Interior - Metallic Buzz/Rattle From I/P, Brakes Applied

File In Section: 5 - Brakes

Bulletin No.: 73-50-19

Date: May, 1997

Subject:
Metallic Buzz/Rattle Noise from Instrument Panel Area with Brake Pedal Depressed (Install a Revised Check Valve)

Models:
1995-97 Buick LeSabre, Park Avenue, Riviera
1995-97 Cadillac Concours, DeVille, Eldorado, Seville
1995-96 Oldsmobile Ninety Eight
1995-97 Oldsmobile Aurora, Eighty Eight
1996-97 Oldsmobile LSS
1997 Oldsmobile Regency
1995-97 Pontiac Bonneville

Condition

Some owners may comment on a metallic buzz or rattle type noise when the brake pedal is depressed. This noise may seem to come from the instrument panel cluster area and has been described as sounding like an ABS system self-test or speedometer cable type sound. Brake pedal force and engine load may affect the ability to reproduce the sound.

Cause

The cause of this noise may be the brake booster vacuum check valve resonating in response to engine vacuum pulsations.

Correction

A revised check valve, P/N 18029764, is available to correct this condition.

Diagnose and repair brake booster check valve noise as follows:

1. Determine the brake pedal force and engine throttle load needed to reproduce the noise. Also, determine if the transmission must be in drive range instead of park position.

Important:
There is no power brake assist available when the vacuum check valve is separated from the brake booster.

2. Remove the brake booster check valve and seal the valve with tape to prevent a vacuum leak.

3. If the noise can only be reproduced in drive range, then block the wheels to prevent vehicle movement.

4. Attempt to reproduce the booster check valve noise. If the noise is gone, replace the check valve with revised P/N 18029764. If the noise persists, then check for other conditions that can cause the noise such as grounded out powertrain components.

Parts Information

Parts are currently available from GMSPO.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation Labor Time

Use published labor
H1240 operation time.