Fuel Tank Leak

I would like to say thanks to who ever suggested the combustible gas detector to find leaks.

I have always and a slight fuel smell when I open the canopy after the plane has sat for a while, it was very slight and I could never find anything leaking.

Well it has seemed to get worse over the last two weeks, and I had recently cleaned my fuel filter so I checked those connections and all the other connections in the cockpit. Still no leak, so I spent the $178 for the leak detector, wow amazingly sensitive device.

I ran it over all the fittings inside and nothing stood out until I put it at the corner of the floor by the wing spar. Hmm, I thought let me actually put it in the tunnel of the center section, then it really went off. So I removed the wing root fairings expecting to find a leaking sender cover plate, but they were good. I whip out the gas detector and run it round the tanks, and on the right side, if I stuck it right in the space where the tank and spar are located it really went off. looking along the bottom of the tank attach the tell tail blue stain of 100LL, at the outboard end of the tank, actually the leak thru the seam is one bay in from the outboard end of the tank, we will see where it actually is coming from after the tank come off.

This is a quick build kit from 2007, it leaked checked fine and other than one rivet on top of the left wing with a bubble I have no other signs of leaks until now. I know if I had built my tanks I would expect them to operate for more than 7 years (only two in-service). This kind of thing really chaps me! It is one thing to screw it up and have to fix it, but to pay good money for the professionals to build it and then have this well, exasperating.

Any advice on removing a painted tank would be a great help, I am thinking there is a tool or technique to help keep the paint from chipping around the screws.

If you are in the NW and need a combustible gas detector I am you guy!

Of course I just filled up after my last flight so I have nearly full tanks. The weather is clear tomorrow so I will enjoy running the thank empty so it can be removed.

Cheers.

Well that just sucks!

RVG8tor said:

I am thinking there is a tool or technique to help keep the paint from chipping around the screws.

Click to expand...

Go to Avery tools and search on "paint cutter"

Paint Cutter -- Avery Tools

I ordered the #8 --- made to cut paint around screws so you don't chip, too badly.

R.

Can you post a link, where you bought and your cost for that gas detector?

Bevan

On Amazon

Bevan said:

Can you post a link, where you bought and your cost for that gas detector?

Bevan

Click to expand...

I found this model on Amazon. I searched for "Gas Detector"

http://http://www.amazon.com/Test-Instruments-CD100A-Combustible-Detector/dp/B000HHTY7Q/ref=sr_1_1?ie=UTF8&qid=1425173754&sr=8-1&keywords=Gas+detector

Cheers

Leak Repair Plan

Well I finally pulled the tank yesterday and you can see in the photo the offending rivet that is the source of the leak. I had looked in through the filler hole before pulling and noticed the rivets here just have a dab of sealer on them, they are not totally encapsulated. I should have caught this but the tank leak checked okay and it was built as part of the QB kit.

So my thought is to make a repair that is less invasive, read that to mean no access holes. I think with a remote camera and a long tube with sealant I can glob sealant on these rivets. Then on the back after cleaning I would smother the rivet and bracket in sealant. I am thinking this would keep the gas in the tank and hopefully I will not find anymore leaks.

So does this sound like a good plan? My thought is I have already trashed the nice paint job on the screws so removing the tank is not a big deal, so if another leak developed I can do the invasive fix then.

Cheers

Leak

That looks like a Z-bracket. There is no proseal on the inside other than what was on the pop rivet when it was inserted. I prosealed my brackets. Prosealed the rivet before installing and sealed them on the outside after. Best of luck.

wirejock said:

That looks like a Z-bracket. There is no proseal on the inside other than what was on the pop rivet when it was inserted.

Click to expand...

More specifically, the rivet is not encapsulated because it is not possible to do (well if you can see them through the fuel filler I guess a few could have been).

The Z brackets are installed using blind rivets because it is a blind operation, Once the rear baffle is in place and the Z brackets are being installed, there is no access inside most of the tank.

Closed rivet

Thanks for all the input, I finally realized it was a closed rivet, so that explains why there is just a little dab of sealant on each rivet.

One idea for those building that was passed on to me yesterday, is to put a little proseal in the hole before riveting, then after the rivets are set turn the tank vertical on the aft side, then gravity will flow the extra sealant around the rivet head.

sealing my tank up today so I should be flying in a couple week. This is a good time since I have to work out of town the next two weeks.

Cheers

Mike,

FWIW, I've resealed a couple of -4 tanks' inboard ribs at the leading edge bracket by carefully cleaning the external surfaces and placing a proseal filet on all the joints & over the external heads of the rivets. The actual pressure against this external seal is incredibly low (barring a plugged vent & large temp changes), so a 3/16" x 2 bead width is a lot of holding strength against a pin hole or knife edge pressure point.

Charlie

Hi Mike,

Ignore the large hole you don't want to cut in this picture, but you can see one of my Z-Brackets and how they were sealed as an example.

Fuel tank repair by akarmy, on Flickr

Andy

Thanks, was your wing a quick build? If so, they have changed how they build the tanks. None of the rivets have proseal on the outside of the rivet heads. The good part is none of them are leaking, my leak actually seems to be between the bracket and rear baffle. I just finished slathering the base of the bracket with proseal.

This is the easiest and quickest fix and I can always get more invasive if another leak develops. I might order some more proseal and dab the tops of all the rivets while the tank is off. I am certainly not going to take the other tank off. My guess is over the years I will get more of these leaking. I guess I should have built my own wings.

Cheers

Sealant on the outside just makes you feel good and doesn't really help to keep the fuel in the tank! The idea is to stop the fuel getting out of the tank - Proseal over the head on the outside doesn't really achieve that, it really needs to be on the inside. But that is difficult as there is no access.

Might be best to remove the bracket, clean up with acetone, and remove old proseal with MEK, then reattach bracket using the correct closed end rivets and trying to get some sealant over the inside end of each rivet. A little proseal under the bracket will also help. Important to clean off the leaking fuel to get a good seal.

Pete