ENGINE NOISE (REPL. WITH NEW DESIGN EXHAUST MANIFOLD). GMC Truck GMC C Pickup

REVISION: 11/04/94

THIS BULLETIN IS REVISED TO SPECIFY **CAST IRON** EXHAUST MANIFOLD SERVICE WITH NEW STAINLESS STEEL EXHAUST GASKET. PLEASE DISCARD BULLETIN 376602 (GROUP REFERENCE 6 - ENGINE). ---------------------------------------------------------------------- REVISION: 01/17/95

THIS BULLETIN IS BEING REVISED TO ADD 1994-95 MODEL YEARS AND UPDATE PARTS INFORMATION. PLEASE DISCARD BULLETIN 376602 (GROUP REFERENCE 6 - ENGINE). ---------------------------------------------------------------------- REVISION: 10/25/96

THIS BULLETIN IS BEING REVISED TO UPDATE THE CORRECTION INFORMATION STATEMENT AND ADDITIONAL SERVICE PARTS INFORMATION LISTED UNDER ALL MODELS. PLEASE DISCARD BULLETIN NUMBER 37-66-02A (GROUP REFERENCE 6--ENGINE). ----------------------------------------------------------------------

SUBJECT: ENGINE NOISE (REPLACE WITH NEW DESIGN CAST IRON EXHAUST MANIFOLD AND STAINLESS STEEL GASKET)

MODELS: 1982-95 CHEVROLET AND GMC C/K, R/V, G AND P TRUCKS WITH 7.4L ENGINE (VIN N - RPO L19) AND CAST IRON EXHAUST MANIFOLDS

IMPORTANT: THIS BULLETIN DOES NOT APPLY TO ENGINES WITH STAINLESS STEEL EXHAUST MANIFOLDS (OPTION H5D).

CONDITION:

SOME OWNERS MAY COMMENT ON AN ENGINE NOISE. THE NOISE IS NORMALLY LOUDEST WHEN THE ENGINE IS COLD.

CAUSE:

AN EXHAUST LEAK MAY HAVE DEVELOPED BETWEEN THE CAST IRON EXHAUST MANIFOLD AND THE CYLINDER HEAD MATING SURFACE. THE CAST IRON EXHAUST MANIFOLD HAS WARPED AT THE ENDS.

CORRECTION:

A NEW EXHAUST MANIFOLD, STAINLESS STEEL GASKET AND ATTACHING HARDWARD HAS BEEN DEVELOPED TO CORRECT THIS CONDITION. REPLACE THE EXISTING CAST IRON EXHAUST MANIFOLD AND GASKET WITH THE NEW DESIGN EXHAUST MANIFOLD, STAINLESS STEEL GASKET AND NEW ATTACHING HARDWARE. DISCARD THE EXISTING HARDWARE SINCE IT WILL NOT BE REUSED.

PART NUMBER DESCRIPTION MODEL YEAR QUANTITY ----------- ----------- ----- ---- -------- P, R, V MODELS -------------- 12551443 MANIFOLD ASSEMBLY--EXHAUST - RH P 82-95 1 12551443 MANIFOLD ASSEMBLY--EXHAUST - RH R/V 87-91 1 12551444 MANIFOLD ASSEMBLY--EXHAUST - LH P 82-95 1 12551444 MANIFOLD ASSEMBLY--EXHAUST - LH R/V 87-91 1

G MODELS

12551443 MANIFOLD ASSEMBLY--EXHAUST - RH 88-95 1 12551444 MANIFOLD ASSEMBLY--EXHAUST - LH 88-90 1 10223351 MANIFOLD ASSEMBLY--EXHAUST - LH 91-95 1

C/K MODELS ---------- 12551445 MANIFOLD ASSEMBLY--EXHAUST - LH 88-95 1 12551444 MANIFOLD ASSEMBLY--EXHAUST - LH 82-87 1 12551443 MANIFOLD ASSEMBLY--EXHAUST - RH 82-87 1 12523197 MANIFOLD ASSEMBLY--EXHAUST - RH 88-95 1

ALL MODELS

12551449 GASKET--EXHAUST MANIFOLD 2 12554867 STUD--EXHAUST MANIFOLD 15 9442946 NUT-EXHAUST MANIFOLD 15 3909821 BOLT EXHAUST MANIFOLD 1 9442958 NUT-SPARK PLUG HEAT SHIELD 8 14088834 STUD--EXHAUST PIPE (ENGLISH) 3 12337934 STUD--EXHAUST PIPE (ENGLISH) 3 15677737 STUD--EXHAUST PIPE (METRIC) 6 587575 SPRING--EXHAUST PIPE 6 9422297 NUT--EXHAUST PIPE (ENGLISH) 6 11516207 NUT--EXHAUST PIPE (METRIC) 6 15592451 SEAL--EXHAUST PIPE 2 10068600 SHIELD--STARTER 82-87 1 12337984 NUT--STARTER SHIELD (1/4 -20) 82-87 2

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION LABOR OPERATION: J0100 MANIFOLD, EXHAUST RH - REPLACE J0101 MANIFOLD, EXHAUST LH - REPLACE USE PUBLISHED LABOR OPERATION TIMES.

TROUBLE CODE 92.

FIGURES: 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.