My '76 W115 300D oil cooler had a nice drain plug on it. I only wish MB would have left that feature in.

I caution anyone who thinks of removing the lower oil line from the cooler to drain oil, if it hasn't been loosened before its quite possible that the aluminum threads on the cooler will have bonded to the steel nut on the line consequently when wrenching on it to loosen it you will wind up with no threads left on the fitting!
When changing oil cooler hoses I cut the old hose with a knife, take the cooler out and slit the nuts with a dremel tool then the nuts come right off without taking the threads with them.
And when installing new hoses I smear some Alunox in the threads, it helps to prevent dissimilar metals from siezing. Alunox is used on aluminum electrical connectors in industrial wiring, an electrician might even give you a glob of it enough for several fittings.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Yes--I had a 220D, W 115, that had a drain plug on the oil cooler.

Joe B.

That's how I would do it, the plug is easily accessible and a short oil pan should slide right under.

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1986 190D, 2.5L, 5-speed swap, 180,000 Miles (60K by me).
Jeep CJ-7 with Cummins 4BT/NV4500/AtlastII 4.3.
Grand Wagoneer 4BT project in progress!

I would not touch the oil cooler. Losening up 20 year old oil cooler fittings is just asking for trouble, now if you have a need for some new oil cooler parts go right ahead!


MB says somewhere in the 603's manual that the oil cooler does not need to be drained.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I agree, I've already trashed the upper threads on my cooler by over-tightening them. I have the original cooler and fairly new hoses. I was about 1000 miles from home when I noticed a very slight oil drip on the upper connection, and I couldn't leave it alone so I just had to tighten it "a little." Of course, I made it worse, and by the time I was done playing with it I had a major leak. I ended up sealing it with JB Weld and stopping the leak so I could get home. Now there is no way to remove the "good" hose from the cooler, so at some point I will have to replace the hose as well as the cooler.

Started my oil change on the SD today. Put my coffee can beneath the lower oil cooler line fitting and took a big crescent wrench and cracked it loose by one turn.

No problem.

Can't understand why you fellows have such a struggle with that fitting.

Tomorrow, I tighten it back up, put the drain plug back in, and fill it with Rotella Syn.

Took a sample for analysis as well. First sample since the head was replaced.

You have sounthern cars! You should have seen how fast the threads stripped on the SD's cooler. The top threads came right off with the fitting, no extra effort needed!


The oil on the SDL stays pretty much clear for 30-50 miles, so I must get quite a bit.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Used to do some version of most of the replies - then, I got a Topsider - have not done a MB oil change from underneath since then.

Far, far cleaner, and, don't have to removed the shield!

Oh yeah ... no laying down on the job!

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg

Sure, but, I also took a torch to those fittings before I replaced the hoses. I'd have stripped the lower fitting for sure without a good dose of heat.

Bet you didn't use heat on the SD...........did 'ya??

Brian,

I drain the oil cooler on my W116 the same way: turn the hose nut loose until it drips oil and then let it drain overnight. The oil that gets on the threads keeps them from fusing onto the oil cooler threads.

No problems so far, 275,000+ miles.

P E H

Of course you do.........where do you think I got that idea???..............

617's.....I change mine hot and don't jack it up. Pull the pan plug, then go up top and take the filter out and remove the fill cap. Give it a while [1/2 hour or so] then put it back together and refill.

Never would I touch my oil cooler lines. They don't leak now but if I touched them they would leak for sure!

The PO [and the original owner!] of my 240 told me he always ran a flushing oil for 50 or 100 miles before putting the "good" oil in it. Never done that either but sounds like a good idea.

You're a brave man Brian! The cost of an oil cooler keeps me from trying to get that last drop out.

Cheers,

Bill

On the L I did and both fittings took the threads off.

On the SD, the top fitting got a shot of PB Blaster the night before, and the day I planned on doing it. Put a wrench on it and it losened right up, I thought wow maybe this will be easy. The threads came off with the fitting with little effort.

I have had zero luck with oil coolers.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

After I have removed the filter from its housing, I use my rubber tipped air nozzle to blow a small amount of air into the top line coming into the housing. Go slow as it will slatter about if too much pressure is used. I am sure that this method is not as good as actually draining the cooler, but I would not mess with those fittings unless I had too.

As far as oil changing goes, I had a mercedes mechanic friend of my recommend a liquid dynamics P/N 24224T extractor to me a number of years ago. While it was darn expensive, I have used it more that I ever expected.

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Bill Brune

86 190D 2.5 5spd 314k
87 190DT 150k
87 300SDL 357k
95 E300D 115k
02 Jetta TDI 90k
99 Subaru Legacy

heh, what have we learned in the last 4 years... oil coolers are hard to work on...
for some.