POPPING/SPARK KNOCK NOISE DRIVING UP MEDIUM GRADES. Pontiac Grand Prix 1996

REVISED: 05/18/95

THIS BULLETIN IS BEING REVISED TO CHANGE THE CORRECTION SECTION AND UPDATE EXHAUST SEAL AND RIGHT EXHAUST MANIFOLD PART NUMBERS. PLEASE DISCARD BULLETIN 476006 (FILED IN SECTION 6 - ENGINE). ---------------------------------------------------------------------- REVISION: 05/25/95

THIS BULLETIN IS BEING REVISED TO CLARIFY SUBJECT, CONDITION, CAUSE, AND PARTS INFORMATION SECTIONS. PLEASE DISCARD BULLETIN 47-60-06 (FILED IN SECTION 6 - ENGINE). ----------------------------------------------------------------------

REVISION: 10/16/95

THIS BULLETIN IS BEING REVISED TO ADD 1996 MODELS, ADD THE W CAR AND TO UPDATE PARTS INFORMATION SECTION. PLEASE DISCARD CORPORATE BULLETIN NUMBER 47-60-06A (SECTION 6 - ENGINE). ----------------------------------------------------------------------

REVISION: 03/27/96

THIS BULLETIN IS BEING REVISED TO ADD THE LQ1 ENGINE APPLICATIONS AND TO REVISE THE PARTS INFORMATION SECTION. PLEASE DISCARD CORPORATE BULLETIN NUMBER 47-60-06B (SECTION 6 - ENGINE). ----------------------------------------------------------------------

REVISION: 04/23/96

THIS BULLETIN IS BEING REVISED TO CORRECT THE LABOR OPERATION NUMBER. PLEASE DISCARD CORPORATE BULLETIN NUMBER 47-60-06C (SECTION 6 - ENGINE). ----------------------------------------------------------------------

SUBJECT: POPPING/FLUTTERING/TICKING/SPARK KNOCK/CLUNKING NOISE WHILE DRIVING UP MEDIUM GRADES OR ACCELERATING FROM A STOP (REPLACE EXHAUST SEAL)

MODELS: 1995-96 BUICK PARK AVENUE, RIVIERA 1996 BUICK LESABRE, REGAL 1995-96 OLDSMOBILE EIGHTY EIGHT, NINETY EIGHT 1995-96 PONTIAC BONNEVILLE WITH 3800 SERIES II ENGINE (VIN K - RPO L36)

1996 BUICK PARK AVENUE, RIVIERA 1996 OLDSMOBILE EIGHTY EIGHT LSS 1996 PONTIAC BONNEVILLE WITH 3800 SUPERCHARGED SERIES II ENGINE (VIN 1 - RPO L67)

1996 CHEVROLET LUMINA 1996 OLDSMOBILE CUTLASS SUPREME 1996 PONTIAC GRAND PRIX WITH 3.4L TWIN DOHC (VIN X - RPO LQ1)

CONDITION:

SOME OWNERS MAY DESCRIBE A CONDITION OF A POPPING, FLUTTERING, TICKING, OR SPARK KNOCK TYPE OF NOISE WHILE DRIVING UP MEDIUM GRADES OR ACCELERATING FROM A STOP. SOME OWNERS MAY DESCRIBE A CLUNKING TYPE NOISE THAT SEEMS TO ORIGINATE FROM THE REAR OF THE VEHICLE.

CAUSE:

THE ORIGINAL SEAL MAY BECOME MOMENTARILY SEIZED TO THE FRONT EXHAUST PIPE FLANGE. WHEN THIS HAPPENS, NORMAL ENGINE MOVEMENT MAY CAUSE THE FLAT SIDE OF THE SEAL TO MOVE AWAY FROM THE EXHAUST MANIFOLD. WHEN THE SEAL MOVES AWAY FROM THE EXHAUST MANIFOLD FLANGE, AN AUDIBLE EXHAUST NOISE MAY BE HEARD. ALSO, A POPPING NOISE MAY BE HEARD DUE TO THE SEAL SNAPPING BACK IN POSITION AND BANGING AGAINST THE EXHAUST MANIFOLD FLANGE.

CORRECTION:

TO DIAGNOSE THE CONDITION, SET THE PARKING BRAKE, START THE ENGINE AND RUN UNTIL OPERATING TEMPERATURE IS REACHED. ALTERNATELY PLACE THE GEAR SELECTOR IN DRIVE AND REVERSE THEN LIGHTLY LOAD THE ENGINE. LISTEN FOR NOISE AROUND THE EXHAUST SEAL AREA. THE VEHICLE MAY NEED TO BE RAISED IN THE AIR TO GAIN ACCESS FOR LISTENING AROUND THE ENTIRE SEAL AREA.

IF A NOISE IS DETECTED, REPLACE THE EXHAUST SEAL. THE REPLACEMENT SEAL IS MADE FROM A MATERIAL THAT IS LESS SUSCEPTIBLE TO SEIZING TO THE FRONT EXHAUST PIPE FLANGE AS COMPARED TO THE ORIGINAL SEAL. THE REPLACEMENT SEAL IS ALSO DESIGNED TO FIT SNUG AROUND THE EXHAUST MANIFOLD FLANGE TUBE.

*IMPORTANT* INSURE THE FLAT SIDE OF THE EXHAUST SEAL IS SEATED FIRMLY AGAINST THE EXHAUST MANIFOLD FLANGE.

PARTS INFORMATION

DESCRIPTION PART NUMBER

EXHAUST SEAL 24506449

PARTS ARE CURRENTLY AVAILABLE THROUGH GMSPO.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION DESCRIPTION LABOR TIME L2090 SEAL, FRONT EXHAUST USE PUBLISHED LABOR OPERATION TIME.

FIGURES: 0 ATTACHMENTS: 0

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.