RATTLE AND/OR BUZZ FORM I/P DURING BRAKE APPLY/RELEASE

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

MODELS/YEARS: 1990-91 SILHOUETTE AND 1988-92 CUTLASS SUPREME

This bulletin cancels and replaces Dealer Technical Bulletin 91-T-59 which should be discarded.

CONDITION:

---------- Some 1990-91 Silhouettes may exhibit a rattle or buzz type noise which seems to come from the instrument panel area in front of the driver. In addition, some 1988-91 Cutlass Supreme with J65 brakes and all 1992 Cutlass Supremes may exhibit a 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 Silhouettes built after vehicle number MT305086.

For Silhouettes built prior to this breakpoint, and for 1988-92 Cutlass Supremes, install a new vacuum check valve and rubber grommet kit, P/N 18018978, which is 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.