Leaking VA-141 Fuel Pickup

[echozulu]

I found a leak on my left tank, and traced it down to the fuel pickup. After draining the fuel and pressurizing the tank with air, I found bubbles coming from around the fuel pickup. I disassembled and installed a brand new VA-141 I had lying around with Loctite 567 thread sealant. Let it cure for 24 hours, leak tested and reintroduced fuel. Now a week later it's leaking again. Stuck a borescope down there and there's still a ring of the thread sealant around the fitting but the thread sealant on the top side is tinged with blue dye.

Vans says to use 567 for thread sealant, but I'm suspecting it's not curing properly. Is there another sealant that's better? I was reading the datasheet and apparently we need an activator to go with the Loctite 567 when applying on aluminum?

 

[Bavafa]

Loctite 567 does not cure and that is the beauty of it and should seal if the leak is from the thread. I would try it one more time, perhaps with a more generous portion of the Loctite. Alternatively you can use Proseal but that may make the removal of the fitting more difficult if you need to remove it. One thing to consider, which I had experience with helping a friend, the VA-141 could crack if the NTP fitting is pushed too far in. We used proseal and it stopped the leak.

 

[Ralph Inkster]

Had to replace both flanges on the last 2 tanks I repaired. Reason- both were over torqued & cracked.
I saw they were unavailable so milled replacements up out of some 7075 I had laying around. Can’t have AOG aircraft clogging up my hangar, can I.

 

[lr172]

I found a leak on my left tank, and traced it down to the fuel pickup. After draining the fuel and pressurizing the tank with air, I found bubbles coming from around the fuel pickup. I disassembled and installed a brand new VA-141 I had lying around with Loctite 567 thread sealant. Let it cure for 24 hours, leak tested and reintroduced fuel. Now a week later it's leaking again. Stuck a borescope down there and there's still a ring of the thread sealant around the fitting but the thread sealant on the top side is tinged with blue dye.

Vans says to use 567 for thread sealant, but I'm suspecting it's not curing properly. Is there another sealant that's better? I was reading the datasheet and apparently we need an activator to go with the Loctite 567 when applying on aluminum?

the 10 tanks have a threaded flange riveted into the rib with proseal keeping it leak free. given those symptoms, its likely your leak is coming from the interface between flange and rib (sealant failure) and not from the threaded fitting.

 

[lr172]

Loctite 567 does not cure and that is the beauty of it and should seal if the leak is from the thread. I would try it one more time, perhaps with a more generous portion of the Loctite. Alternatively you can use Proseal but that may make the removal of the fitting more difficult if you need to remove it. One thing to consider, which I had experience with helping a friend, the VA-141 could crack if the NTP fitting is pushed too far in. We used proseal and it stopped the leak.

actually, it does cure. it is an anaerobic sealant, which means it only cures in the absence of air/O2, so any extra that squeezes out will not cure and create problems.