Nice work, thanks for posting the pics.

Well I got this buttoned up today. New radiator, this used oil cooler, my cooler lines, new belts, hoses, clamps, coolant thermostat, water pump, other odds & ends. Water pump failed immediately, leaking from the top weep hole, took it for a drive, it only got worse. Gates brand pump. Off to local parts house for a replacement. Seems OK now.

Took the car for a nice drive up and back to meet friends for drinks & dinner. Drove great, I can tell the oil thermostat is not stuck open, oil pressure comes down a bit at idle, just over 2 bars, it used to stay pegged all the time. Haven't caught that thermostat opening yet, both pipes have stayed cool. It's also cool here (actually warm for February), about 45-50°F today.

I've got CRC Thermocure in there now to flush out the well documented rusty block issues these can suffer from. This has to be the 6th time I've flushed this thing, tried all the posted tricks and then some. Gets better each time. I think this Thermocure will solve it. Going back in with Zerex G05 & deionized water 50/50 when its all said & done.

ThermoCure is very effective, be patient and let it work BUT protect the block from freezing while using it. Great product.

I used the same MasterCool AC ferrule crimper when I re-hosed the oil cooler lines on my 1984 300D. I used AC barrier hose, which is rated for hot oil and much higher pressure. No leaks in ~5 years. The OE hose had been hacksawed by the p.s. belt, due to sagged motor mounts. I cut the new upper hose 1" longer to better clear that belt. Amazing M-B never thought of that.

I'm surprised that a 240D even needs an external oil cooler since even classic V-8 U.S. engines don't. I assumed it was needed for the turbo engines since they have oil squirter coolers under the pistons. My 2002 Chrysler 3.8L minivan has an oil cooler, a simple pancake between filter and block which routes thru engine coolant, so your first idea of using the radiator transmission cooler "should work". Ours has the factory tow-package and AWD, which adds that oil cooler and p.s. cooler.

Agreed. Car is in heated garage, no worries on freezing. Planning on running errands through the weekend, then the flush and G05 fill.
This car suffered similarly, old hose wounded by p/s belt due to mounts. Mounts were relatively new when I got it, but historical documents show me replacements point-in-time. I'm surprised this needed the cooler too, and more so with this latest service part oil t-stat, slightly higher temps. I guess hot climates might have needed it, so the a/c combo plus homologating to the US market that has hot zones made their decision for them. As far as classic V-8s go, Caddy HT4100 and Olds Diesels had oil coolers on them. I've got a few Olds diesel powered land barges.

I also did a vacuum pump while I was in that far, found a NORS model made by same mfr of OE, felt nice and solid. The holy trinity of catastrophes now averted for the time-being, reinforced rad upper inlet, oil cooler hoses, and vacuum pump all fresh. Someone had already done the front seal, didn't realize that until I popped the damper off, did it anyway, along with that bastard of a seal race. Timing chain is nice and tight. Oil changes beyond counting in the records I have going back to day 1 on this car. Crankcase is pristine. Coolant...not so much.

probably already mentioned but…
a heat exchanger in lieu of the cooler
The transmission cooler on a radiator for A/Ts

Good you finally found a good Oil Cooler.

Here is a good thread of fixing the OC nipples when stripped off, from 11 years back.
Couple links in there also to click on.

https://www.peachparts.com/shopforum/diesel-discussion/333912-oil-cooler-nipple-fitting-weld.html


Charlie