My 1987 300E quit on me just as I was approaching our driveway. It suddenly started losing power and then stopped running.

I did some preliminary cheking and found that there is a thick layer of black oil at least an inch deep inside the expansion tank of the cooling system.

I pulled all 6 plugs and they are uniformly the same... yet odd in that each plug looks like the dark and light side of the moon. One side of the plugs are black and the opposite side white.

I tried to restart the engine and it kind of belched white smoke out of the air breather. At another time it seemed to sputter on about two cylinders.

I suspect a blown head gasget but there is no reason that I am aware of that could have caused the gasget to blow.

There appears to be no water in the oil. The crank oil appears normal and very clean while the oil in the expansion tank is thick and black.

Any insights will be greatly appriciated. I've only been operating the car for a few months so I don't know it's history. It has about 230,000 miles on it.

Smiles.

Head gasket time, Earl.
Gilly

Thanks for the reply Gilly. Do you know why the oil in the expansion tank is so thick and black rather than light and clean like the oil in the crank case?

Also any idea what the average cost is to replace head gasget in the 300E? (private shop not dealer)

Earl:
No, not any idea at the moment. Maybe exposure to compression gases? "What else could it be!"
I think it runs around 8 to 10 hours of labor. Make sure the head is checked for warpage.
Gilly

This is the first time that I've seen a head gasget blow for no apparent reason. Is there something peculiar to the 300E 6 cylinder that explains why the gasket blew?

Earl:
Nope, no explaination has ever been offered to me, but this certainly isn't the first I've heard of it. The quote that TKAMIYA gave would be a 104 engine, not a 103. A 103 should be less.
It's almost common enough on 103 and 104 engines that you can almost catagorize these engines into 2 basic groups, those that have blown headgaskets already and those that will shortly.
Gilly

The head gasket material...
 

... OEM was defective, but Mercedes will never admit to it. This is a very common problem on 124's, including mine, which I have yet to repair.

They now use some super high tech space age sealant to seal the head onto the block.

Other reasons mentioned for this failure rate is an aluminum head attached to a steel block, which was a poor design I suppose.

Be sure to have your valves done "while you're in there", so you won't have to revisit the process of taking off the head at a later date for valve problems.

Good luck

~Paul

Thanks Gilly. Is there anything you might recommend doing while I have the head off... like rings or bearings? (230,000 miles)

Paul,

What do you mean by OEM?

The original gasket that came with the car (original equipment manufacturer).

Also, if you take out your expansion tank and dump all that gunk out, then refill with coolant/water, run the car for awhile, the sludge will keep rising to the top of the expansion tank.

Rinse and repeat until you get almost all of it out ...

That is, if you can't bring it in for immediate service.

Good luck

~Paul

Earl:
OEM is original equipment manufacturer, term gets referred to quite a bit.
Sorry to say, and no offense intended, but the headgasket is the same, has not changed. It could be due to the aluminum head, but again, no official explainantion has been offered to me. If the explaination for somehting like this isn't on the pretty stationary with the star in the corner, or told to me by a guy with a white lab coat on, I don't take alot of stock in it. I believe what paul is referring to is the modular vee engines use a sealant on the headgasket.
As far as doing other work on the engine, it's more of a personal decision on going ahead and replacing rings and bearings and so forth. I recommend basing the decision on what your plans are for the car. If you'd like to drive it say another 100,000 miles, the engine should handle that OK, just do what is needed. If you'd like to drive the car "indefinitely", then maybe you could look at just putting in a MB (or other, such as Metric) reman engine in it. Usually, of course, the reman route is for blown engines, not a blown headgasket car, so this would be a little extreme, in my book, but thought I'd throw it out there anyways. I don't really favor the "middle of the road" approach of just trying to fo rings and main/conrod bearings and so forth in the field. To do a good job it really should be done by a specialist to get a good job done. By the time you get done screwing around with all that, your money ahead to get a reman engine, plus if you get an MB reman the warranty is pretty good, too, 3 years I think it is. Well, dwell on that for awhile, anyways. i recommend making sure the cooling system gets flushed out a number of times. One recommendation I heard is to use marine bilge cleaner and water to do the initial flush to help get oil out od the cooling system. You could consider getting the radiator cleaned seperately at a radiator shop also. If the work is done soon, you shouldn't need to worry about the hoses on the car, extended periods of operation will lead to hose failures. I also recommend a new pressure tank( the one coolant is added to), plus there is an expansion tank in the right fender that you can't see that should be replaced also, as it will hold oily gunk in it and eventually be intro'd to the cooling system later...
Gilly

Ok Paul and Gilly...

I think it best to just replace the gasget for now. The engine appears to be in good shape other than this unexpected problem.