AN Fittings are Leaking!!

[badazz81z28]

I'm trying to start the engine and the AN fittings on the fuel line are leaking. At a connection in the back it was leaking, so I re-made the line, installed it and the leak is gone, but now the other side that wasn't leaking before is now leaking! WTH!!

What am I doing wrong? All I did was disconnect a good line to repair a bad one and now it's leaking! Gas is everywhere!

[fast98]

So it's leaking where the hose is going into the fitting? Are you using hose and fittings from the same manufacturer? Are the fittings the correct style for the hose?

[badazz81z28]

These are on SS 3/8" line with tube nuts and sleeves on AN couplers, All metal, no hose. Same manufacture (Fragola)

The fitting wasn't leaking before I swapped it out to fix another line, I disconnected it and re-connected it and now leaks.

[MonzaRacer]

OK question is if you are using a flare,,,, are they double or single. Single hardly ever seal good without help of some sort, and doubles on ss tend to split at tube seam.
If not split you might look around for copper sealing washers for 37degree flare

[MrQuick]

Another reason why I don't like using SS lines. It is most likely cracked...try to tighten more the crack gets longer.

[badazz81z28]

OK question is if you are using a flare,,,, are they double or single. Single hardly ever seal good without help of some sort, and doubles on ss tend to split at tube seam.
If not split you might look around for copper sealing washers for 37degree flare

I read that on line last night...I gave up and bought was is call a "Conical Seal". They are Aluminum though.....I hope they work as well as copper would have doh!

These are 37 degree single flares.

[badazz81z28]

Right now I'm down to 1 leaker out of 5 connections.

[sjaroslo]

You might have the Fragola catalog and I'm not certain that I believe them myself (I'm not there yet) but here goes:

"Many people overtighten the aluminum fitting on the adapter, which distorts the 37 degree seat, and may cause a leak. Both the threads and the seat surface should have a drop or two of oil to smooth the tightening process. The maximum torque specifications are listed here. (An alternate method of tightening is to bring the nut to 'hand tight' and then rotate it another 1/4 turn with the proper wrench)"

Fitting Size - Max Torque in Foot Pounds
-3 - 8.75
-4 - 11.5
-6 - 16.25
-8 - 29
-10 - 35
-12 - 45
-16 - 70
-20 - 85

[badazz81z28]

You might have the Fragola catalog and I'm not certain that I believe them myself (I'm not there yet) but here goes:

"Many people overtighten the aluminum fitting on the adapter, which distorts the 37 degree seat, and may cause a leak. Both the threads and the seat surface should have a drop or two of oil to smooth the tightening process. The maximum torque specifications are listed here. (An alternate method of tightening is to bring the nut to 'hand tight' and then rotate it another 1/4 turn with the proper wrench)"

Fitting Size - Max Torque in Foot Pounds
-3 - 8.75
-4 - 11.5
-6 - 16.25
-8 - 29
-10 - 35
-12 - 45
-16 - 70
-20 - 85


I know something else is up...In fact if you tighten it by hand and turn it 1/4 more turns, that's a lot! I tightened them by hand and just a snug more.

All my aluminum fittings are leak free, its this one stainless on stainless section. I just took the line off tonight, re-made the flare, perfect...still leaks. Could the union be defective? I'm telling you before I took the line off a repaired the other side, this side wasn't leaking....now it is...interesting.

[53Vipette]

OK question is if you are using a flare,,,, are they double or single. Single hardly ever seal good without help of some sort, and doubles on ss tend to split at tube seam.
If not split you might look around for copper sealing washers for 37degree flare


All 37° fittings are single flare. 45° fittings are the double flares.

[53Vipette]

I know something else is up...In fact if you tighten it by hand and turn it 1/4 more turns, that's a lot! I tightened them by hand and just a snug more.

All my aluminum fittings are leak free, its this one stainless on stainless section. I just took the line off tonight, re-made the flare, perfect...still leaks. Could the union be defective? I'm telling you before I took the line off a repaired the other side, this side wasn't leaking....now it is...interesting.

Do you have pics of the fittings and line? Typically, on aircraft if we can't get a line to seal with a conical washer and correct torque specs we replace the line. I've had several flares not form correctly and ended up more bell shape. I found that the cheap tool you buy from the parts houses allows the tube to slip slightly and leave striations on the outside of the tube that keep the tube sleeve from seating fully on the flare. If the tube is cracked and you make a new one use a small countersink in a hand drill to de-burr the end. If you get chattering from the drill you can spin it by hand for better results. I hope this was helpful and not to wordy.

[David Pozzi]

I've had stainless hard line that leaked at the flaired ends due to the internal seam protruding. I machined a 37 degree tool I can chuck in my drill. I use valve lapping compound on it & spin it in the flared end.

[Jim Nilsen]

I've had stainless hard line that leaked at the flaired ends due to the internal seam protruding. I machined a 37 degree tool I can chuck in my drill. I use valve lapping compound on it & spin it in the flared end.

I experienced this when I was firing up my car. The seam just doesn't seem to go flat like the rest of the flare. It in fact actually looked like a crack until you get out the magnifying glass.What looks like a crack is actually the ridge of the seam. I just sanded mine down with some 300 or 400 wet dry sandpaper over the end of the male fitting so it was already shaped for the flare. It took a bit because the stainless is so hard but when you get there to the point it won't leak the seam disappears to the same level. On one of my 1/2 flares i had to get the file out and take it down because it was so high and so hard.Definately get a magnifying glass so you can truly see what it looks like.

Good luck and with some persistance you will get it to seal with out having to make a new line.

One more thing, putting a little bit of light oil on the threads really does help in getting them the right torque.

[bronx_peanut]

Try using one of these http://www.jegs.com/i/Earl%26%23039%3Bs/361/165106/10002/-1 I used it on my project and no leaks for 2 years.

[TonyHuntimer]

Pictures would really help...if you have not fixed the problem yet.

Tony Huntimer
TonysSpeedShop.com

[badazz81z28]

Pictures would really help...if you have not fixed the problem yet.

Tony Huntimer
TonysSpeedShop.com




Sorry for a lack of an update. I ended up installing an Earl's AN Concial Seal. Sealed it right up. If I was guessing, I bet it was the seam in the tubing.