COLD ENGINE TICK OR RATTLE AFTER AFTER START-UP. Buick Skylark 1996

REVISION: 06/11/98 DIVS INVL 1 2 3 4 7

THIS BULLETIN IS BEING REVISED TO EXPAND THE MODEL YEAR COVERAGE, AND TO ADD THE U-VAN, THE 3400 V6 ENGINE APPLICATIONS AND PARTS INFORMATION. ALSO, THE CAUSE STATEMENT HAS BEEN CHANGED. PLEASE DISCARD CORPORATE SERVICE BULLETIN 57-61-24 (SECTION 6-ENGINE). ______________________________________________________________________

SUBJECT: COLD ENGINE TICK OR RATTLE AFTER START-UP (REPLACE PISTON/PIN ASSEMBLY)

MODELS: 1994-95 BUICK REGAL 1994-97 BUICK SKYLARK 1994-98 BUICK CENTURY 1994-95 CHEVROLET BERETTA, CORSICA, LUMINA, MONTE CARLO 1996-98 CHEVROLET VENTURE 1997-98 CHEVROLET MALIBU 1993-97 OLDSMOBILE CUTLASS SUPREME 1994-96 OLDSMOBILE CUTLASS CIERA 1994-97 OLDSMOBILE ACHIEVA 1997-98 OLDSMOBILE CUTLASS 1996-98 OLDSMOBILE SILHOUETTE 1994-98 PONTIAC GRAND PRIX 1994-98 PONTIAC GRAND AM 1996-98 PONTIAC TRANS SPORT WITH 3100 OR 3400 V6 ENGINE (VINS M, E - RPOS L82, LA1)

CONDITION:

SOME CUSTOMERS MAY COMMENT ON A TICKING TYPE NOISE THAT BEGINS SHORTLY AFTER COLD ENGINE START-UP AND GRADUALLY DIMINISHES AS THE ENGINE WARMS UP. IN MOST CASES, THE NOISE IS GONE AFTER FIVE (5) MINUTES. IN SEVERE CASES, THE NOISE MAY NOT DISAPPEAR WHEN THE ENGINE IS HOT.

CAUSE:

UNDER NORMAL DESIGN TOLERANCES WHEN THE PISTON PIN BORE IS PRODUCED AT THE MAXIMUM TOLERANCE AND THE PISTON PIN IS PRODUCED AT THE MINIMUM TOLERANCE (MIN-MAX TOLERANCE) TRACE NOISE LEVELS CAN OCCUR. THIS LEVEL OF NOISE DOES NOT AFFECT THE RELIABILITY OR DURABILITY OF THE PRODUCT.

CORRECTION:

IF PISTON-TO-PIN NOISE IS DETECTED AND THE CUSTOMER DESIRES THE CONDITION TO BE CORRECTED, REPLACE ALL SIX PISTONS WITH PIN ASSEMBLIES. THE NEW PISTON SETS HAVE A MINIMAL PISTON-TO-PIN CLEARANCE. REMEMBER, PISTON-TO-PIN NOISE OCCURS IN BOTH PARK AND DRIVE AT ENGINE IDLE RPM AND IT VARIES IN INTENSITY DEPENDING ON THE NUMBER OF PISTONS INVOLVED. A TICKING SOUND MEANS ONE PISTON IS AFFECTED WHEREAS A RATTLE OR DIESEL TYPE SOUND INDICATES MORE THAN ONE PISTON AFFECTED. THE FOLLOWING SHOULD ALSO BE CHECKED:

1) ON W-CARS, MAKE SURE THE RIGHT SIDE ENGINE SPLASH SHIELD IS NOT CONTACTING THE ENGINE CRANKSHAFT BALANCER. THIS CONDITION USUALLY HAPPENS COLD AND IS CAUSED BY THE SHIELD CURLING WHEN COLD.

2) REFERENCE SERVICE BULLETIN 57-71-06 FOR TRANSMISSION RATTLE NOISE OFTEN CONFUSED FOR ENGINE RATTLE NOISE.

3) REFERENCE SERVICE BULLETIN 47-61-36 FOR ACCESSORY DRIVE BELT TENSIONER NOISE.

4) CHECK CYLINDER BORE DIAMETER AND PISTON DIAMETER AS OUTLINED IN THE SERVICE MANUAL.

IMPORTANT: EXCESSIVE CYLINDER BORE TO PISTON DIAMETER CLEARANCE CAN CAUSE A SIMILAR TYPE NOISE.

USE THE PROCEDURE IN THE APPROPRIATE SERVICE MANUAL FOR PISTON REPLACEMENT.

NOTICE: WHEN INSTALLING THE NEW PISTON AND PIN ASSEMBLY ONTO THE EXISTING RODS, USE EXTREME CARE TO AVOID DAMAGE TO EITHER THE PIN OR PISTON BORE. IF DAMAGE TO THESE AREAS OCCURS, THE NOISE WILL RETURN BECAUSE THE DAMAGE WILL CAUSE WEAR AND EXCESSIVE CLEARANCE.

PARTS INFORMATION:

DESCRIPTION P/N QTY APPLICATION ----------- --- --- -----------

PISTON WITH PIN ASSEMBLY 24505806 6 94-95 3100

PISTON WITH PIN ASSEMBLY 24508726 6 96-98 3100

PISTON WITH PIN ASSEMBLY 24508727 6 96-98 3400

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION LABOR OPERATION NUMBER DESCRIPTION TIME ---------------- ----------- ---------------

J1307 PISTON, ROD AND/OR RINGS USE PUBLISHED LABOR OPERATION TIME

FIGURES: 0 ATTACHMENTS: 0

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