INFO. ON ENGINE OIL LEAK IDENTIFICATION

SUBJECT: INFORMATION ON ENGINE OIL LEAK IDENTIFICATION AND REPAIR

MODELS: 1995 OLDSMOBILE AURORA WITH 4.0L ENGINE (VIN C-RPO L47)

THIS BULLETIN PROVIDES INFORMATION ON THE IDENTIFICATION OF ENGINE OIL LEAKS WHICH MAY APPEAR ON THE CRANKCASE AND OTHER AREAS OF THE ENGINE. THE FOLLOWING INFORMATION IDENTIFIES THE MOST COMMON AREAS OF OIL LEAKS AND THE REPAIR PROCEDURES TO CORRECT THEM.

**OIL FILTER ADAPTER**

LEAKS IN THIS AREA HAVE BEEN CAUSED BY CRACKS IN THE ADAPTER HOUSING DUE TO OVER TIGHTENING OF THE MOUNTING BOLTS AND/OR THE OIL COOLER LINE COUPLINGS. THE TORQUE ON THE OIL COOLER LINES IS 18 N.M (13 LBS. FT.).

1. USING AN APPROPRIATE TORQUE WRENCH, CHECK THE TORQUE ON THE LINES BEFORE TIGHTENING. DO NOT PLACE A WRENCH ON THE COOLER LINE FITTINGS AND TIGHTEN THE LINES UNTIL THEY BECOME SNUG. THIS CAUSES THE LINES TO BE OVER TORQUED, AND THE FITTINGS AND/OR O-RINGS TO BECOME DISTORTED. MULTIPLE REMOVAL AND INSTALLATION OF THE OIL COOLER LINES MAY ALSO DISTORT THE FITTINGS.

2. CAREFULLY INSPECT THE O-RINGS AND FITTINGS ON THE OIL COOLER LINES. IF THE O-RINGS APPEAR TO BE DAMAGED AND/OR FITTINGS APPEAR TO BE OUT-OF-ROUND, REPLACE THESE PARTS AS NECESSARY.

OIL MAY ALSO LEAK BY THE O-RINGS BETWEEN THE ADAPTER AND THE BLOCK.

1. WIPE THE CRANKCASE AND INSURE THE AREA IS CLEAN OF OIL.

2. CHECK FOR FLATNESS ON THE CRANKCASE SURFACE. IF THE SURFACE IS NOT FLAT, HONE THE SURFACE UNTIL AN ADEQUATE SEALING SURFACE IS OBTAINED. TO CORRECT LEAKS IN THIS AREA, REPLACE THE ADAPTER (P/N 12554107), O-RINGS, AND INSTALL BOLTS (P/N 3546520) WITH CONICAL WASHERS. TORQUE ON THE BOLTS WITH CONICAL WASHERS IS 16 N.M (12 LBS. FT.).

AMOJEL IS USED IN THE MANUFACTURING PROCESS TO KEEP ENGINE OIL IN THE ADAPTER HOUSING DURING THE SHIPPING PROCESS. AFTER THE INITIAL INSTALLATION OF THE OIL COOLER LINES AND TEMPERATURE CYCLING, AMOJEL MAY BE EVIDENT ON THE OIL FILTER AND ADAPTER. WIPE ANY RESIDUAL AMOJEL OFF THE OIL FILTER AND ADAPTER.

**REAR MAIN SEAL**

THE REAR MAIN SEAL MAY BE MISPOSITIONED DURING ASSEMBLY. IN THIS CASE, THE SEAL WILL BE CROOKED IN THE BLOCK. A PROPERLY INSTALLED SEAL SHOULD BE SEATED 0.3 MM BELOW THE SURFACE OF THE BLOCK FACE AROUND THE ENTIRE SEAL. AN ILLUSTRATION OF THE SEAL IN THE PROPER ORIENTATION CAN BE SEEN IN THE 1995 G CAR SERVICE INFORMATION MANUAL. TO REPAIR THIS CONDITION, INSTALL A NEW SEAL USING KENT MOORE TOOL J38817.

**CRANKCASE HALVES**

THERE ARE TWO COMMON REASONS FOR LEAKS IN THE CHANNEL BETWEEN THE UPPER AND LOWER CRANKCASE.

THE FIRST IS A CUT/DAMAGED SEAL, USUALLY AT THE ENDS. IF A LEAK IS EVIDENT IN THIS AREA, CLEAN THE CRANKCASE AT THE CASE HALVES, SPRAY FOOT POWDER AT THE SEAM AND DRIVE THE VEHICLE UNTIL THE ENGINE REACHES OPERATING TEMPERATURE. INSPECT THE CASE HALVES FOR EVIDENCE OF A LEAK. IF A LEAK AT THE OIL COOLER ADAPTER WAS PRESENT, AIRFLOW AROUND THE CRANKCASE WILL BLOW OIL FROM THE ADAPTER TO THE CRANKCASE SEAMS.

THE SECOND REASON IS THE LOWER CRANKCASE SEALING SURFACE MAY HAVE AN IMPERFECTION ON ITS SURFACE WHICH DOES NOT ALLOW PROPER SEALING OF THE SEAL.

**LIFTER GALLEY PLUG**

LEAKS AT THE REAR ENGINE AREA MAY HAVE BEEN CAUSED BY A CROSS THREADED OR LOOSE LIFTER GALLEY PLUG. TWO PLUGS ARE IN THE REAR OF EACH CYLINDER HEAD, WITH THE INBOARD PLUG LOCATED BEHIND THE COOLANT CROSSOVER. IF A LEAK IS FOUND, REMOVE PLUG AND INSTALL CORRECTLY. THE PLUG HAS SEALANT ON IT AND IS REUSABLE IF THE THREADS ARE NOT DAMAGED.

**CHAIN GUIDE ACCESS PLUG**

LEAKS AT THE FRONT OF THE ENGINE AREA MAY HAVE BEEN CAUSED BY A CROSS THREADED LOOSE CHAIN GUIDE ACCESS PLUG. TWO PLUGS (GRAY IN COLOR) ARE LOCATED AT THE FRONT OF EACH CYLINDER HEAD. THIS PLUG MAY HAVE BEEN CROSS THREADED DURING INSTALLATION. REMOVE THE PLUG AND INSURE CORRECT THREAD INSERTION DURING INSTALLATION.

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

FIGURES: 6 ATTACHMENTS: 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 OCCURRING 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 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.

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