How do I repair oil cooler fitting

[Jim Condax]

I’ve replaced both oil cooler hoses on my 1985 300SD and am in the process of reconnecting them to the oil cooler and filter housing. All but the bottom cooler fitting went on fine. Unfortunately, the bottom fitting is damaged and needs to be repaired. I believe the threads measure 22x1.5mm but I’m not sure. Can I use a standard rethreading hex die for this purpose or does this fitting have a special thread? Anything else I should know before trying this repair?
Thanks,
Jim

[vstech]

If damage happened. There won't be anything to rethread. What happens is the aluminum fitting bonds to the steel nut and when you loosen the nut the threads rip off. You need either a new cooler or a replacement fitting installed. .. sorry.

[otto huber]

I have a used oil cooler that I could sell you. Let me know if you're interested and I'll check the part # . It came off of a 1981 300SD.

[Diesel911]

Originally Posted by Jim Condax

I’ve replaced both oil cooler hoses on my 1985 300SD and am in the process of reconnecting them to the oil cooler and filter housing. All but the bottom cooler fitting went on fine. Unfortunately, the bottom fitting is damaged and needs to be repaired. I believe the threads measure 22x1.5mm but I’m not sure. Can I use a standard rethreading hex die for this purpose or does this fitting have a special thread? Anything else I should know before trying this repair?
Thanks,
Jim

You can buy the Fittings that go on the Bottom of the Oil Filter Housing from Merceds (they were about $11 each) and a new crush washer.
MB Part # Description 915013-013002 Screwed Nipples (That's what the label said.) or Or may be listed as N915013-013002
If you don't want to pay the full price for a new Nipple you can pull them from an Oil Filter Housing at the Junk Yard.

The Crush Washer is 007603-018101 Ring, General, Metal"

That same Fitting is used to repair the Oil Cooler Nipple if the Nipple threads are stripped.

I have done this repair on My W123 Oil Cooler. You cut the Threaded end off of the Oil Cooler, drill a larger hole, Tap the hole an screw the new Nipple in place. You are supposed to use the Crush Washer between the Oil Cooler and the Nipple but if the hole is not straight the Washer is not going to seal.
That happend to me and I did not use the Crush Washer I simply coated the Nipple Threads with JB Weld and let the Epoxy do the sealing.
Loctite I think would also work if you degrease the inside and outside threads with Brake Cleaner.
Also note that the Oil that goes through the Oil Cooler is dirty Oil that passes through the Oil Filter on down the line. That means if there is a few stray chips inside the Oil Cooler after drilling the chips are not going to get inside of the Engine because the Oil filter is going to stop them.

There is 2 really good threads on the repair but it might be listed as a repair on a W123. The Threads list the Drill size the Tap Size and proceedure.
Repair Links
Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

Note that Sears Sells an Irwin tap in the correct size at a reasonable cost. The bugger is the reduced shank size drill (you will need a 3/8 Drill Motor that turns somwhat slow) which cost a lot at Sears or other hardware store.
I got mine on eBay and was around $7 + shipping but I had to wait for it to arrive.

[Diesel911]

I never answered the question about rethreading the Oil Cooler external threads are 22x1.5 and you can use a Hex Die and eBay Sells them. If the eBay Seller is mailing it from China it will be cheaper but takes about 2 weeks from time of purchase.
I don't know if there is room to fit one one while the cooler is in the Car because the die is like 2" wide acrossed the Flats.

Also it is going to depend on how may good threads you have left and are willing to risk.

When I stripped the top Nipple I had no Die but only the last 2 threads were stripped. When I screwd the Hose end back on I degreased the Threads and coated the Nipple Threads with JB Weld. And I had no issues with that for 6 years.
In the time between the 6 Years I bought the Drill, Tap and repair Nipples to fix the Oil Cooler properly later and that is what I did.

If you get a used Oil Cooler or repair the one that you have put some Never sieze type compound or Grease on the Nipple Threads so they don't rust or corrode again.

They do have Metric Thread Files and 1.5 is a common Metric thread Pitch. I have 2 for US type thread but I never liked using them. I have also filed threads with a Jewlers File or other small File like a Triangle File but it is time consuming and with any of the above the Oil Cooler needs to come out.
The Good News is the Oil Cooler Hoses don't seal on the threads.

[Diesel911]

How is the job going?

[Jim Condax]

Diesel 911, update on my lack of progress.

Purchased a 22x1.5mm thread chaser die and cleaned threads on lower oil cooler fitting. Lower cooling hose will still not thread on cooler fitting. As a test, upper hose threads on both upper and lower cooler fittings by finger all the way. To me, this means the lower cooling fitting is fine and that the problem is with the fitting on the lower hose. The fitting at the other end of the lower hose fits perfectly by hand at the filter housing. I don’t know how I could have damaged the lower oil line since I used no wrench and had previously tightened all of the other three fittings by hand.
Rather than risk damaging the oil cooler fittings I’m going to buy another lower hose ($50 vs. $350) and be very careful how I screw it on. Another week of waiting for parts.
Thanks for your confirmation on the thread size and your suggestions.

Jim

[Junkman]

I went thru the process of installing the nipple. My first choice would be to find a good cooler. The required tap and drill plus waiting on the nipple make the cooler route economic and convenient.

What happens is a gorilla over tightens the line nut causing a hairline crack which results in a leak. You will need a drill press to get a straight hole. Unfortunately metal thieves made off with my press.

[TnBob]

Once again... from vstech.. who has forgotten more than many of will ever learn about MB's :

Most members here appreciate it IF you actually read responses to your query.

"If damage happened. There won't be anything to rethread. What happens is the aluminum fitting bonds to the steel nut and when you loosen the nut the threads rip off. You need either a new cooler or a replacement fitting installed. .. sorry. "

[mannys9130]

Originally Posted by TnBob

Once again... from vstech.. who has forgotten more than many of will ever learn about MB's :

Most members here appreciate it IF you actually read responses to your query.

"If damage happened. There won't be anything to rethread. What happens is the aluminum fitting bonds to the steel nut and when you loosen the nut the threads rip off. You need either a new cooler or a replacement fitting installed. .. sorry. "

"Upper hose threads on both upper and lower cooler fittings"

I guess the reading replies is a 2 way street. His lower line won't thread onto the cooler, but his upper line will thread onto BOTH upper and lower. How can the upper line thread on the bottom if there are no threads left?

[TnBob]

Because the threads in the lower H O S E end are shot.

[Jim Condax]

Sorry if I caused any confusion with my statement about damaged threads. Only the outermost threads of the nipple were damaged as you can see in the picture. They cleaned up nicely with the die after this picture was taken. Thanks to all who posted trying to help me.

[TnBob]

Ahh yes.
''A nipple shall never be a nut''

[Diesel911]

What do the threads on the inside of the Hose Nut that will not fit on the Nipple look like?

This of course was on the old used Hose; on mine a piece of the Nipple stuck into the threads of the Hose Nut. That piece was corroded in place.

If the Hose that won't fit is a new Hose it could be someone messed up the Hose nut or even used the wrong Hose Nut during the assembly of the Hose.

[Diesel911]

Originally Posted by Jim Condax

Sorry if I caused any confusion with my statement about damaged threads. Only the outermost threads of the nipple were damaged as you can see in the picture. They cleaned up nicely with the die after this picture was taken. Thanks to all who posted trying to help me.

Lots of threads left; it looks good.