Oil Coolers - To Drain, Or Not To Drain:
 

I have no drain plug on the oil cooler on my W116. I used to unbolt the lower hose and drain it, but quit because it was such a PITA.

What's the forum's consensus on draining it??? Seems to me that if you do drain it, you would have to block the airflow through the radiator to get the motor hot enough for it to open and fill.

My car never gets over 185°/190°F...ever, so I am curious to see what others are doing....Robert

This has been kicked around over the years through a bunch of threads. I did a google search, "draining the oil cooler" and a bunch of stuff came up. seems most say it is not necessary, don`t get that much oil out, will strip the threads etc....... some good reading.

Here is one.
http://www.peachparts.com/shopforum/showthread.php?t=293337

I did discover the old 220 Diesels had a oil cooler drain, then eliminated when the W123 replaced it.

Charlie

Here's my plan
 

I only recently became aware of this issue, but here's what I'm planning to do on my 240D: there are two 10mm small bolts that hold the oil cooler to the radiator. If I undo those two bolts I can leave the hoses connected, yet still move the cooler rearward around the power steering pump. This give me enough slack to raise the cooler up by a couple of inches. I'm hoping that this will elevate the cooler enough to cause the oil to flow down to the filter housing.

After all the trouble I've had with oil cooler hose leaks there is no way I'm gonna mess with loosening and tightening them again.

Kurt

In your case you already know you can remove your lower Oil Cooler Hose without stripping the Threads off of the Aluminum Nipple on the Oil Cooler. So you have no risk of that happening to you.

For others they need to be aware that there is a risk of stripping the threads on the Oil Cooler Nipples (this happenedd to me with the upper Oil Cooler Nipple; I never removed the Lower one so I do not know if it would also stripped or not) when the remove the Hoses.
Some other method like driving your Car up on Ramps to drain the Oil Cooler is safer.

I don't bother; I figure the old oil in the cooler will be diluted by the two gallons of fresh oil I just dumped in. Plus there's also oil trapped in the head, etc. that you can't do anything about anyway.

But then, I also run dino oil, so what do I know? ;)

The oil cooler will fill with oil after you start the engine. Hot or cold.

Also Oil trapped in the Fuel Injection Pump.
If you read the Technical Data Passenger Cars Book they have a spec for a Dry fist filling of Oil in the Engine and a spec for refill after an Oil Change. There is 1 liter of Oil trapped somewhere.

heh, I figured a poll added would make life easier in the future on this question...

Thanks for the input.....