Oil cooler hoses: Apply anything to threads?

[5cylinder]

I will soon be replacing the two oil cooler lines on my 1985 300CD-T (Calif.).

My question:
Should any kind of sealant or the like be used on the threads of the two new hoses?

I have consulted the Factory Service Manual, however, it does not discuss the oil cooler hoses, merely has an illustration of them.

Thanks for any help with my question.

[vstech]

I've never used anything on them. CLEAN is important. I suppose a light coating of loctite blue would prevent seizure in the future...

[charmalu]

I put a small amount of Anti Seiz on the threads. The Oil Cooler threads are aluminum, and the Cooler Line end is steel. Might help from the two dissimilar metals corroding together.

The threads is not what does the sealing, it is the ball/socket of the two fittings.

Charlie

[Junkman]

Examine the socket where the line connects to make sure that the fitting is not cracked. If cracked, it won't seal and you may spend time chasing speak unnecessary.

If cracked, replace cooler or buy a MBZ fitting that replaces the original fitting. Replacing may be cheaper if you buy the tap and drill.

[Diesel911]

X2 on the neversize

No sealing is done on the threads.

You need a backup wrench between the Hose Nut and the Oil Cooler or the Hose Nut and the Oil Filter Housing. On the Oil Filter Housing you need to thin the Wrench Head.

Plan an alternate Rid to Work or other important Places because there is a good possibility one or both of the Oil Cooler Nipples is going to strip.

I just did this between a week and 2 weeks ago and see the Pic for the results. Both Nipples were in similar shape.

There is some ways to try to avoid stripping the Nipples and there is a Nipple Repair procedure but it requires the correct Tap Drill, a Tap and the repair Nipples from Mercedes and a Hacksaw and a File. Meaning the repair is not going to get done fast.

[Diesel911]

If you happen to do the repair on the Oil Cooler and get Chips inside that you cannot get out but you don't have time to clean it out properly (as in My Case) only dirty Oil goes through the Oil Cooler.

Any thing that goes through the Oil Cooler has to go through the Oil Filter before it goes into the Engine. So the Nipple Repair is really safe to do.

In My case I got the Repair Nipples in slighly crooked. Insead of the Crush Washer that are going to work only if they seal on a Flat surface (I did not have any Crush Washers for the Job anyway) I coated the threads of the end of the Repair Nipple that screws into the Oil Cooler Housing with JB Weld.

Also the Repair Nipples are the same Nipples that are at the Bottom of the Oil Filter and infact the Nipples that I used came from Oil Filter Housings at the Junk Yard.

[5cylinder]

Thanks for all of the advice.

Incidentally, I replaced both oil cooler hoses on another 300CD some years ago and used aftermarket hoses. I thus found out the hard way about the criticality of the ball at the end of each hose being smooth and having no burs. After installing a new hose on the connection to the bottom of the cooler, I had a leak. The solution was to use some emery cloth to remove a small bur (that I *eventually* noticed) on the ball to eliminate the leak by creating a perfect fit.

This time around, I desired to use oil cooler hose replacements sourced from M-B. It turns out that M-B no longer sells them for this vehicle.

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Question: Am I flirting with disaster by using, say, 10 seconds or so of MAPP gas on the *hose* (not cooler) nut fittings at the cooler to help loosen them?

[Skid Row Joe]

Originally Posted by vstech

I've never used anything on them. CLEAN is important. I suppose a light coating of loctite blue would prevent seizure in the future...

Nor have I......

[Stretch]

X3 for copper ease

Dissimilar metal corrosion is what makes them buggers to remove

[DDAY]

I have had considerable experience with aluminum thread failures in non-automotive applications.

While aluminum corrosion can be a nasty problem, the problem is more often caused by over tightening during the initial assembly and "pulling" the aluminum threads by the stronger steel mating threads. A pulled thread is only revealed when dis-assembled and the aluminum thread material comes out with the mating steel fitting. No special removal technique will save an aluminum thread that was "pulled" at installation time. A "pulled" aluminum thread usually does not leak in service since the thread is not a sealing thread. It is only a mechanical joint holding the two mating parts together.

[winmutt]

Use a torque wrench.

[Diesel911]

The good news is the New Repair Nipples are Steel.
MB Part # Description 915013-013002 Screwed Nipples (That's what the label said.)
Or may be listed as N915013-013002

(There is a Letter in front of the Part Number but I did not record it for some reason) 007603-018101 Ring, General, Metal is the Crush Washer. Used if you think you can get the surface you cut with a Hack Saw filed Flat and the drilled Hole staright enough so that the Crush Washer can Seal.
Otherwise use some sort of Loctite or JB Weld on the threads and for sure it is not going to leak.

[redoubthill]

TEF-GEL.

Known from first hand experience in the marine environment for metals of different composition.

Not cheap, but you know what they say.......

[Diesel911]

I don't recall having any trouble using the dremel type tool on the oil cooler ends to cut the collars, but I was about 15 years younger when I did that.

I did loosen the lower hose brace clamp.

[tangofox007]

Originally Posted by winmutt

Use a torque wrench.

And the correct torque value is....?