There's not much info here on the forum when it comes to the coolant - cooled oil cooler on the 1995 E300 so I thought I'd share my recent experience with one.

I just recently purchased a very nice, high mileage 1995 E300. It had been run hot AFTER the previous owner had begun noticing black oil in the coolant. I paid $750 for the car and drove it 52 miles to my house without any issues. It did seem to get a little warmer as I found myself in stop and go traffic after exiting the interstate. I had no previous experience with the OM606 and I was unaware of the coolant - cooled oil cooler on this particular model so knowing it had been run hot and there was oil in the coolant I just went ahead and removed the head. I didn't do any extensive testing. I was looking forward to the learning experience on a new engine model and I didn't need the car, I just bought it to play with. After putting a straightedge to the head I determined that the head was actually warped but not beyond repair.

A few days after I got the car torn apart someone from the forum gave me another 1995 E300 that they had stripped of everything except the running engine and transmission. I decided I'd just use the head from this engine and be on my way. That's what I did. There was some pitting around a few water jackets but it wasn't anything that would create a problem so I installed a new head gasket and the donor head. The car went back together beautifully. I replaced the faulty glow plugs while the head was out and the car would start and run flawlessly. I de-oiled the system thoroughly and put in Zerex G-05 coolant. For the next 150 miles it was pure joy.

I bought a new radiator cap from the dealer and also bought all new fuel lines. When I went to put the new cap on I noticed that the system wasn't pressurized. When I looked into the expansion tank I saw black oil. It was NOT residue from a shoddy de-oiling. I disconnected every line possible and also the block drain when I de-oiled it. I backflushed, forward flushed and every kind of flush I could do to remove the oil. I used dawn dish detergent to emulsify the oil and when I was finished flushing you couldn't find one oil droplet or soap bubble coming out of the engine. I was disappointed. Somehow my new head gasket and head just weren't up to par. The car ran perfectly. No smoke. No missing. Perfect Temps.

I drove the car home and began dismantling the engine. I was going to just go ahead and have the head tested. I had thought it COULD be the oil cooler. I knew the oil pressure was greater than the coolant pressure but I thought surely after the engine was shut down then the coolant would work it's way into the oil but it never did so I thought the cooler was fine.

I'll wrap this story up...I removed the head again and had a compete valve job done and the shop cleaned up the mating surface although the head tested very well. While the head was in the shop I rigged up a way to test the cooler for an internal breach and guess what?........the cooler was breached. Live and learn. Trutfully, I have enjoyed every minute of working on this car and my confidence is going to be high for this car now that the head has been worked over. I removed the oil cooler from the donor car and tested it. No breach! If all goes well I will have the car back together by week's end.



Let my learning experience be a source of education for you if you have a 1995 E300 and you find black oil in your coolant but no coolant in your oil. Check your oil cooler.

It could be worse. I could still own a Ford.

An interesting and well-told tale and a lesson for all of us in being careful with assumptions. I've had my coolant-to-oil heat exchanger resealed because it was oozing oil but have not yet found oil in the coolant or vice-versa. BTW, the 1996-97 E300s also have a heat exchanger but on the left side of the engine near the oil filter canister.

Incidentally, does your monovalve leak?

Jeremy

I haven't noticed any leakage from the monovalve.

With W210 and W202 OM605/6 powered vehicles in the UK, it is the ATF heat exchanger in the left hand (looking at engine bay) header tank of the radiator which leaks water into the ATF circuit on the auto models (722.6) and really turns it all to poo.