Smoking 328 only when flat out

Can someone please help. I have a 1988 328 which runs fine under normal driving conditions. No smoke , no leaks etc. However when I open it up and go faster than 120mph a plume of grey smoke comes out the exhaust so thick I cannot see the road behind. When I back off the smoke disappears and everything returns to normal. I pulled over once and discovered a pool of oil underneath the oil cooler which had obviously been dripping onto the exhaust pipes but not enough to produce the volume of smoke that I saw! It was almost as if oil was being pumped directly into the cylinders!! When I drive the car normally it runs fine. Any ideas please?

Chris Dann jacquidann@hotmail.com

Hi Chris,

Doesn't sound good. Could be rebuild time.

You need to run some tests that will give you insight into internal engine condition.

Start with a compression test and follow up with a cylinder leakage test. Ir's possible one or both of the tests will reveal the source of the problem/s. If both tests reveal nothing that could give insight to the problem let us know.

Regards, JRV

I agree with JRV Chris, could well be a piston ring problem there. Cylinder leakage test would show loss of pressure into the crankcase. You may want to check the full enrichment operation of the fuel system as well if the other tests don't put up the red flag.

Brian

Hi Chris, This reminds me of a similar problem I had with my Mondial QV. Terrific thick smoke at high road speeds with no apparant engine problems. It turned out to be a split rubber gaitor on one of the drive shafts, when the shaft rotated fast enough, the grease inside the gaitor would fly out and deposit itself onto a hot exhaust and vapourising immediately creating smoke enough to give you a heart attack. Check them out, Cheers, Mario.

Dear JRV and Brian Stewart
Firstly, many thanks for your response to my problem with my 328. I have done a compression test and everything is fine with good compression and no leakage on all cylinders. I have a feeling that the problem lies with the oil cooler. When I drive the car normally i.e. some really hard acceleration, fast driving etc. the car runs fine, it does not use oil or burn oil and it pulls clean and strong with no smoke either on acceleration or de-celeration. The problem only starts when I take it above 100 - 120mph. After a few minutes of sustained driving at,say, 130mph I see thick grey smoke behind and oil under the oil cooler over the drive shaft and exhaust. When I back off it takes a few minutes for the smoke to diminish and everything returns to normal. Any clues please? If the oil cooler is leaking onto the exhaust would that produce the volume of smoke I describe?
Kind regards Chris Dann

Perhaps, under the extreme condition you describe, oil pressure is very high and the oil may seep out if there a minor leak somewhere in the cooler , lines, or fittings. Just a guess.

clean off the area really well, then run for a while, if there is a leak, should have some sign even at idling speeds. also check the drain hose on the rear head by the distributor, they often fail and could leak onto that area. If you can twist or move the hoses on the fittings at the oil cooler, they are probably due for repair. you can rebuild those fairly cheaply.
regards, Brian

Chris, I just had a similar problem. The car ran fine until I hit the highway, then the smoke started. When I pulled over to look at it, I had white smoke and dripping oil. It turned out the oil cooler had been rubbing against the ductwork and had worn a hole in the connection. At speed, the airflow was blowing the oil onto the muffler, causing the smoke. I replaced the oil cooler, no more problems. FYI, the cooler was only ~$250 from the owners site, was over $400 in the US.

Many thanks for your help guys. It turned out to be a split in the drive shaft gaitor which was throwing grease onto the exhaust at high speed. I replaced the gaitor and, hey presto! no more smoke. Thanks once again. Chris Dann (Spain)