I have owned a 89 300se for about a year. The car has never overheated or ran the slightest bit hot. I replaced the radiator and fans about 11 months ago, (I hit a deer not due to high temp).
In the past week I noticed I was using a quart of oil in 500 miles. It has always had a slight leak from the front seal. But this was more like a quart every 2k. I checked the coolant and found the mayonaise looking stuff in there drained it and flushed it, but after another 400 miles it is back.
There is no water in the oil, plugs look absolutely perfect, no smoke or steam at the exhaust. But on the back of the engine passenger side oil is leaking down onto the trans.
I have never had a head gasket fail so I am not sure how oil would get in the water but not vice versa. Also what would cause the gasket to fail? Did replacing the cooling components increase the pressure enough to blow the gasket? When I searched this it seems to have happened when the system was weak but my cooling system was fine before.
I drive the car 1k a week and it has 254k on it.
Thanks for any insight into this.

It's the head gasket. Near #5 cylinder there is a water passage in very close proximity to an oil passage. Since the oil pressure is higher than the water pressure, the oil will get into the cooling system.

Thanks for the reply.
Man that sucks, if I had any indication that something was wrong and I let it slide I could expect that, but I guess with this kind of mileage things are going to happen.

__________________
“Fundamentally, sustainable development is a notion of discipline. It means humanity must ensure that meeting present needs does not compromise the ability of future generations to meet their needs.”--- Gro Harlem Brundtland


1989 300se 250,000
1983 BMW 528e 100,000
1999 Olds Alero 80,000

These pretzels are making me thirsty.

Is there a "average" mileage that the head gaskets seem to go on the 3.0L I-6's? I am wondering, because I am considering a 91 300SE with 181K.

Thanks.

I'm at 200,000 and mine has never blown. More m103 people, please post.

It sounds like a leaking valve cover gasket, not a cylinder head gasket.

Clean the engine and look for fresh oil leaks.

I have a 1991 300e with over 245k miles and it continues to perform well, uses 1 qt every 3,000 to 3,500 miles now that I relaced the leaking upper timing chain cover gasket.

Don't rush into fixing something that isn't broken. Determine where the oil is going.

What weight oil do you use?

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

HIs coolant had oil in it. The headgasket is bad and needs to old R&R. I suspect I'll have to do this on mine.

__________________
Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

In checking different sources and especially this forum, I found that it is a common problem for these motors. But not a hard fix. My car has 250,000 miles on it, and I drive 200 miles a day.
Of course I say it is an easy fix, but I have six head bolts that will not come out and now I have stripped them and ruined two ratchets. I think that the PO has used loctite on them so I may have to have it towed today.
But I consider the bottom end of the engine to be bullet proof and the gasket will last probably 100,000 and from what I have read the new gasket is a better design, maybe longer.
Beats driving a Taurus.

__________________
“Fundamentally, sustainable development is a notion of discipline. It means humanity must ensure that meeting present needs does not compromise the ability of future generations to meet their needs.”--- Gro Harlem Brundtland


1989 300se 250,000
1983 BMW 528e 100,000
1999 Olds Alero 80,000

These pretzels are making me thirsty.

I am TOTALLY impressed that there are people here who can diagnose an engine without even seeing it or at least reading the compression test/leak down test results.

There are several things that can be causing this, but the head gasket is not a common problem on the 103 engine. It's close cousin, the 104 engine does indeed commonly exhibit head gasket problems, but it is much more infrequent on the 103.

Unfortunately most everything that could cause these symptoms require head removal, but putting a head gasket on and putting the head back in place without thoroughly testing the head would be a BIG mistake. To begin with, at this mileage it would be foolish to put the head back in place without doing a valve job including new guides and seals. Secondly, these heads can corrode between combustion chamber and water jacket causing the indicated symptoms.

R&Ring the head on one of these engines is a very advanced DIY project. Even if done by a pro, it would best be done by a pro with experience on this engine, or at least one of its cousins.

Best of luck,

Oil was leaking down the rear passenger side onto the trans. Cleaned the engine and saw the head itself was dry but the block soaked with oil.

I would'nt just r&r the gasket but will have it checked out by the machine shop, If I can get it off, just talked to the shop and they don't want to touch it. Mention Mercedes around here and they usually see dollar signs, I was surprised.

What is anyones opinion about using a large ez-out or equivalent in the stripped out bolt head? Am I just asking for trouble?

__________________
“Fundamentally, sustainable development is a notion of discipline. It means humanity must ensure that meeting present needs does not compromise the ability of future generations to meet their needs.”--- Gro Harlem Brundtland


1989 300se 250,000
1983 BMW 528e 100,000
1999 Olds Alero 80,000

These pretzels are making me thirsty.