OK, I have a 1978 300D, and I FINALLY got the transmission and radiator fixed, rotors replaced, and new tie rod end. I got a "clean bill of health" for general purposes, it seems. There is about 180k miles on the car. It also does not smoke (black or white).

But the oil is very dirty, which surprises me. Does oil often get black with very little driving (this car hasn't seen much pavement since last December; maybe 1500 miles since the oil was last changed)? The oil level dropped some, too. It makes me wonder if there is a silent problem with the engine, or if there is a small adjustment (such as, the idle is too rich and causing extra deposits?), or if this is within the "normal" range? I've searched all over online to learn about this but it's been hard to really find what I need.

My car also diesels for a few seconds after I switch it off. It doesn't do it constantly, so I was not concerned--until reading about it online. (I have to use a mityvac and figure out where the air leak is, figuring that is the most likely culprit.) But then I keep reading about "manual shut off levers" which are to help against run away engines. I can't find my manual, and I am wondering WHERE the thing is located. Is that different from the idle lever on the dash? How does it operate? I just want to always be prepared for worst-case scenarios. I hope I'm not coming across as pessimistic...

Thanks SO much for any light you can shed here... any links... anything.



bebu

Black oil is 100% normal. It's said that the only time the oil will truly be clean is the time it's flowing between the bottle and the valve cover.

Your shut-off problem may be caused by weak vacuum or a leaking diaphragm. Search around the forum and you will find lots of information about how to search for your exact problem.

"Dirty" oil is very normal for these engines, the oil will turn black almost immediately, it's nothing to worry about.

Regarding the failure to shut off, you are probably correct to suspect a vacuum leak. The manual shut-off lever is located on the engine (left side, on the "throttle" linkage). It is a metal lever with the word stop on it.

BTW, a runaway engine is not the same thing as a failure to shut off. A runaway engine is a malfunction that causes the engine to go to maximum rpm.

THANKS guys, for your help!! I mean that!!

Re the oil... if jet black oil is "normal" then how in the world does a person know if the oil is truly dirty? Is it gritty? Smelly? I could always tell what dirty oil was with my other cars, but the oil for Mercedes diesels must be different I guess...

THANKS Craig, about the manual shut off info. I will look for it just to know where it is.

It sounds safe to venture forth in the car, after all!

bebu

not just mercedes diesels all diesels will have black oil just change it at regular intervals

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commercial fisherman diesel in my blood in my boats trucks and Dear old Dad has had me drivin them since i got my first license in 1968
1986 300 SDL 427654
1999 Chevy Crew Cab Dually 225423
1986 300 SDL 287000 Dad's
1987 190 Turbo 158000 Mom's (my inheritance)

There is no way to tell just by looking at it unless there are solid chunks in the oil, at which point you have other things to worry about!

You can change it at intervals or you can extend the intervals by sending samples to an oil analysis lab and let them tell you when it's time to change it based on the oils contents.

Here's a picture of the driver's side of my engine (ignore the circles). Right next to the valve cover (about halfway up), there's a little red 'Stop' square. That's the shut off.

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1984 300TD

If your car has a manual idle adjustment control in the cab, it may help to turn the idle speed down to the lowest speed before using the manual stop lever on the engine. My '80 300 TD manual shutoff won't stop the engine unless the idle is turned all the way down. It just acts like it's being slowly strangled. Steve