BRAKE LEAK

[Barry_Barry]

Hi Gang:

I have aluminum brakes lines on my system. I have developed a STRANGE leak... Here is what is happening:
1 - Normal Brake Pressure -NO Leak
2 - High Pressure and HOLDING - NO Leak
3 - When I RELEASE the brakes after High Pressure - There is a small leak at the TOP of the AN Nut.
Question: Why is the leak showing up ONLY when the High Pressure is RELEASED?

In trying to repair this I:
1 - Removed the Aluminum tubing.
2 - Cleaned the Fittings.
3 - Inspected under a magnifying glass - Found small burrs.
4 - Cut off the Flair with the burrs.
5 - Installed New Ferule and Nut and Re-Flared the end.
6 - Tested as above and the leak was REDUCED but still a leak.

Any ideas?

AND!!! Why would it leak ONLY with High Pressure being RELEASED?... It does NOT leak with the high pressure applied... ONLY when RELEASED?

Barry
[email protected]

 

[snopercod]

It sounds like the flare and the AN fitting aren't matching up perfectly. I certainly don't mean to offend you by asking this, but are you sure you were you using a 37 degree flaring tool? It's easy to grab a 45 degree tool by mistake. No offense meant. Vans lists the proper torque values for the Aluminum B-nuts here: https://www.vansaircraft.com/pdf/Torque_Spec_Aluminum_Fittings.pdf although those are higher than the FAA recommendations: https://www.faa.gov/regulations_pol...craft/amt_handbook/media/FAA-8083-30_Ch07.pdf . I don't know which is correct.