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Old March 2nd 07, 05:38 PM posted to rec.aviation.homebuilt
Dennis Fetters
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Posts: 108
Default Sealant for polyethylene fuel tank?

Charlie wrote:
Dennis Fetters wrote:

wrote:

On Mar 1, 12:55 am, "Rob Turk" wrote:

I'm looking for a sealant or kit to seal brass NPT inserts into a
polyethylene tank. This is a Kitfox header tank that has developed a
leak at
one of the inserts. I'm probably going to use Mogas that has ethanol
additives. Any hints, tips, thoughts?

Thanks,
Rob



Red high temperature silicon sealer. Local hardware store. Clean the
threads with alcohol and apply sealer. Lasts forever.


I'd check the label first. Last time I looked, it specifically excluded
use near gasoline.

The kinds I've seen will swell up & shed chunks into the fuel system.

Charlie



Correct Charlie. But you never use any sealant in an amount that will
transfer product into the tank.

Problem: The fellow has a polyethylene tank, which nothing likes to
stick to anyway. Add to that, it has fuel and maybe even oil in the
tank, making it worse. Can't use a sealant that hardens, it will crack
and leak.

Solution: Use RTV in a small amount on only the threads of the insert
after cleaning both the male and female parts. Install the insert so
none of the RTV goes into the tank. Allow the gas to swell the RTV
inside the threads, which helps the seal.

Right, it has drawbacks if not used correctly, but it is the only good
solution for the situation. The only other solution would be to ream the
hole out and replace the threaded insert with a Dapco rubber bushing and
insert, better anyway. You can find them at Aircraft Spruce.

Hope this helps.