The valve train generates a noise very much like a light lifter noise during normal operation. Care must be taken to ensure that lifters are making the noise. If more than one lifter seems to be noisy, it's probably not the lifters.

Lifter Purge Guideline

1. Warm engine to standard idle conditions.
   NOTE:

   Engine noise may be in the form of a clicking, chatter, or clattering noise.

2. Listen to the engine for 30 to 60 seconds with the hood up and the engine cover removed.
3. If noise is present, de-aeration of the lifters is required.
4. Run the engine between 2000 and 3000 RPM for three to five minutes.
5. Return the engine to standard idle speed for 30 to 60 seconds.
6. Evaluate noise. If noise is present, repeat the run an additional 4 cycles.
   NOTE:

   The standard drive cycle will be about 10 - 15 miles of non- stop, combined highway and city driving.

7. If noise is present, take the vehicle on a standard drive cycle.
   NOTE:

   Use a feeler gauge to verify clearance is present between the lifter and cam base circle.

8. Evaluate the noise. If noise present, follow standard service procedure for lifter repairs or noise conditions.
9. Evaluate lifters for sponginess, check valve defects, and clearance.