so the other day before my usual "pre drive" inspection on my 1991 300se .. i loooked in my radiator expansion tank and much to my dismay i found a slight layer of oil in the tank. I checked the oil - no coolant apparent in the oil (its not milky). Oil does leak .. it looks like the back end of the engine.. i haven't exactly found the "leak" yet.. but i am thinkin it is the head gasket. It could be the valve cover gasket too.. I need to take a closer look. I was reading some where that some how oil got into the coolant by other means besides a leaky head gasket (something like a clogged radator would create a vaccum and suck in oil and exhaust air from the the oil cooler, which doesn't make any sense to me because i see no connection between the two.) I am an airplane mechanic so I know how to wrench.. but really have never worked a major job on a car, I am pretty sure I can do a head gasket job myself, save me $1400... the car has lots of room and a straight forward engine.. thats why i bought it, ive only owned it for a month tho.. and am kind of mad that i have to do such a repair right away.. it has 127000 on it. When I bought it, it had a slight oil leak.. figured it was the valve cover gasket.. guess I should of spent $150 on a pre inspection before purchasing it. Thats what I get!! What are your thoughts about oil in the coolant.

 

Check the head gasket.

 

i agree headgasket.

 

WAIT BEFORE YOU REPLACE THAT HEADGASKET. there is whats called a oil to coolant exchanger on your car its located on the side of your oil filter housing this is a small radiator that cools the oil in your car and there is a service information out like 10 years ago that says check this item first and believe it or not they leak internally all the time. i saw one last month. we actually replaced both the head gasket and the exchanger but if your looking to save money replace the exchanger first and see if the oil in the coolant keeps happening.

 

sounds like a deal to me, might as well replace the littler stuff first, what does the oil to coolant exchanger exactly do.. its like a mini oil cooler? I see there is no oil cooler by the radaiator so that ditches the idea of having that copper peicing between the radiator and oil cooler go bad. I remeber that happend on an old pick of my dads. Know of any place where I can find some service information in trouble shooting this problem? I orderd the benz manual on ebay.. a factory copy, doesn't provide much information- all the good diagrams dont cover the 300se model.

 

I couldn't find the exchanger hmm.. i'll keep looking, is it possible that it isn't oil at all.. and its tranny fluid? I warmed it up and I see I am low on tranny fluid.. could something rupture in the radiator to cause the ATF to get into the coolant?

 

if M104, heat exchanger.

 

Hello golfpropilot,

yes, as Alfonso already wrote, M103 has got a ATF/water heat exchanger.
ItĀ“s component of the radiatorĀ“ss right side - there You can see the attached ATF-lines...

Greetings
Peter

 

hmm.. i wish cars were easy to diagnose like airplanes.. guess im not use to working on cars so its different, same concepts tho - wish the documentation was better.. airplane maintence diagrams are quite extensive.. the MB program is probably just a general guide

 

if you determine that it isn't tranny fluid and is in fact, oil, than of course it is the head gasket. A good friend of mine gave me her 190E 2.6 because of this very problem. the 2.6 is basically the same as your 3.0 except shorter stroke. The head gasket was also leaky in the back. The job actually wasn't too hard to do. The Manual says you must remove the intake manifold but this is not the case. the only special tools i needed was a 12 pt star for the head bolts and an exceptionally large alan wrench for the timing chain tensioner (if you are up to the job yourself). If not, buy discount parts online and take your car to a trustworthy foreign auto mechanic and tell him what you want. While the head is off it is essential that it be reconditioned at a repudible machine shop because the valve guides in these engines aren't that great. Another tip; don't let the machine shop buy the parts for the rebuild, order them online also, they are usually 50-60 percent of the regular retail.

I've been down this road, hope this helps!



[IMG]local://upfiles/14165/5BCD7682689A4417AB26EFA3A525D162.jpg[/IMG]

[IMG]local://upfiles/14165/40D9B508B3DB4FF780DC0C14B1AD8BBB.jpg[/IMG]

[IMG]local://upfiles/14165/02103D7ED49E4384A094C8C6122BD54C.jpg[/IMG]