SNAPPING NOISE IN THE ENGINE COMPARTMENT (NEW P/N RELEASED)

Subject: SNAPPING NOISE IN THE ENGINE COMPARTMENT NEAR FRONT OF ENGINE (REPLACE CRANKSHAFT PULLEY)

Models Affected: 1987-92 GRAND AM AND GRAND PRIX MODELS

ENGINE APPLICATIONS: Quad-4 and Quad OHC (VINs A, D, and 3) (RPOs LGO, LD2, L40)

CONDITION:

A snapping noise in the engine compartment near the front of the engine.

CAUSE:

A static electric charge may be built up in the crankshaft pulley outer ring by serpentine belt friction. If the charge builds to a high enough level, it discharges by arcing to the engine front cover. A snapping sound, similar to a spark plug wire arcing to ground, is created. This static build up is more likely in low humidity conditions and with a serpentine belt which has been in use. The arcing may not be apparent at all in higher humidity conditions and is less likely with a new belt.

CORRECTION:

Replace crankshaft pulley with updated grounded outer ring crankshaft pulley. Refer to Parts Information for correct crankshaft pulley part number.

SERVICE INFORMATION:

Verify the crankshaft pulley is discharging to front cover. Discharge can be seen when engine compartment is relatively dark. DO NOT replace serpentine belt to correct this condition; replacing the belt will only eliminate the condition temporarily. Refer to Section 6A7 of the service manual for crankshaft pulley replacement procedure.

PARTS INFORMATION:

Vehicles built after February 1992 will have the updated crankshaft pulley. Refer to date on the label on the end of the driver side door.

New Pulley Part Number Diameter Application ----------- -------- ----------- 24573264 Small 1989-91 (VIN A) 1992 Quad 4 (VIN A - W41)

24573015 Large 1987-91 (VIN D) All 1992 (VIN A - except W41, D, and 3)

Parts are currently available from GMSPO.

WARRANTY INFORMATION:

Labor Time Operation Number: J0700

Labor Time Allowance: Refer to current Labor Time Guide for labor time allowance.

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.