THUMPING NOISE FROM THE MUFFLER CAN BE HEARD. Chevrolet Cavalier 1996

SUBJECT: THUMPING NOISE FROM THE MUFFLER CAN BE HEARD AT IDLE IN PARK OR DRIVE (REPLACE MUFFLER)

MODELS: 1995-98 CHEVROLET CAVALIER 1995-98 PONTIAC SUNFIRE 1995-98 TOYOTA CAVALIER WITH 2.2L ENGINE (VIN 4 - RPO LN2)

CONDITION:

SOME OWNERS MAY COMMENT THAT A THUMPING OR OIL CANNING NOISE MAY BE HEARD ON COLD OR HOT EXHAUST SYSTEMS. THIS NOISE CAN BE HEARD WHILE AT IDLE IN PARK OR DRIVE.

CAUSE:

CONDITION MAY BE CAUSED BY NOISE PRODUCED BY THE OUTER AND INNER MUFFLER SHELLS SEPARATING FROM DIFFERENT THERMAL EXPANSION RATES. THE OUTER SHELL USUALLY WILL BUCKLE IN THE REAR CHAMBER OF THE MUFFLER. PRESSURE PULSATION FROM THE ENGINE CAUSES THE OUTER SHELL TO RESONATE AND PRODUCE THE THUMPING NOISE.

IMPORTANT:

MUFFLERS BUILT AFTER OCTOBER, 1997 HAVE AN ADDITIONAL TWELVE SPOT WELDS ADDED TO PREVENT THIS CONDITION.

CORRECTION:

REPLACE THE MUFFLER WITH P/N 22614984 (CHEVROLET) AND P/N 22614985 (PONTIAC).

PARTS INFORMATION:

P/N DESCRIPTION ==================== ============================

22614984 (CHEVROLET) MUFFLER ASSEMBLY

22614985 (PONTIAC) MUFFLER ASSEMBLY

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION LABOR OPERATION NUMBER DESCRIPTION TIME =============== ========================= ================

L2584 MUFFLER - REPLACE USE PUBLISHED LABOR OPERATION TIME

FIGURES: 00

ATTACHMENTS: 00

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.