For 1990-2009 cars

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

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

#### MODELS/YEARS: 1991 NINETY EIGHT AND TORONADO WITH 3800 ENGINE (VIN CODE L)

A hum or whine noise between 1200 and 1600 RPM on the above model cars can sometimes be corrected by installing a 1992 style engine front (timing) 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 to approximately 4000. 4. Gradually lower RPM to approximately 1500 and listen for hum/whine noise. 5. If noise is present, install engine front cover (P/N 12353384). Follow the service procedure outlined in the appropriate service manual.

Parts are currently available from GMSPO.

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.