Exhaust Pipe - Knocking Noise
Group Ref.: 6 - EngineBulletin No.: 436602
Date: August, 1994
SUBJECT:
EXHAUST PIPE KNOCKING NOISE
(REPLACE WATER/SLUSH SPLASH SHIELD)
MODELS:
1985-90 BUICK ELECTRA
1985-93 BUICK PARK AVENUE
1986-93 BUICK LE SABRE
1985-93 OLDSMOBILE NINETY EIGHT
1986-93 OLDSMOBILE EIGHTY EIGHT
1987-93 PONTIAC BONNEVILLE
THIS BULLETIN CANCELS AND SUPERSEDES BULLETIN # 106602 PREVIOUS DIVISIONAL PUBLICATION NUMBERS WERE:
Buick 92-6-6
Cadillac T-92-86
GM of Canada 92-6-109
Oldsmobile 92-T-53
Pontiac 92-6-27
CONDITION:
Some owners may comment on an exhaust pipe knocking noise.
CAUSE:
On some of the above vehicles, it is possible to have a condition of the exhaust pipe contacting the intermediate heat shield, which is located between the exhaust pipe and the floor panel. This condition could occur when water or slush is splashed onto the underside of the exhaust pipe. The rapid cooling and resultant contraction may cause the pipe to bow upwards making contact with the shield above it.
It is possible that the knocking noise could be transmitted to the engine through the exhaust pipe. This could be picked up by the ESC knock sensor which, in turn, would signal the ECM (by lack of voltage), causing it to respond with retarded ignition timing, thinking the engine has a detonation condition.
CORRECTION:
For 1985-1988 Vehicles - (See Illustration)
1. Install exhaust system water/slush splash shield kit, P/N 12536786, which consists of one piece.
2. Install the shield with two stainless steel clamps and the existing front bracket.
For 1989-1993 Vehicles - (See Illustration)
1. Install exhaust system water/slush splash shield kit, P/N 12536786.
2. Notch the shield to clear the cross brace welded to the exhaust pipe. Install with two stainless steel clamps and the existing front bracket.
PARTS INFORMATION:
Parts are currently available from GMSPO.
WARRANTY INFORMATION:
For vehicles repaired under warranty, use:
Labor Operation Labor Time
L2398 0.4 hr (For 1985-88 vehicles)
0.5 hr (For 1989-93 vehicles)