Heavy Smoke, at Times
 

My car normally has a clean smoke-free exhaust, except for some times in the morning while the engine is still cool. One route to work goes down a short steep hill with a stop at the bottom. When I accelerate from there, heavy clouds of blackish grey oil smoke pollute the air for a few hundred yards. Then it clears up. If I take another route that avoids the hill, there is no smoke at all.

What mechanically causes this? A combination of worn valve seals and a downward angle? Oil pump issues?

Most likely the valve guides or seals. Try shifting into N when approaching the hill & coasting down, if you have LESS smoke you can bet on the seals.

We have the same car (and my 380SE is also blue). I replaced all the valve stem seals about 2 years ago. Since, last summer, I had a problem with oil fouling the plug on #8 cylinder. Upon going back in and doing the seals on this cylinder again, assuming I had not seated one of them properly before, I noticed that the ridge on the valve guide that holds one of the seals in place was distorted. I pushed both on hard and buttoned it up, with no recurrance of fouling until last month.
Just about a week prior to this second fouling episode, I was going down a hill, stopped at the bottom at the stop sign, and got a huge plume of blue smoke when I accelerated into traffic.
This time, I just changed the plug, figuring that pulling the head to replace the valve guide wasn't worth the trouble. I havn't seen any blue smoke since either. I'll be following this thread to see if anyone contributes a good theory though.

Do you think all that smoke is from one cylinder? To me, it almost seems like oil is collecting on some flat surface, then the downhill angle is dumping it all into the intake. I don't notice much engine braking going down the hill, but I'll try shifting to N next time to see if it changes.

Well the problem smoke is still happening, and more often - about once a day now. As before, the exhaust is normally smoke-free. Just at times, after taking a fast turn or going down a hill, it makes big embarrassing trails of smoke for about a minute, then clears up. It doesn't make much difference if I put it in neutral going down hill. If anyone knows the internals of this engine, is there some place where oil could be collecting and then "spilling over" into the intake, or getting sucked in somehow?

Problem is still happening at random times about a minute or 2 after starting, but not every time. The car would run clean, then the engine will start chugging and missing slightly and the smoke starts spewing out the back. After a minute or so its fine again.

I don't know what to rule out or check. It just seems like a sudden dose of oil getting into one or more cylinders somehow.
Any hints appreciated.

I had a 1973 450SE that did this. It would get so bad during the warmup cycle it looked like the car was on fire from the rear. It would foul #3 plug about once a month. I replaced valve stem seals on that cylinder, and the problem persisted for about another three days, then just went away. I drove another 50,000 miles before selling the car.

Could be valve stem seals. If you never had the heads done before the 220k mile mark, now's probably the time. You may even have a few loose/broken guides that cause this.

Thanks. I wanted to try and find something external before pulling parts off the engine. But next warm day I will do just that. I've also started reading up on oiler tubes.

Had a problem like this when I first got my 500SEL. Turned out to be the modulator valve on the transmission. It has a vacuum line hooked to it and it was pulling trans fluid up this line and burning it. Fix was to replace the modulator valve.

Paul