ENGINE KNOCKING NOISE NEW SPRING & BEARING ASSEMBLY
NEW DESIGN SPRING AND BEARING ASSEMBLY (CAMSHAFT THRUST) (Revised to change Part Number and add Art)
VEHICLES AFFECTED: 3.0L 82-85 LK9 (VIN CODE E); 85-87 LN7 (VIN ------------------ CODE L) V6 ENGINE; AND 3.8L 84-85 LN3 (VIN CODE 3); 86 LG2 (VIN CODE B); 86-87 LG3 (VIN CODE 3) V6 ENGINE
Some of the above engines may experience excessive wear to the front cover thrust surface and the camshaft thrust button. An engine with this condition may exhibit a knocking noise most audible just above idle. This knocking noise could be caused by the camshaft chucking (fore and aft movement) in this block. (Refer to Figures).
A needle bearing and spring assembly is available as a service part, Part Number 25532588, to repair the above conditions. The needle bearing will reduce wear to the front cover thrust surface, and the spring has a higher load rating, which will reduce camshaft chucking.
NOTICE: A higher load rate spring SHOULD NOT be used with the early design Phenolic plastic button.
When servicing these engines with the front cover removed for any other reason, install the new spring and bearing if wear to the button is noted. The front cover should also be replaced if excessive wear to the thrust surface exists.
Replacement of the camshaft is not necessary unless other obvious conditions are visibly detected.
Use applicable labour operation number and time.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
