I've read this thread with interest and appreciation of the combined expertise available here. Does my 1985 300D (617.952 engine) have a combined engine-transmission cooler like the 1983 300SD in the thread? It looks to me like my transmission has a separate cooler, mounted just to the left (driver's side) of the engine's radiator. The two appear to be a single manufactured unit but as separate components. How would one leak into the other?

Jeremy in Santa Rosa, California

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Your transmission cooler is identical to the 300SD. It's in the lower section of the radiator. The separate cooler that you refer to is the engine oil cooler. There is no possibility of the engine oil cooler leaking into the radiator. The lines to and from the cooler do all of the leaking necessary..........

Bad news I finially put about 100 miles on the car and I could see just barely see some cloudness in the trans fluid. Not pink milk like before, but not transparent red. It had a very very slight cloudiness to it. I could not notice it on the dipstick, but had drained some from the pan into a clear glass jar and that's when I noticed it. So due to my paranoia of the aluminum radiator I got from reading some of the replys here I cut the rubber trans connecting lines and now have bypassed the radiator completly and added a trans oil cooler that now sits up front behind the bumper.

I will follow up again after some more miles. Geese, I hope its fixed. Regardless, many thanks to all of you.

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1982 240D 370,000 daily driver, great car!
1983 300SD
1995 350SD gone to rod bending heaven.
1986 300SDL should have never sold it.
1995 2Dr 4x4 Tahoe with a highly modified 6.5 turbo diesel, 6in lift.

Actually the tube that runs inside the radiator that carries the trans fluid is copper. That probably was the problem all along.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I found how the water was getting into the Trans. I believe. The Trans dipstick tube had a good size gouge in the side on the tube, about 1.5 inch long. When hosing off the engine or driving in the rain, water would have entered. Bad thing is it was most likely letting in more than just water. Road debris ect. Soldered it closed and took it to a shop to flush the trans. I haven't lost any radiator fluid from the now open trans tank on the radiator so I think it was ok, but I will still leave the aux trans cooler on since it's mounted already.

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1982 240D 370,000 daily driver, great car!
1983 300SD
1995 350SD gone to rod bending heaven.
1986 300SDL should have never sold it.
1995 2Dr 4x4 Tahoe with a highly modified 6.5 turbo diesel, 6in lift.