RATTLE/BUZZ NOISE FROM I/P DURING BRAKE APPLY/RELEASE

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

Models Affected: 1990-91 TRANS SPORT 1988-92 GRAND PRIX MODELS ----------------------------------------------------------------------------

This bulletin has been revised to clarify the application and add the Grand Prix model. This bulletin cancels and replaces bulletin 91-5-6 issued 2/91. Please discard bulletin 91-5-6.

Condition:

---------- Some 1990-91 Trans Sport models 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 Grand Prix models with J65 brakes and all 1992 Grand Prix models 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 breakpoint MT210360 for the 1990-91 Trans Sport.

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

Parts are currently available from GMSPO.

TRANS SPORT GRAND PRIX

Labor Operation Number: H1240 T1812

Labor 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.