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Fuel screen fitting leak

1001001

Well Known Member
After sealing up my second fuel tank, I have a persistent small air leak on the tank. I have traced it to the threads on the tank discharge fitting. This is the bulkhead fitting, 3/8" NPT, with the fuel screen sealed into it.

The leak is definitely around the threads of the fitting. I have removed, cleaned, and sealed it with pipe thread sealant (Loctite 592) three times now, and it still leaks. Inspecting the threads, they appear to have been damaged during the original threading operation at the factory, a fact I missed prior to installation and sealing. Specifically, in the threads deeper into the fitting, there is a chunk of thread missing, and I think this is causing the issue. I have gently run a 3/8" NPT tap in to clean up the threads, and this resulted in making the leak slower after reinstallation, but it's not gone. When the tap reaches the damaged part of the thread, it gets really hard to turn, and I'm afraid I will damage the threads further if I persist.

I think the problem could be fixed by removing the threaded fitting, cleaning thoroughly, and applying tank sealant to the threads. I think this will seal better than the loctite 592. However, it may permanently seal the fitting to the tank.

How often (if ever) does one have to pull this fitting to clean the screen, or for other purposes? My only other option appears to be cutting an access hole in the tank, removing the fuel fitting flange, and reinstalling a new one. I have an access plate kit on hand but not a new flange. I'd absolutely rather not cut into the tank at this point.

Any thoughts?
 
I am having exactly the same issue with my left tank. I have replaced the rock strainer three times now, and the hard line to the aircraft twice.

Today I am leak testing. Again. The leak is so slow that the balloon stays inflated for 10- 15 minutes. I will get a small bubble at the fitting to tank connection. I tried proseal and locktite both, to no avail.

How did you, or anyone solve this issue?
 
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