Hello all.

I have a strange problem that I'm trying to diagnose.

I have a 1993 600SEL sedan with 85k miles. The car has an excellent service history and appears to have been well cared for. Was a starmark car until '03.

I just purchased the car and I never noticed any smoking issue when I was inspecting it. The car intermittantly smokes. It does not smoke when cold, but after driving it for about 20-25 minutes , it starts to smoke. Sometimes quite profusely. The smoking stops on its own too... When it isn't smoking , it runs great , smooth idle, etc..

The smoke is a white/greyish color. It doesn't smell like coolant. The car does not over heat and I haven't noticed any crankcase oil contamination.

Thus far, I've tried temporarily disabling the EGR, to no avail.

It seems like something is contaminating the intake and causing the smoke. Is it possible that the brake booster could draw brake fluid through a defective check valve?

Any ideas would be sincerely appreciated.

Herbert Phillips

The trans is overfilled.

Is it possible that the vaccum line to the modulator could be drawing trans fluid in to the intake?

The trans looks to be 3-4 quarts overfilled.

I'm guessing that when I drive the car, the transfluid is frothing and that the modulator is catching some of it and sending it through the intake?

What is the likelyhood of this?

By all means reduce the oil level in the tranny to the correct level--HOT. You might consider changing it since it has been severely stressed with air entrainment and probable overheating.

The vacuum lines to the transmission will not injest oil unless the seal in the transmission device is ruptured. There are two--one is the shift modulator (left side of tranny) and the other is the upshift delay device on the right (passenger) side. The upshift delay vacuum is only activated on a cold start and then for a couple of minutes. It holds the tranny in 2nd to a higher RPM for faster catalyst warm-up.

Easy to test--simply remove the hose at the tranny end and see what comes out. Should be clean--no oil. If ANY oil present, that device is faulty.

I was wrong about the modulator valve, it was fine. My issue is oil in the intake.

I saw oil in one of the vacuum lines that goes to the ignition control module on the left fender (driver). The oil was pulsing through the line. The line is a transparent/red vacuum line that plugs into the intake.

So, being curious , I removed the intake manifold. The manifold was full of clean crankcase oil. It was pooled up in the intake wells. More so on the right (passenger) bank, where the vacuum lines plugged in.

So , I have some sort of crankcase vent problem I think. I also noted an aftermarket catalytic converter under the car. Could this cause back pressure? Any clues?

What would cause the intake to have oil in it? The oil seperator unit that runs between the valleys was dry and didn't show signs of oil (at all), like it wasn't collecting the oil that it should. What feeds it?

Anyone have experience with the 120 motor?

the car has low miles, 85k and a super service history. Has not been abused.

Somehow I'm getting oil in my intake and it's being burned. Anyone know how this would happen?

I bought a copy of WIS on ebay for $40. Not a bad deal. Was difficult to get it working but, found a bulletin for the 119 motor that said "air injection dampner flap" was mislodged, and that it caused lots of blue smoke and that it would fill the exhaust with oil. This seems to be in line with my problem, anyone know anything about the air injection / crankcase ventilation on the 120 motor?

Having the same problem. My thoughts are a leak at a gasket for the intake and/or one of the screws that hold the throttle bracket to the drivers side of the intake.

__________________
James Zavesky
1987 300SDL
1991 500SL
1992 600SEL

I still have this car, among about 20 others and finally decided to address it.

Seems that the culprit is a bad wiring harness. The MAF on the passsenger side was bad and replacing the MAF and the harness that went to it seems to have eliminated the smoking.

Now I have a new problem.

The car won't accellerate past 20 mph most of the time and the ASR light comes on and the throttle is non-responsive when this occurs. No check engine light is on, just the ASR.

Bad accellerator microswitch? ETA's are new and so are the ETA controllers. Brake light switch?

Any insight is certainly appreciated.

Never mind.

After reviewing some threads...

My tires were overinflated (like 50 psi rear).

It was throwing the ASR for a serious loop.

Now I'm going to drive the car for an extended period to make sure the smoking is gone