Looking for solutions to fix a leaky drain fitting...

[bjdecker]

<sigh>

The fuel drain flange, VA-112, on my Left QB Tank circa 2015 (Philippines), decided to spring a leak and ruin my high-$$$ paint job

View attachment IMG_0247.jpeg



And, pressurizing the tank slightly and spraying a mixture of soapy water on the flange revealed the end of the leak path:



Looking inside the tank, it appears that all the rivet tails are neatly encapsulated in "pro seal"...





I suspect the source of the leak is the flange-to-skin interface at the top of the NPT annulus..

I'm looking for ideas/options on how best to fix, here's all I've come up with...

1. Drill out the 6 rivets, pop off the flange and clean the mating surfaces. Upsize the holes to #30, countersink flange holes to 120° and install AK-42H "tank" rivets with a generous application of "Proseal" between the skin, flange, rivet bodies, my skin, hair, fingers, wheel pants, refrigerator handle...

2. Apply a slight vacuum on the tank and apply "thin" sealant to the leak path; glue the channel shut? Which sealant works here?

3. Other ideas?

Thanks in advance y'all.

 

[jabarr]

Option #2. Locktite 290

 

[Ralph Inkster]

That's a pretty aggressive leak!

3. Yank it. Open it. Fix it properly.

If 1 or 2 done today, you will be performing 3 next year (with a truly glorious stain to repaint, again. & real potential of dumping 20 gallons on the hangar floor)

 

[RV7CardenMike]

<sigh>

The fuel drain flange, VA-112, on my Left QB Tank circa 2015 (Philippines), decided to spring a leak and ruin my high-$$$ paint job

Brian, when I built my tanks I had a very small leak around a rivet. I diluted some Proseal with TOLULENE and drew a slight vacuum on the tank. I was able to massage the thinned Proseal around the rivet and due to the slight vacuum, (be careful of too much vacuum) and I could actually tell it was being drawn into the inside of the tank. The toluene would flash off pretty quickly, leaving the Proseal to set up. I gave it a couple days and then re-tested. No leaks. If that didn't work I was going to try the Locktite next.

 

[Norman CYYJ]

Brian, when I built my tanks I had a very small leak around a rivet. I diluted some Proseal with TOLULENE and drew a slight vacuum on the tank. I was able to massage the thinned Proseal around the rivet and due to the slight vacuum, (be careful of too much vacuum) and I could actually tell it was being drawn into the inside of the tank. The toluene would flash off pretty quickly, leaving the Proseal to set up. I gave it a couple days and then re-tested. No leaks. If that didn't work I was going to try the Locktite next.

Carefully drill out the rivets, remove the flange. Clean the flange and scotchbrite both the flange surface that mates with the skin and do the same to the skin. Then smear proseal on the skin and flange filling the rivet holes with proseal with the same size of rivet rivet the flange back on. After it is riveted back on wipe the surplus proseal off around the flange edges to make it look pretty. Also run a shop rag into the threaded hole to clean any proseal out of the threads. That should fix the leak.

 

[lr172]

#1

Imo, You do not need to seal from the inside to have a leak free seal, assuming you take care to do it the right way. That is the way we install the rear baffle. I would not recommend trying to suck anything in with vacuum.

 

[bruceh]

Seeing that the leak is not the rivets, but instead the threaded bung to the tank skin, why not just try getting some sealant around the threaded hole/skin?
I have no experience with the Loctite solution, but that or some thinned sealant would be a first start. If it still leaks, then I would remove the tank, go in from the fuel sender hole and reseal from the inside.

 

[mburch]

I had one of mine weep fuel at the skin/flange interface, although maybe not quite as bad as yours. I solved it with Loctite 290:

1. Clean exterior surfaces
2. Dab on some Loctite and let it wick in
3. Leave it alone for an hour or two
4. Wipe off the excess with a paper towel (don't use solvent)
5. Repeat steps 2-4 a bunch of times over the course of a week

I didn't do anything special with air pressure, just left everything at ambient. So far so good, no more leaks.

 

[bjdecker]

Seeing that the leak is not the rivets, but instead the threaded bung to the tank skin, why not just try getting some sealant around the threaded hole/skin?
I have no experience with the Loctite solution, but that or some thinned sealant would be a first start. If it still leaks, then I would remove the tank, go in from the fuel sender hole and reseal from the inside.

In addition to wicking in Loctite 290, I am considering this:

1. Remove the CCA-110/CAV-110 QD fitting
2. Chase/Clean the threads in the flange
3. I made this tool:



It's a 3/8" piece of steel, threaded to 1/8"-27NPT, 0.063" longer than the threads in the flange.

4. Place a bead/dollop of proseal around the end and first 2 threads of the tool
5. Install tool into the flange. Let cure for 1-2 days
6. Remove tool. Using a #12 drill and 3/8" bushing, drill out any proseal that has cured "across the top" of the opening at the skin.
7. Install CCA/CAV-110 and leak test.

Thanks for the advice everyone. I'll follow up with results.

B

 

[terrye]

Seeing that the leak is not the rivets, but instead the threaded bung to the tank skin, why not just try getting some sealant around the threaded hole/skin?
I have no experience with the Loctite solution, but that or some thinned sealant would be a first start. If it still leaks, then I would remove the tank, go in from the fuel sender hole and reseal from the inside.

^^ This

 

[terrye]

Brian, I don't think your proseal / 1/8" NPT tool idea is a good one. Too easy to get proseal bits floating around in the tank. I would try bruceh idea first, then if it leaks in the future, remove the VA-112 and seal it between the flange and skin.