Leaking AN fittings

[bjretired]

I just replace my oil cooler with a bigger one and changed out the hoses to braided steel with 8AN fittings. Started it up both fittings on the oil cooler were leaking. The ones on the engine were fine. The more I tightened them the worse it got. I just ordered two new 90 degree from Summit should be here Tues. Has anyone else had this problem? The oil cooler came with adapters pipe to AN. Looks like they are not making a good seal. I'm sure I smashed them over torquing....bob

Pic is pretty dark

[DWRAT]

Yes, I had the same problem years ago.
Tightening them didn't help.
You need new fittings and a very clean mating surface.
Don't over tighten.

[DonC]

Photo is too dark for me to see inside the nose but my vote for the culprit would be the pipe to AN fittings. Largely dependent on the mating surface angle of the male and female sides of the coupling. If one of them is a "bit off" they won't seal properly. The other area of possible problem is cross threading when assembling or debris around the shoulder of the female ferule.

DonC

[mikeinatlanta]

The pic doesn't show anything. Are you certain the leak is from the AN fitting? Everything I'm writing is if it is in fact the AN leaking.

The primary culprit for leaking AN fittings is attempting to force a misaligned fitting into place by wrenching on it. When properly aligned, you can run the nut almost all the way down using your fingers. When you force it down with a wrench it will tend to leak. When you attempt to correct the leak by over-torqueing the fitting you can cause permanent damage.

First step is to examine the male for obvious deformation and the female for a crack.

Reinstall the fitting with it properly aligned such that you can run the nut all the way down with your fingers.

Tighten to the proper torque for the fitting size. Do not over-torque.

If the fitting is undamaged, this will correct the issue. If there is some sealing surface deformation it will not.

If the fitting continues to leak, reassemble with a 37 degree conical sealing washer. If the leak continues, you most likely have cracked the female fitting.

[jhv48]

Conical sealing washer did it for me too.

I think I got them from either Jegs or Summit. Made by Earl's. Cost about $10.

[itstock]

I have had bad AN fittings of all different brands.

[mikeinatlanta]

Originally Posted by itstock

I have had bad AN fittings of all different brands.

Interesting. 35 years in aviation and a lifetime playing with cars and bikes and never had one. Very lucky I guess.

[rodneym]

I never would have suspected an alignment issue. They can be fussy, especially assembling the Teflon coated lines.

Something stuck out, though. -8AN for oil lines?

[Gaz64]

Originally Posted by rodneym

I never would have suspected an alignment issue. They can be fussy, especially assembling the Teflon coated lines.

Something stuck out, though. -8AN for oil lines?

Agree, I would fit -10AN, and others have -10AN.

[mikeinatlanta]

Originally Posted by rodneym

I never would have suspected an alignment issue. They can be fussy, especially assembling the Teflon coated lines.

Something stuck out, though. -8AN for oil lines?

Good catch. I'm running -12. -8 seems a bit small, but without running the numbers, maybe it's ok for his setup.

[itstock]

Originally Posted by mikeinatlanta

Interesting. 35 years in aviation and a lifetime playing with cars and bikes and never had one. Very lucky I guess.

You must be. Is there any certain brand that you prefer to use?

[mikeinatlanta]

Originally Posted by itstock

You must be. Is there any certain brand that you prefer to use?

Not really. I use mostly Aeroquip and Fragola on the toys. What ever they buy in aviation. IMHO, buying Chinese junk for what is supposed to be high end componentry is a bit of an oxymoron.

[itstock]

Originally Posted by mikeinatlanta

Not really. I use mostly Aeroquip and Fragola on the toys. What ever they buy in aviation. IMHO, buying Chinese junk for what is supposed to be high end componentry is a bit of an oxymoron.

I'll send you a couple grade a fragola fittings if you want them. Maybe your luck is better than mine.

I haven't had any straight connectors fail at least.

[mdross1]

Originally Posted by mikeinatlanta

Interesting. 35 years in aviation and a lifetime playing with cars and bikes and never had one. Very lucky I guess.

Same here never a leak. Before and after I make up all hoses always check sealing surfaces. Another lucky one,
knock on wood!!

[strictlypersonl]

I don't have the thread specs here, but British JIC fittings might have the same thread size, but they have a different cone angle.

[BevanWright]

You can get a Loctite sealant that I use on some of my fittings, particularly ones that are removed often like the ones on my dry sump system. This stops the weaping.

[DougD]

These an fitting washers work great when you have a leak:

https://www.pegasusautoracing.com/pr...p?Product=3202

I had the exact same problem with my oil cooler fittings and these solved the problem. Just disassemble the fitting, place one of these soft washers on the fitting, and reassemble. Voila!

[bjretired]

Thanks guys. I replaced the fittings with summits. Got the conical washers just in case. I over tightened the first set of fittings. (my fault) It's been years since I worked on aircraft but I could swear that the AN fittings were a lot stouter than what I seeing now? Now on to replacing the steering column.......

[lippy]

I used mostly Aeroquip and haven't had a problem with any of them. I just snug them relatively lightly and no leaks in the oil system or the fuel system. What I like about the Aeroquips is that they assemble to the hoses in a way that is binary and you sort of know they went on right and tight. I didn't get the same feeling with the other brands I used.