METALLIC KNOCK SOUND WHEN ENGINE COLD(REPL. PISTON/ENG.). Buick Roadmaster 1992

********************************************************************* CONDITION: SOME OWNERS OF 1991-92 B AND D CARS EQUIPPED WITH 5.7L V8 ENGINES (RPO L05 - VIN 7) MAY COMMENT OF ENGINE COLD "PISTON SLAP" NOISE. THIS BULLETIN COVERS ALL 1991 AND 1992 PRODUCTION THROUGH MAY OF 1992.

NOTE: THIS NOISE WILL NOT RESULT IN ENGINE FAILURE, BUT MAY BE A CUSTOMER ANNOYANCE CONDITION.

ENGINE COLD "PISTON SLAP" MAY BE DESCRIBED AS: A METALLIC "KNOCK" SOUND THAT DIMINISHES AS THE ENGINE WARMS UP. THE KNOCK SOUND IS MOST NOTICEABLE AT 1500 THROUGH 2000 ENGINE RPM, WITH THE ENGINE AT A LIGHT LOAD. DURATION OF THE "KNOCK" VARIES DEPENDING ON THE ENGINE BLOCK TEMPERATURE. TEMPERATURES OF 40 DEGREES F OR LESS MAY RESULT IN A KNOCK DURATION AS LONG AS 5 TO 8 MINUTES. INTENSITY OF THE KNOCK WILL BE DEPENDENT UPON THE PISTON/CYLINDER BORE FIT AND BLOCK TEMPERATURE.

CAUSE:

IMPROPER PISTON/CYLINDER BORE FIT.

CORRECTION:

VERIFY THAT THE "PISTON SLAP - ENGINE COLD" CONDITION IS CORRECTLY IDENTIFIED.

TWO METHODS OF RESOLVING THIS PROBLEM ARE AVAILABLE.

PREFERRED METHOD: A 5.7L V8 (VIN 7) "GOODWRENCH" ENGINE ASSEMBLY ---------------- (FOR PASSENGER CAR APPLICATION ONLY) HAS BEEN RELEASED TO ADDRESS THIS CONCERN:

DESCRIPTION PART NUMBER ----------- ----------- 5.7L V8 GOODWRENCH ENGINE 12513151 ASSEMBLY (PASSENGER CAR)

NOTE: ON "D CAR" APPLICATIONS, REMOVE THE OIL PAN FROM THE ORIGINAL ENGINE AND INSTALL IT ON THE GOODWRENCH ENGINE ASSEMBLY.

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

BODY TYPE LABOR TIME CODE TIME --------- --------------- ---- B BODY J-1840 8.6 HOURS W/ENGINE OIL COOLER 0.2 HOUR

D BODY J-1840 USE PUBLISHED LABOR TIME CODES AND TIMES

OPTIONAL METHOD: REPLACE THE "SLAPPING" PISTON(S) WITH NEW --------------- PISTONS OF IMPROVED DESIGN. PISTONS ARE AVAIL- ABLE IN "STANDARD" AND "HIGH LIMIT" SIZES AS FOLLOWS:

DESCRIPTION PART NUMBER ----------- ----------- PISTON/STANDARD SIZE 10159436 PISTON/HIGH LIMIT SIZE 10159437

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION: USE STANDARD LABOR TIME CODES AND TIMES.

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS ONLY. BULLETINS ARE WRITTEN TO INFORM THOSE TECH- NICIANS OF A CONDITION POSSIBLY OCCURRING ON A VEHICLE, OR TO PROVIDE INFORMATION ASSISTING IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS, AND TRAINING TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THE BULLETIN APPLIES TO ALL VEHICLES. SEE AN AUTHORIZED GM DEALER FOR INFORMATION ON WHETHER A SPECIFIC VEHICLE MAY BENEFIT FROM THE INFORMATION.