HUM/WHINE NOISE FROM FRONT OF ENGINE-INSTALL NEW FRT. COVER

SUBJECT: HUM/WHINE NOISE FROM FRONT OF ENGINE (INSTALL NEW ENGINE FRONT COVER)

VEHICLES AFFECTED: 1990-91 TPI/3800 SUPERCHARGED V6

A hum or whine noise between 1200 and 1600 RPM's on the above model cars can sometimes be corrected by installing a 1992 style engine front cover. Some vehicles were built with front covers that may exhibit a harmonic resonance between the oil pump and cover.

DIAGNOSIS:

----------- 1. Engine at normal operating temperature 2. Sitting in vehicle with windows closed 3. Raise engine RPM's to approximately 4000 4. Gradually lower RPM's to approximately 1500 and listen for hum/whine noise 5. If noise is present, install engine front cover, part number 12353384. Follow the service procedure outlined in the appropriate service manual.

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.