I finally got around to replacing the oil cooler lines on the '78 300cd this past weekend. I used a liberal amount of PB on the fittings before hand seeing that my recent escapade with the leaking WP housing uncovered many frozen bolts. Overall, it went like clock work - but the one thing that concerns me slightly is the lower oil cooler line fitting was frozen.

I used a reasonable amount of elbow troque and a wrench on the actual oil cooler fitting to counter the force, along with a bit of heat applied to the oil cooler line nut to eventually get it off. Upon inspection, it seems like 2 or 3 of the threads along the middle of the fitting were stripped, but not enough to be a huge concern. I was able to put it back together with new lines, although the lower line was tight the entire way in (like it was on the way out). Driven the car around 100mi since then and no issues so far.

I guess my question is whether I should be concerned about anything, seeing that the oil cooler fittings are notorious for stripping/breaking. Has anyone encountered anything similar to me?

I suppose I could've taken extra time to fix the fitting, but time is a luxury as I started a new job. Thanks for any input.

After driving it for a while and you stating no issues, then you should be ok. I'd just periodically check for leaks.


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If the remaining threads generate sufficient force to allow the fitting to seal, then you're fine. The science of threads is a bit of an art and the forces generated by a set of threads are usually much greater than necessary, especially in this application.

If it doesn't leak today, it won't be an issue in the future.

Just curious, how does one repair/replace one of these fittings? I'm going to be tackling this job and knowing that stripped threads can be fixed will make my heartburn much less as I start in on it.

Here is a link to the issue
Engine oil cooler and hose/line issue, link thread



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Thanks!

There is Threads in the DIY Secton with nice pictures on the Repair. However, one of our member said that if you grind a one or 2 slots length wise through the metal on the Oil Cooler Line Nuts you can split the Nuts and avoid the stripping issue altogeather; details in the DIY section.

You can read Hunters Thread for more details on the Tools needed. On the 617.952 the Fittings you use to replace the damaged Oil Cooler Nipples are the same Fittings that the Oil Cooler Hoses screw into the Oil Filter Housing.
That means you can get them at a Junk Yard for a few Dollars. Although they are not terribley expensive from the Dealer something like $11 each.

You can get the Tap at OSH Hardware or Sears at a resonable price but you are better off getting the reduced Shank Drill Bit online due to Cost on the Internet.

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The repair is refered to as "screwed nipples". or do a search on Screwed nipples.

oil cooler cross threaded...

when I replaced my oil cooler hoses, I used some Anti-Seiz compound on the threads.

Charlie

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Thanks for the feedback and for re-affirming my thoughts. I did use some anti-seize on the threads upon re-installation, but obviously it was pointless on the lower line fitting. Overall, it seems to be holding up, so I suppose I can quit worrying about this when I'm cruising down the highway.