REAR MAIN OIL LEAK DIAGNOSE / INSPECT CRANKSHAFT

Model and Year: 1987 CAPRICE, MONTE CARLO, EL CAMINO WITH 4.3L (CODE Z) ENGINE 1987 R, V, G, M TRUCKS WITH 4.3L (CODE Z) ENGINE 1988 C, K TRUCKS WITH 4.3L (CODE Z) ENGINE

Chevrolet Dealer Service Bulletin 88-10 (Section 6A) date April 1987 is being cancelled and superseded. This bulletin deletes the inspection for crosshatch machining marks and provides specific criteria for crankshaft replacement and specific instructions for assembling rear main oil seal.

Some 1987 and 1988 passenger cars, trucks and 1988 C/K model trucks equipped with 4.3L engines with engine build date codes prior to T1202 may experience a rear main oil seal leak condition due to a poor surface finish on the crankshaft sealing surface.

To diagnose this condition check the oil leak using an ultraviolet light and engine oil dye. If all of the following conditions are met replace the crankshaft and rear main oil seal.

1. Leakage is between the crankshaft sealing surface and crankshaft oil seal lip.

2. Engine build code is prior to T1202. (See explanation below).

3. Removal and inspection of the rear main oil seal indicates the seal is not torn.

If all of the above conditions are not met, replace only the rear main oil seal and retainer.

NOTICE: THE ASSEMBLY OF THE REAR MAIN OIL SEAL AND RETATNER MUST BE PERFORMED IN THE FOLLOWING SEQUENCE OR POTENTIAL FOR AN OIL LEAK AT THE REAR MAIN OIL SEAL EXISTS.

1. LOOSEN OIL PAN FASTENERS AND ALLOW OIL PAN AND OIL PAN SEAL TO FALL FREE OR REAR MAIN OIL SEAL RETAINER.

2. INSTALL NEW REAR MAIN OIL SEAL AND RETAINER. TORQUE RETAINER FASTENERS TO SPECIFICATION.

3. AFTER TORQUING RETAINER FASTENERS, TORQUE OIL PAN FASTENERS TO SPECIFICATION.

IF THIS PROCEDURE IS NOT FOLLOWED THE OIL PAN MAY INTERFERE WITH THE RETAINER AND NOT ALLOW THE REAR MAIN OIL SEAL TO CENTER ON THE CRANKSHAFT.

Engine build code determination - Engine date code location is shown in Figure 1. The build date codes may be found in this area and appear as shown in the following example:

T1202ABC

The first letter indicates the plant where the engine was manufactured. The next four numbers indicate the day of manufacture; in this case 12th month 2nd day, and the last three digits may be any broadcast code.

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.