My 1987 560SL has been running perfectly without even a drop of oil consumption. I don't drive it much, but I do take it out for a spin at least once per month. Today was a real bummer for me. Here's what happened.

I started the engine while the vehicle was in the garage. She started up on 1st fire as it always has. I let it warm up a little before I pulled it out in the driveway. I let it keep running and warm up while I got out and started to sweep the garage floor. After about 7 minutes of running, all of a sudden out of nowhere a huge amount of black smoke pored out of the exhaust. Then a huge cloud filled the garage within moments. I rushed to the car and shut her down. I let it cool down a bit (not that it was hot). I then restarted her and smoke was everywhere. The engine itself sounds just fine. No starnge noises or anything like that. I backed her into the garage and shut her down. When I did, I noticed at least a quart of oil had spilled out on the driveway. I got out my jack and lifted the car to see if I could see where it was all coming from. What I found was oil leaking right out of the exhaust pipe where the left and right exhaust pipes collect into one.

Does anyone know what could cause this abrupt oil blow? I've ruled out things like a head gasket as they just don't fail out of nowhere and specially not as severe as this and I would have probably found coolant. It was just sitting there idling! The week before I drove it around without any problems at all. It just doesn't make sense to me. Could it be some kind of vacuum problem that may suck oil in like that? I did notice the engine reving on it's own when this happened, but nothing more than that. I am stumped!

Any clues on where to start looking would be appreciated.

Thanks,
Tony

Not a good sign!!

I would pull the plugs and see if one is covered with oil. If such is the case I would look to the valve guides on that cylinder. I suppose there has to be other possibilities but the first that comes to mind is a dropped valve guide.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Next week if I get a chance I'll pull the plugs. A dropped valve guide certainly makes sense. Too bad because I haven't torn an engine apart since the 70's. I'm not sure I can remember. Like everything else on this car I'm sure rebuilding the heads is going to be super expensive...

I'll let you know what I find.

Black smoke? It sounds like the fuel mixture was pegged on full rich! Are you sure it was oil leaking out of the exhaust joint?

Yes, it was absolutely oil. About a quart if you can believe that. No sign of fuel at all and the smoke didn't smell rich like fuel. It was burning oil. This week I'll pull out the plugs and start digging deeper, but I'm sure stevebfl is right on track with his assumption. Too bad too because I just love this car. But for a few hundred bucks it should be back in service again.

Well I pulled each and every spark plug and there is no sign of oil on any of them. In fact their burn looks excellent. So I thought possibly it has been too long since this happened and the oil was gone so I started her up again. First click and she started as usual. I ran her for a few minutes without any sign of smoke. The engine is super quiet (quieter than my new Toyota) and sounds strong. Then suddenly the smoke appeared again and I found oil leaking out of the exhaust where the exhaust collector is. I shut her down and pulled every plug again and found no signs of oil what-so-ever!

So I'm a little confused at this point since oil is no where to be found other than the exhaust. I don't believe it could be a piston ring as that too would show up oil on the spark plug. And wouldn't a dropped valve guide hit the piston or at least make some kind of noise and put some oil in the spark plug area? The oil is getting into the exhaust in some other way. The smoke I see is probably just the oil getting heated up in the exhaust and then burning rather than being burnt from spark plug fire. After all, it takes several minutes before there is any sign of smoke.

So what can cause oil to make it to the exhaust but not into the heads? Could this be an exhaust valve guide or just a simple valve seal or something else? I'm not too familiar with the diagnoses process. My manual totally sucks so it's no help either and is usually best kept on the shelf anyway.

Last year I had an issue I was not able to solve. I took it to a place that is suppose to be "the place" for 107's and they even say they specialize in SL's, but they couldn't figure it out. I then took it to Mercedes who also charged me an arm and a leg and they didn't solve the issue either. However after weeks of having this problem pick at my brain, I solved the issue myself and found the problem was nothing but a faulty sensor. So as you can see, I don't trust the so called "experts" around here. They're only interested in getting a paycheck and don't seem to take pride in what they do.

Any ideas on what I should do next?

I would suspect an exhaust valve guide.
The oil would drain in the exhaust manifold out of the engine head without going into the combustion chamber, mix with the hot exhaust and burn on it's way out.
A long shot,......

Beat me to it. Definitely sounds like an exhaust guide. Thats why it probably takes a bit to smoke. It won't smoke till the exhaust gets hot enough for the oil in it to burn. If it were burning in the cylinder it would smoke immediately.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I agree, oil is by-passing the cylinder and right on out through the exhaust valve. Well it looks like I have some work cut out for me. If you're going to fix it, you might as well rebuild them both. Maybe I'll wait until fall to dive into it. I'm tired of working on this beast for now. I did a complete frame off suspension rebuild this last fall. I also rebuilt the entire braking system as well as the fuel system and replaced everything from the injectors back to the tank. Spent a ton of money, got several stitches in my hand and I still haven't had much drive time. After I fix the head problem and put in a new tranny (reverse slams from park/nuetral) and torque converter, it will be up for sale. One thing I'm a little concerned about is that I purchased a new Mercedes catalytic converter (go on and ask what that cost) and now it's full of oil. I sure hope this problem doesn't destroy that.

Pull the valve covers one of the guides must be broken,jumping up and down on the valve stem,I cant see that much oil from a warn guide. JNT

What was the issue? I have a Ford engine that the same exact occurrence happened to me at idle and I'm stumped.

Not being familiar with the architecture if this engine, these are guesses:

1) valve stem seal. Actually, not likely given that it doesn't happen at startup

2) clogged breather. When pressure builds in the crankcase, it follows the path of least resistance

3) cracked head

4) headgasket

had similar mysterious smoking with sudden onset, and it turned out to be the vacuum modulator valve on the transmission leaking into the intake manifold. I rebuilt the head, TWICE, in the absence of anyone able to advise me to check this. With smoking issues this should always be checked. The smoke is neither white or black but stinky grey..and pumps huge volumes! (95 E30 with M104 engine)

I don't know if this is the easiest method, but if you pull the exhaust manifold you should be able to identify if it is isolated to a particular cylinder, which would point to a valve guide.

__________________
Prost!

Check all the vacuum lines and breather hoses to see if it's simply aspirating the oil through the intake. Could be some sort of PCV issue causing oil to get sucked in to the intake. Sounds more severe than that, but it is an easy check and should be looked at before you tear into the top of the motor.

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition