Bonneville V6-231 3.8L VIN 3 SFI (1988)
Heat Shield: Customer Interest
Exhaust Pipe - Knocking Noise
Group Ref.: 6 - Engine
Bulletin 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:
