TIMING CHAIN NOISE CONDITIONS (REPL. TIMING CHAIN. Buick Century 1994

REVISION: 04/14/98

THIS BULLETIN IS BEING REVISED TO CORRECT PARTS INFORMATION. PLEASE DISCARD CORPORATE BULLETIN 87-61-21 (SECTION 6-ENGINE). ______________________________________________________________________

SUBJECT: TIMING CHAIN NOISE CONDITIONS (REPLACE TIMING CHAIN)

MODELS: 1993-96 BUICK CENTURY 1992-97 CHEVROLET BERETTA, CAVALIER, CORSICA 1993-96 OLDSMOBILE CUTLASS CIERA 1995-97 PONTIAC SUNFIRE

1994-97 CHEVROLET AND GMC S MODELS 1996-97 ISUZU HOMBRE WITH 2.2L ENGINE (VIN 4--RPO LN2)

CONDITION:

SOME OF THE ABOVE NOTED VEHICLES MAY EXHIBIT A CLATTERING NOISE AT IDLE SPEED ORIGINATING FROM THE TIMING CHAIN AND FRONT COVER AREA. CHAIN WEAR IN EXCESS OF THE MAXIMUM TRAVEL OF THE TIMING CHAIN TENSIONER MAY CREATE NOISE THAT MAY BE OBJECTIONABLE TO SOME CUSTOMERS.

CAUSE:

LACK OF REGULAR MAINTENANCE, AS REFERENCED IN THE OWNER'S MANUAL AND THE RESULTANT LACK OF LUBRICATION AND BUILDUP OF DEPOSITS INSIDE THE ENGINE MAY ACCELERATE WEAR OF THE TIMING CHAIN. IN ADDITION, THERE IS A SMALL LUBRICATION HOLE IN THE FRONT OIL PASSAGE PLUG THAT COULD BECOME BLOCKED WITH DEBRIS IF PROPER ENGINE MAINTENANCE IS NOT FOLLOWED.

CORRECTION:

IF THE OWNER OF THE VEHICLE INDICATES A NOISE CONCERN, INSPECT THE TIMING CHAIN AND TENSIONER. IN ADDITION, CONFIRM OIL FLOW FROM THE FRONT OIL PASSAGE PLUG AND REPLACE THE TIMING CHAIN, TIMING CHAIN TENSIONER, AND BOTH THE CAMSHAFT AND THE CRANKSHAFT SPROCKET IF NECESSARY TO CORRECT THE NOISE.

SERVICE PROCEDURE:

1. USING AN ENGINE EAR J-39565 OR AN ENGINE STETHOSCOPE LISTEN TO THE AREA AROUND THE ENGINE FRONT COVER AND TIMING CHAIN. IT MAY BE HELPFUL TO COMPARE ANY NOISES WITH A VEHICLE THAT IS KNOWN TO HAVE GOOD OR NEW TIMING CHAIN AND TENSIONER COMPONENTS. TIMING CHAIN NOISE IS MOST OFTEN NOTED AS A RATTLE OR TICK AT IDLE SPEED THAT GOES AWAY AT HIGHER RPM. IF THE OWNER HAS A CONCERN WITH ENGINE NOISE AND IT DOES NOT APPEAR TO BE RELATED TO THE TIMING CHAIN, REVIEW ANY SERVICE BULLETINS RELATED TO ENGINE NOISE AND SERVICE MANUAL DIAGNOSTICS RELATED TO ENGINE NOISE CONDITIONS.

2.IF TIMING CHAIN NOISE IS GREATER THAN NORMAL, REMOVE THE ENGINE FRONT COVER USING PROCEDURES OUTLINED IN SECTION 6A2 OR THE ENGINE SECTION OF THE APPROPRIATE SERVICE MANUAL.

3. INSPECT THE TIMING CHAIN SYSTEM FOR WEAR BY MEASURING THE DISTANCE BETWEEN THE HOLE IN THE TENSIONER BRACKET AND THE UNWORN SURFACE OF THE TENSIONER SHOE.(SEE FIGURE 1) IF THE DISTANCE BETWEEN THE HOLE AND THE TENSIONER SHOE SURFACE IS MORE THAN 8 MM (0.314 IN.), REPLACEMENT OF TIMING COMPONENTS IS NECESSARY.

4. TURN THE CRANKSHAFT SO THAT THE TIMING MARKS ON THE CRANKSHAFT SPROCKET AND THE CAMSHAFT SPROCKET ARE ALIGNED WITH THE TABS ON THE TIMING CHAIN TENSIONER BRACKET. (SEE FIGURE 2)

5. REMOVE THE TIMING CHAIN TENSIONER, TIMING CHAIN, AND BOTH SPROCKETS USING THE PROCEDURES OUTLINED IN SECTION 6A2 OR THE ENGINE SECTION OF THE APPROPRIATE SERVICE MANUAL.

6. AFTER REMOVING THE TIMING CHAIN, TENSIONER, AND SPROCKETS, INSPECT THE CUP PLUG BEHIND THE TIMING CHAIN FOR SIGNS OF OIL FLOW (SEE FIGURE 3). THE CUP PLUG HAS AN ORIFICE APPROXIMATELY 1MM (0.039IN.) IN DIAMETER. IF THE PLUG APPEARS DRY OR THE ORIFICE APPEARS TO BE BLOCKED WITH DEBRIS, INSERT THE PULLER END OF SLIDE HAMMER J 6471-02 OR EQUIVALENT INTO THE CUP PLUG AND REMOVE IT.

7. AFTER CLEANING ANY DEBRIS FROM BEHIND THE CUP PLUG, INSTALL A NEW CUP PLUG, GM P/N 14033197, INTO THE OIL PASSAGE. IMPORTANT: THE CUP PLUG MUST BE REPLACED WITH GM P/N 14033197. THIS PLUG HAS A SPECIFICALLY SIZED LUBRICATION HOLE FOR THE TIMING CHAIN. IF ANY OTHER PLUG IS USED, THERE MAY BE A REDUCTION IN ENGINE OIL PRESSURE TO THE VALVETRAIN OR A LACK OFLUBRICATION FOR THE TIMING CHAIN AND TENSIONER COMPONENTS.

8. AFTER THE CORRECT CUP PLUG IS INSTALLED IN THE OIL PASSAGE, INSTALL A NEW TIMING CHAIN, TENSIONER, AND SPROCKETS USING PROCEDURES OUTLINED IN SECTION 6A2 OR THE ENGINE SECTION OF THE APPROPRIATE SERVICE MANUAL.

SERVICE PARTS INFORMATION:

DESCRIPTION P/N ----------- --- PLUG, ENGINE OIL GALLERY 14033197 SPROCKET, CRANKSHAFT 10083171 SPROCKET, CAMSHAFT 1992 AND 1993 10083170 SPROCKET, CAMSHAFT 1994 AND LATER 10198810 CHAIN, CAMSHAFT TIMING 24576828 TENSIONER, TIMING CHAIN 12363192

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR VEHICLE LABOR OPERATION DESCRIPTION SERIES TIME --------- ----------- ------- ----

J0840 SPROCKET CAMSHAFT TIMING - S-TRUCK 1.4 HRS REPLACE

J0840 SPROCKET CAMSHAFT TIMING - J-CAR 3.4 HRS REPLACE 1992-94

J0840 SPROCKET CAMSHAFT TIMING - J-CAR 4.5 HRS REPLACE 1995-97 ADD: FOR VEHICLES WITH A/C 0.3 HR

J0840 SPROCKET CAMSHAFT TIMING - L-CAR 3.8 HR REPLACE ADD: FOR VEHICLES WITH A/C 0.3 HR

J0840 SPROCKET CAMSHAFT TIMING - A-CAR 4.3 HR REPLACE

TO CLEAN PARTS ON VEHICLES OVER 30,000 MILES IF NECCESSARY, ADD 0.2 HR.

FIGURES: 3 ATTACHMENTS: 0

FIGURE 1: TIMING CHAIN WEAR MEASUREMENT

FIGURE 2: TIMING MARK ALIGNMENT

FIGURE 3: OIL PASSAGE PLUG

Object Number: 335930 Size: SH

Object Number: 335932 Size: SH

Object Number: 335934 Size: SH

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.