RATTLE/BUZZ FROM THE I/P AREA INSPECT VACUUM CHECK VALVE

SUBJECT: RATTLE/BUZZ FROM INSTRUMENT PANEL DURING BRAKE APPLY/RELEASE (INSTALL NEW VACUUM CHECK VALVE)

VEHICLES AFFECTED: 1990-91 U-VANS, 1988-92 "W"

Condition:

---------- Some 1990-91 U-vans may experience a rattle or buzz type noise which seems to come from the instrument panel area in front of the driver.

In addition, some 1988-1991 "W" cars with J65 brakes and all 1992 "W" cars may experience rattle or buzz type noise which seems to come from the instrument panel area in front of the driver.

Cause:

------- A vibration in the vacuum check valve on the power brake booster.

Correction:

----------- To eliminate this noise, a revised vacuum check valve has been released. This new check valve is on all vehicles built after VIN breakpoints indicated below for the 1990-91 U-vans.

Chevrolet MT119717 Pontiac MT210360 Oldsmobile MT305086

For vehicles built prior to these breakpoints, and for 1988-92 "W" cars install a new vacuum check valve and rubber grommet kit, P/N 18018978.

Parts are currently available from CANSPO.

U-Van W-Car ----- ----- Labour Time: 0.2 Hour 0.2 Hour

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.