Engine Oil Cooler Line Custom AN Hose (radiator port adapter fitting and reusing OEM lower metal tube sections)

[Horntoad]

My OEM engine oil cooler lines are leaking (at the crimps and at the quick disconnects - shocker, I know). Been planning to install custom nylon braided hose and AN hardware as a more reliable long-term fix. (stock RPO KC4 engine oil cooler)

My two questions are

1) My (possibly flawed) logic was that since I didn’t need to seal a separate inner metal tube (OEM-style – see photo below) to the radiator port I did not need a GM cooler/Saginaw/o-ring port adapter and would be able instead rely on the threads sealing my custom cooler line to the radiator port. (At the time I could not find a GM oil cooler/Saginaw-style adapter and didn’t even know what the name of that type of connection was to search for it properly.)

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Whereas, I do have an M20x1.5 X 8AN flare adapter already, might I be able to get a good seal if I use the proper thread sealant (e.g. Loctite 567)? Maybe not? Figured it might be worth a try; if it doesn’t work and leaks, swapping out those fittings for the GM oil cooler/Saginaw type would be straightforward.

Thank you specifically to @df2x4 for pointing out concerns about my chosen M20x1.5X8AN flare adapter and to @tayto for pointing out that the radiator port threads may not be designed with sealing in mind, for giving me a proper name for the fitting type (Saginaw aka GM Oil Cooler aka o-ring port), and for linking to a suitable adapter!

2) I’ve seen where folks (including @GoToGuy and YouTube Russell) have reused the lower aluminum tube sections from the OEM-style oil cooler lines (see photo below) when fabricating custom AN hoses.

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Are they using the AN sleeves and b-nuts to compression fit (not to a rubber hose but) directly to the aluminum tube (i've not included a photo example of this) and, if so, does that form a good, lasting sealing with simply metal-to-metal compression and no other seal/sealant between the AN fitting and aluminum tube? What are the potential problems going with rubber hose for the entire cooler line (GM must have opted for the aluminum tube section from the oil filter adapter and forward along the oil pan for some reason)? Whereas I already have the parts for full length nylon-braided AN rubber hose, is it worth my effort and additional parts to reuse the lower OEM metal section (while still subbing out the quick-disconnect fitting like Russell did), or can I comfortably go with rubber hose for the whole length?

You can see all the parts for my planned AN cooler line setup and some other discussion here. I have a second-owner (model-year 1995 Oct 16 build date) 1995 2DR 4WD 5.7L LS Tahoe with 149,650 miles.

 

[1952Chevy]

I went rubber from the engine, and kept a short section of tubing from the radiator. It seems to be working great.

 

[Schurkey]

I have little experience (one vehicle) with the OEM in-radiator oil coolers.

On my truck, the OEM hoses had steel sections. I'm told that the cheap aftermarket hoses (Dorman, etc.) use aluminum tubing. My truck has one oil cooler steel tube put back together with brass compression fittings. I had to cut the tube before removing the radiator. I could not get the tube nut to unscrew from the radiator until I had the radiator laying on the floor with no obstructions.

 

[GoToGuy]

Rather than getting a lot of " my buddies twice removed cousin did this ". You might want to review some " working with tapered pipe fittings" , " assembly of tubing with 37° degree AN style hardware". Much of your info is way off track. Instead of running a class, read some of the standard reference material available. It's all available on the net, either by standard industry practice, or from manufacturer online tech info.
Good luck.