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Fuel Tank Leak

VF84Sluggo

Well Known Member
My new-to-me RV-4 has developed a right-side fuel tank seepage/leak (amazing how airplanes can just sit in a hangar and break!) The tank has been defueled, so no worries about seeping/leaking fuel becoming a fire hazard.

I've taped an arrow pointing at where is suspect leak/seepage is coming from. It looks like there may have been a problem here before, seeing as how there's a heavier buildup of external sealant in the suspected area.

This begs the question: is it possible to get an external application of a sealant to adhere and seal? If externally sealing is possible, what sealant to use?

Or is a "fix" like that destined to fail, leak again?

Thanks in advance.
 

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To my knowledge no one has yet figured out how to externally seal a fuel tank that lasts long term. Luckily for you this area will be easy to access. Since the RV-4 doesn’t have Z brackets go ahead and pull the tank off the wing for access. Going in through the access plate, drill out the rivets attaching the leaking bulkhead, then reseal it properly.
 
Fuel Tank Sealer

Use PR-1422B2.
If ordering from Aircraft Spruce make sure they have some in stock. They were out last time I tried ordering and it was a mess......
 
Pro-Seal gets soft when exposed to fuel and air cycles. This does not happen in the tank because there is enough vapor pressure to prevent it; however, external Pro-Seal that is exposed to fuel vapor will soften. I have seen it several times.

After you have drilled out the rivets, Use a putty knife lubricated with MEK (lubricate often, like every 10-15 seconds) to remove the plate by rocking it back and forth with slight forward pressure. Clean it with scottchbrite, Grind a chamfer on the bottom side of the plate to make it easier to remove in the future (you will understand this better as you start to try removing the plate this time and see that the problem is getting under the edge.
 
Good info, gents. Thanks much.

Yes, to do it right, make a lasting seal, it looks like a tank removal is in my future. Gonna need help with that, as I am not the builder and have never done tank work.

I suspect that this was a "weepy" area some time in the past, as it looks like an externally-applied heavy application of sealant was done on that sectgion of the flange.
 
I see. Thx!

Is there any difference in the sealing "strength"? Does the slow-cure create a better bond/seal?
 
Flamemaster vs. PPG

Lots of endorsements here on numerous Polysulfides. Flamemaster and PPG are readily available with a big price difference. Is there any real world experience out there to comment on the difference ?
 
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