HELP! Oil loss in 300E.

[Esquire]

I have a 1991 300E with about 129,000 miles on the clock. The car starts and runs flawlessly. Not a single puff of smoke from anything.

However, I have noticed that I am using up about a quart of oil about every month - about 1200 miles combined city/highway. The oil cap is tight, and the only leak I can find is a small oil one in the front of the engine just under the distributor cap area. I hear that this is a common place for this motor to leak. This car leaves no oil spots - but there is a bit of oil on the underplate.

Is the little leak the likely cause of the quart per month headache? One mechanic told me that he felt is was the valve seals which were leaking (but there is NO smoking - at ANY time) and possibly the head gasket was bad (the coolant is perfect, and NOT contaminated with oil). I ran screaming from his shop!

Actually, have any Mercedes bretheren had this problem before? Any ideas on what it might be or have a possible fix solution from the others? It seems like it may be expensive!

[Mike Murrell]

Your best bet will be to use the SEARCH facility here to get a better idea of what could be going on. I'll review some of what's been discussed at this site many times before.

Your car is a '91...not real sure if your model has the single cam(M103 motor) or the dual cam(M104).

The M103 motors are notorious for oil usage. In April of '89, MB supposedly began fitting the M103 motors with improved valve guides/seals. You mention seeing no smoke. Benzmac has mentioned that if the oil is getting by the exhaust seal/guide, you may not notice burning. Randy Durrance, another pro who used to respond here mentioned that M103 motors guise oil consumption fairly well.

I'd be inclined to agree. My 103 motor uses a qt. every 1200-1500 miles and my spark plugs are bone dry. No smoking whatsoever. I too have a little seepage from the U-shaped gasket at the front of the motor, but that would hardly account for the oil loss you and I experience.

From what I've read here and at one other MB web site, valve guides, valve seals, and leaking head gaskets seem to be to primary culprits.

[loubapache]

Esquire:

I have the exact same car and I experience the exact same thing (started about 3 kmi miles ago) and it has 98 kmi miles now.

Mike: The 1991 300E has the single cam (M103 motor).

Mine is also a bit wet around the front timing cover/head gasket area but there is no drop. Mine does have the belly pan so if there is a drip, I should see it on the garage floor.

I see higher oil consumption if I drive at high speed for hours. Normal city and occasional highway driving does not use oil.

Until July, 2001, I also owned a 1990 300E (same engine). Like the 91, that one has some wet area around the front timing cover/head gasket area but it drops one or two drops every day. When I sold that car with 120 kmi on it, it does not consume any oil.



Bo

[loubapache]

I should have said:

Mine does NOT have the belly pan.

Bo

1 quart in 1,200 miles is not terribly bad oil usage. The seeping from the upper valve cover is not uncommon.

I've had brand new cars over the years that used more than that when brand new and used the same amount over the entire life of the engine.

If it's not smoking, or puddling I would keep a quart or two of oil in the trunk and check at every fuel up.

Don't ever let anyone talk you into the idea that because it uses oil, the oil changes itself. If you do you will seal the engines fate by not changing it regularly.

Just keep the oil changed and between the marks and you will get many, many more miles from this engine.

Good luck,

[Zoni]

I also have a 1991 300E and had the same symptoms. Had the exhaust valve seals replaced and the problem has not reappeared for 40K miles (now have 157K). When I had it done by independent it was approximately $200. Very surprisingly cheap for a Mercedes repair.

[Esquire]

I agree. $200 dollars is surprisingly cheap for ANY Mercedes repair short of an alignment. I hope it was an honest job.


Congradulations!