ENGINE NOISE TICKING EXCESSIVE ROD SIDE CLEARANCE

MODELS: CABALLEROS WITH 3.8L ENGINES (RPO L05 VIN CODE "A")

A light ticking noise similar to overhead noise may be heard coming from the lower part of the engine. This noise is most pronounced at the rear of the front wheel opening. The noise occurs when the engine speed is slightly above idle and the vehicle is in gear or under a light load. The level of the noise will generally decrease if the EST harness is unhooked at the distributor. The noise will generally disappear when the spark plug wire on the cylinder is shorted to ground.

The noise may be caused by excessive side clearance between the connecting rod and the crankshaft journal thrust surfaces on the number one, three or five cylinder. The clearance should be checked using a dial indicator or feeler gauge. If a feeler gauge is used, the gauge should be placed next to the thrust surface on the counterweight and not next to the thin will section between two adjacent rods. Take care to assure the feeler gauge is fully seated on the journal and not on top of the narrow raised thrust surface. See Figure No. 1 for clarification. Clearance measurements should be made at several places around the journal.

If the rod clearance exceeds 0.015 inches on the Number 1, 3 or 5 cylinder, the rod should be replaced. A new rod is available which is 0.010 in. thicker than the original. The part number of this rod is 25516444. The new rod will reduce the clearance to the low side of the published limits.

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.