leak around fuel sump

I have a tiny leak around the fuel sump fitting. Looks like it is coming through the sealant layer on the edge of the fitting. It is not coming from the fuel sump itself. Barely would have noticed except for the trace of blue dye. It wasn't there when the plane was DAR inspected last friday. My tanks were part of QB wings so I have very little experience with fixing something like this. By the way, the wings are on the plane and I'm flying. Any suggestions on the best approach? thanks, Jack N489JE 9A flying.

If you are refering to the sealant on the threaded portion of the quickdrain fitting, you may need to remove the fitting and apply more sealant to the fitting and reinstall it.

If you are refering the the flange of the wing sump that is riveted to the tank with sealant, then other means like opening the tank end coverplate and cleaning and resealing the sump fitting from the inside might be necessary.

Also check to see if particulate may be caught in the quickdrain causing it to not seal properly. I had pieces of AL working their way out of my QB tanks and catching in the quickdrains. I had to flush the tanks several times by pulling the drains and letting fuel gush out and purge the particulate out. I replaced the O-Rings several times before the seepage finally stopped. It helps to have and extra quickdrain ready to install, or a plug, so you don't lose to much fuel. Roll your sleeves up!

Roberta

I have used Pro-Seal externally on several occasions to stop leaks. If you can clean and sand the seam around the leaking fitting ,then apply Pro-Seal in a fillet all around the fitting it should work. You should drain the tank first. Just go fly and burn it out !
Let the Pro-Seal cure a couple of days if you can before filling the tank.

Bob olds RV-4
Charleston , Arkansas

Fix That Leak

Build9A said:

I have a tiny leak around the fuel sump fitting. Looks like it is coming through the sealant layer on the edge of the fitting. It is not coming from the fuel sump itself. Barely would have noticed except for the trace of blue dye. It wasn't there when the plane was DAR inspected last Friday. My tanks were part of QB wings so I have very little experience with fixing something like this. By the way, the wings are on the plane and I'm flying. Any suggestions on the best approach? thanks, Jack N489JE 9A flying.

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My leak between the fitting and the skin was small but the blue dye makes a mess. The fitting was fluid tight for years until I wrenched on the drain fitting to drain the tanks. The torque from removing and reinstalling the quick drain fitting started the leak. My fix was to remove the paint, clean it well with MEK. Rough up the area where sealant will go real well with a scotch bright pad, sand paper. Get right into the corner with a small metal brush and etching sloution. I agree with Bob Olds instructions. Work slowly. Make sure the edge of the fitting and 0.30? of the skin around the fitting is clean, clean, clean. MEK and etching solution are good choices. After it is clean, clean it again. Oh yes, did I say clean it well. You can't have any fuel residue. Using a bead of pro-seal, make the fillet go all around the whole fitting. You don't want it to wick around the edge. The fillet does not have to be huge, just enough to fill up the edge of the fitting and out on the skin about 0.20". You can put the pro-seal in a plastic bag and cut a small corner off and use it to apply the sealant. As Bob said don?t tank up for a few days and consider a low watt light on the floor nearby to keep it warm. Just make sure it is cured before you use it. Depending on temp and how much catalyst you used, it could take a week or more to fully cure. Push it with you fingernail and it should be real firm and not leave a mark. Don't over do the catalyst to make it cure faster. The fillet fix I did on my tank made it somewhat more aerodynamic. Touching up the sealant with paint made it looked OK, but best of all it stopped the leak. (Note: You will only need a very small amount of Pro-seal, MEK or etching cleaner, so find someone who can donate a little material. It takes a little practice mixing and applying Pro-seal, so experienced help would be nice. It is messy and gloves and thinner on hand is good to have for cleaning. This is an OK fix, but the best method would be remove the tank, access cover and remove the fitting and start over, but that would be a hassle. Try the external fix first, it should work. Cheers George