DIESEL INFORMATION BULLETINS SEVERAL ITEMS COVERED

ENGINE MISS AND EXHAUST SMOKE AT HIGHWAY SPEEDS - 1982 AND 1983 V-6 DIESEL ENGINES (VIN CODE T)

An engine miss followed by a puff of blue smoke out the exhaust may be caused by engine oil leaking into the intake area of the cylinder head. The pipe-thread plugs that cover the upper Torx head bolts may be the source of an oil leak if not fully seated.

DIESEL INJECTION PUMP REPAIR PARTS

Diesel engine injection pump repair parts are now available through WDDGM. Repair parts available are listed in the current parts catalog groups 3.300 through 3.340.

MAIN BEARING BOLT HOLES - 1983 V-6 DIESEL ENGINE (VIN CODE "T")

Main bearing bolt hole thread pitch for #2 and #3 main bearings have been changed from 1.75mm to 1.76mm on V-6 diesel engines. The main bearing bolt has not changed. This results in an interference fit with the last few threads when the bolt is screwed into the hole. This interference spreads the load throughout the bulkhead rather than concentrating it at the surface. Engine blocks that have a main bearing bolt hole pitch of 1.76mm for #2 and #3 main bearings are identified by a stamped letter "G" behind the cast part number. The cast part number is located on the top rear of the block next to the oil pump drive assembly. When installing these bolts it is essential that engine oil be applied to the threads to prevent galling. It is normal for the bolt to tighten up slightly during the last few turns upon installation. Do not attempt to "clean up" #2 and #3 main bearings block threads by retapping with standard tap size M 12-1.75. The M 12-1.76 tap used is not a standard tap size.

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.