how to repair leaking fuel tank?

Hi folks,

yet another set back for Hill's Air Force. I filled & calibrated the pre-assembled fuel tank last weekend, only to discover a leak. The tank came out yet again and was put on th bench for leak testing. Pressure testing (balloon, bike pump & bubble soap, per chap 37) was not successful in locating the leak. (I think my fuel cap is no longer air tight, despite plugging the vent with a 4-40 screw as suggested by someone else.)

Filling the tank with 18 gal revealed not 1, but 2, separate leaking spots. Both are very slow, but clearly present. Both are at corners: lower left front and upper right front.






Question: How should I go about making repairs to these corners? The obvious (to me) approach is to scrape/clean off the pro-seal in these areas and get down to the bare metal; clean & scuff the metal as per chap 37, then liberally apply pro-seal; and finally renew my conversations with the deity of my choice.

The other approach (which I'm hoping to avoid) is to remove the front panel from the tank in order to attempt repair from both the inside, and the outside.

Am I missing anything? Is it even reasonable/possible to repair these kinds of 'pinhole' leaks?

As always, thanks in advance for all advice,

Can you get at them from the inside by removing the large plate the fuel sensor is mounted on? I initially had a small leak I was able to get at that way.

Did you purchase the tank pre-built from the factory?? I would think Vans would make it right since it's a new tank and never flown....

KALEWIS said:

Did you purchase the tank pre-built from the factory?? I would think Vans would make it right since it's a new tank and never flown....

Click to expand...

Ooops, I missed that part. Kyle's right, if it's pre-built they should make it right ...

Fixing a leaking tank

First of all, don't laugh at this repair because I have done it at least six times to one of my tanks. I should mention that my problem was caused when I stripped the tank to repaint (after 11 years of flying) and too much paint the first time around. The result was a number of areas where paint was chipping off. The stripper apparently "ate" its way into the recess of the rivets and even though I washed the tank several times before painting, there apparently was a residual amount remaining around the rivet heads.

In time, the stripper "ate" through creating a vapor bubble with a small leak developing around the rivet heads. Since stripping it the last time I was reluctant to do so again. On a pure guess, I decided to cut through the paint (it is a base coat clear coat) to the aluminum with an Exacto knife in an X pattern. Once this was done, I lifted one of the "paint petals" and squeezed Harbor Freight's brand of Crazy Glue which is in a gel form and made sure it covered the bare aluminum rivet and then pushed the "paint petal" back down and let it dry. (Yes it does leave a slight bump but it matches the paint so it's not objectionably visible) Believe it or not, it fixed the leak.

I see that your leak is not visible to the outside and before you go to any labor intensive "fix", give it a try. The key is to use the gel form, clean the area of any residual fuel (acetone works well) apply the glue and let it dry. It's a cheap fix and if by chance it doesn't work for you, your only out a couple of dollars and very little labor. Good luck!

When I rebuilt my tank I found one weeping rivet down in the lower front inboard (thank goodness) corner. I used a syringe to force some sealant into the rivet. Roughly 70 flight hours since then and no leaking. My point is, some leaks can be sealed from the outside. But I'd call Van's and discuss it with them. If I'd paid for a prebuilt tank I'd expect one that doesn't leak.

Even though the plans do not discourage it, whatever others might say, DO NOT TIG weld the leak while it is full of fuel

This will do a good job of sealing a small leak from outside surface. http://eclecticproducts.com/downloads/tds-seal-all-english.pdf

I had a small leak also on my prebuilt tank. I think it was not scuffed up enough on the seams. Next time I'm building my own tank. Pro seal is not that bad to work with. Save the money for something else.