I've been told I have one. Does anyone know how hard they are to replace? Could it be an "O" ring? Its leaking at the fitting and I'm wondering if I can just clean it out and replace an O ring if it has one.

What model/year of vehicle are we talking about?

In most cases the line has to be replaced. Is it leaking at the threads or the compression fitting? If at the fitting, it needs to be replaced ASAP to prevent a catastrophic failure from sudden oil loss.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Assuming that the vehicle in question is the '82 300SD listed in your profile, there are no o-rings. Is the fitting tight? Which end is leaking?

Yes, its my 300SD, its the bottom fitting on the oil cooler. I assume the shop tried to tighten it, they are very good and they fixed some of the other leaks.

The risk is that over-tightening the fitting can strip the threads on the oil cooler, which is fairly expensive to replace. What does the shop recommend?

Their advice was "to fix the leak" and that's it. I'm wondering if I should just go ahead and replace it.

Just a thought, could I use high temp thread tape (PFTE) on the threads?

Not likely to work, but, you surely could try it.

Depending on whether you can easily remove the fitting, you could polish the taper on the oil cooler in the hope of getting a better seat. You'd need to use a very fine emery paper. You can also take a look inside the taper on the end of the attachment tube. Again, any abrasions here will result in a leak.

I've successfully cured a leak in the brake lines using this method.

One warning: If the fitting to the cooler has been in place for 20 years, it's a slow and tedius process to remove it without damaging the cooler. If you simply add wrench and apply torque, you'll surely strip the aluminum threads on the cooler and then you'll be in worse hurt than you would otherwise have been with the leak.

You need a lot of patience, some PB Blaster, and a bit of heat on the nut to be successful. The nut must be moved repeately back and forth without too much forcing to prevent wiping out the threads.

I wouldn't disturb that line to much. After 20 years espeicaly if you are up north those crimps get a bit rusty. They don't like to move. If you pull it apart be ready to replace it if you have to. If you plan on keeping the car you should anyway.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I just replaced my lower oil cooler fitting with the "screwed nipple" (see post #10 in
the thread "Oil Cooler Hose Source" started by tangofox007).

Oil Cooler Hose Source

I had a leak at
the threads and when I examined the fitting, there were dents in the sealing surface.
Total cost of repair $25.

Will be buttoning it back up this weekend and we'll see how it fares.

Based on this thread, I should be able to replace the lines (at least the bottom one) and change the nipple without replacing the cooler. That is assuming that the problem is not in the cooler itself.

The original nipples are part of the cooler, they are talking about having the cooler machined to install new nipples. I have a similar problem with my top connection, the threads are now partially striped. Replacing the nipples may be cheaper, but I think I'm going to bite the bullet and replace the entire cooler:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41U41AVWRF&year=1982&make=MB&model=300-DT-001&category=All&part=Oil+Cooler

I'm just not interested in adding any more mechanical connections to the oil system.

If you guys are talking about the black painted type oil cooler that has one fitting up top and the other on the bottom for a 617 engine, I have one leftover with both lines in very good shape, from the engine I swapped into my 240, I re-used my original 240 cooler as it would fit to the mounts on my radiator (older style aluminum with both fittings on bottom).

Give me something for it and cover shipping and it's yours.
-Chris

Craig will take it..........

I'll give dmtinker first refusal, he's in a more urgent situation at the moment. If he doesn't want/need it, I'd be glad to take it off your hands.