For 1990-2009 cars

# EXHAUST PIPE KNOCKING NOISE (REPL. SPLASH SHIELD)

#### SUBJECT: EXHAUST PIPE KNOCKING NOISE (REPLACE WATER/SLUSH SPLASH SHIELD)

#### MODELS: 1985-90 BUICK ELECTRA 1985-93 BUICK PARK AVENUE 1986-93 BUICK LESABRE 1985-93 OLDSMOBILE NINETY EIGHT 1986-93 OLDSMOBILE EIGHTY EIGHT 1987-93 PONTIAC BONNEVILLE

********************************************************************** THIS BULLETIN CANCELS AND SUPERSEDES BULLETIN #106602. CADILLAC DEALERS -- CONTINUE TO USE BULLETIN T-92-86. **********************************************************************

PREVIOUS DIVISIONAL PUBLICATION NUMBERS WERE:

BUICK 92-6-6 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 ARE CURRENTLY AVAILABLE FROM GMSPO.

#### WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION NUMBER: L2398 LABOR TIME: .4 HR (FOR 1985-88 VEHICLES) .5 HR (FOR 1989-93 VEHICLES)

FIGURES: 1

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.

COPYRIGHT 1994 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.