ABNORMAL ENGINE NOISE DIESEL EXCESSIVE EXHAUST SMOKE

VEHICLES AFFECTED: 1982-83 'A' Series Vehicles Equipped With 4.3L V-6 Diesel Engines

CONDITION

Some 1982 and 1983 Oldsmobiles equipped with a V-6 diesel engine may experience excessive black exhaust smoke and abnormal engine noise after being driven several miles at highway speeds.

CAUSE

At highway speeds, crankcase blowby in the engine flows through the oil drain back holes in the block and cylinder head. This restricts oil return from the top of the cylinder head to the crankcase. The level of oil may increase on top of the cylinder head to the point it is drawn into the engine crankcase ventilation system. This will result in excessive exhaust smoke and engine noise. The oil level in the engine may be one pint to one quart low after this occurrence.

CORRECTION

1. Oil drawn into the engine may damage the ring land on a piston causing an increase in blowby. Remove the oil fill cap and see if there is excessive vapours coming out. If there is, perform a compression test on each cylinder to determine if there is piston ring land damage. Pistons with damaged lands must be replaced.

2. Following Service Manual procedures, remove the lifter and examine the lifter bore for any machining irregularities or any bore wear that will allow an increase in oil flow out of the top of the lifter bore.

3. Install valve lifters, Part No. 5234464 (standard) or Part No. 5234491 (.010 oversize). These lifters have reduced oil flow.

4. It is essential that a standard lifter not be installed in a .010 oversize bore. Put the lifter in half way and wiggle it. It should be tight.

5. Probe the four drain back holes in the lifter area of the block to make sure they are not plugged.

6. Examine the cast hole between the bolt holes for the lifter retainer. There should be no more than 1/8 inch of casting flash around the edge of the hole. Carefully break off and discard any extra flashing.

7. Install a new lifter retainer, Part No. 22522529.

8. Probe the oil drain back holes in each end of the cylinder head to a make sure they are not plugged.

9. Use care upon reassembly not to use too much RTV sealer on the intake manifold and valve cover. Engines that have standoff clips or dimples use a 1/4 inch diameter bead. Other engines use a 1/8 inch diameter bead. The use of excessive sealer may result in pieces of sealant plugging the oil drain back holes.

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.