Hi--

I've have a -6 oil cooler that I'm trying to return to service. The cooler came out of a running car and although the outside is dirty, it shows no sign of damage, oil leaks or of an engine making metal. With a somewhat clean bill of health, the next step was to remove the oil-line to cooler fastener nut. But before I started, I search World and talked to forum members who have had success removing the nut. Following their leads, I bought a 32 mm open end wrench and had it thinned by a machinist to ~ .330" (to fit the space available).

After soaking the nut with Kroil for several days I attempted to use the modified open-end and a 36 mm box-end wrench to loosen the nut. The oil-line nut didn’t come close to moving. I also tried an industrial strength heat gun to heat the nut. Again, even with the heat, it remained locked in place. Based on my "feel" for the amount of torque I was applying, I was afraid that I would ruin the cooler. At that point the oil-line, already cut off, and the threaded fastener and nut became totally sacrificial. Using a Dremel tool, I slit the oil-line fitting on both sides and cracked it open enough that it broke away. I expected the fitting was swaged on but was surprised to find that fitting is threading, suggesting that you might be able to unscrew it and saving it for future use.

Removing the oil-line opened up the oil-line side of the fastener nut which was still attached to the cooler. I tried soaking both sides with Kroil again for a couple of days but removal was still a no go. Again using the Dermal tool, I slit and broke away the back side of the nut, working the Dremel from flat to flat. I used a flat blade screw driver to pry the slit sections of the nut away, when I finished, the entire back of the nut was removed. Note: Looking into the oil-line seal area gives you a good idea how much of the back of the nut you can safely remove while staying away from the sealing surface of the threaded cooler connection. With the nut removed the internal seal/ barbed fitting of the oil-line lifted away and the remainder of the nut turned off by hand. A quick look at the photos should take you the rest of the way.

The next step is to pressure test the cooler. I’ve seen a couple of photos testers but don’t know where they can be purchased. Does anybody have a tester they can lend me or know where I can buy one?

Any questions, let me know.

--Papermaker

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Here's what we use to pressure test but I would stop by a shop and see if the will do it for you. Takes 2 minutes.

https://www.stomskiracing.com/products/911-oil-cooler-tester

Hi mepstein--

I wish there was a Porsche or independent sports car business within reasonable driving distance (the closest P car business is between 60 - 90 miles away).

Thanks for the tester link, I'll check it out.

--Papermaker

Any place that services airplane engines will have, or know where to have it sonic (sp?) cleaned. They pre. test it, cycle clean it, until it is perfectly clean, and return it to you. Any time a bearing failure, etc. happens this must be done. I'v used a few different companies, but by googling it, you may find a place locally.

Don't sweat too much they aren't known to have leakage issues unless knocked around,had 2 done and no issues....however they do hold a lot of crap inside so an ultrasonic clean is a must do.
Good skills removing that compression nut

Thanks tomrev and porschetub for the tips. I'll check into the FOBs around the area to see if they offer ultrasonic cleaning and pressure testing.

Also, the oil-line nut removal worked extremely well. As I broke the last piece of the nut away the barbed oil line fitting just fell out and the nut screwed right off by hand!

--Papermaker

The oil line fitting that you removed is a beautiful piece of equipment.
They are rebuildable and are usually date stamped.
As can now be seen they are designed to be disassembled to replace deteriorated hose.
Your difficulty with the attaching nut can usually be overcome with a single cutting wheel slot across the thinnest portion of the nut in the direction of oil flow. It can definitely be done with two cuts while also saving the working parts of the fitting.
IIRC replacement nuts are/were available. Hose is definitely available.
Currently available replacement hoses have crimped fittings and are a concours/restoration eyesore.
Good job on taking your time and not damaging the cooler.

rgalla9146--

Thanks for your comments. Maybe, I should have added more detail. The fitting had a 1/2" crack at the tapered end which made the decision to cut it in half easy. I added the note to warn others to try unscrewing it before cutting it. I considered cutting the nut across the compression nut flats and experimented with a few cuts but ultimately I felt that I couldn't guarantee that I wouldn't cut through the nut and into the cooler threads so I used the method that didn't damage anything of value.

--Papermaker

easy to make your own tester - just need a thick (3/8" or so) flat piece Of alloy & drill a few holes in it - install a metal tire air valve & a gauge fitting as seen above - use oem seals

fwiw - i had one some yrs ago that leaked - had a split seam up inside it - just a tiny steady drip, but it landed on the headers & smoked a lot - sold it real cheap to a guy who tho't he knew how to fix

Hi larryM--

I just built a similar tester for a Moto Guzzi Eldorado oil pressure relief valve so I'd like to do the same here. What did you use to seal the female threaded connector on the cooler? Note: The Stomski website recommends starting at 25 and increasing pressure to 50 - 75 psi.

Thanks,

--Papermaker