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-VAN

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.

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:

Chevrolet MT119717 Pontiac MT210360 Oldsmobile MT305086

For vehicles built prior to these breakpoints, install a new vacuum check valve P/N 18018978.

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.