Fuel Tank STILL leaking...

danielhv · #1 03-31-2009, 04:12 PM

Im at a loss for words. I have 3 rivets that were leaking along the rear baffle. So I cut a hole in the baffle, looked inside with a mirror, and the bead of proseal looked beautifull... no holes, smooth, spead out when the rear baffle was riveted on... looked perfect. I smeared a nice thick fillet along the rear baffle in the compartment that had the 3 rivets leaking, make it nice and smooth, looked at it in the mirror, couldnt ask for better. Put it all back together, 3 days later, air it up, and they are STILL leaking!!!!

So I drilled them out, looked in the holes, I could see the layer of proseal between the skin and the baffle... cleaned it up some, threw some laquer thinner around to get rid of any oils in the hole and on the rivets, globbed some proseal in the hole, on the rivet, etc., and re-set them. 3 days later, still leaking. A little slower now, but still, those same 3 rivets (2 next to each other, and 1 - 2 or 3 rivets down). Im confused... I do not see where they could be leaking from. So I guess I'll try the thinning out the proseal and vacuum trick, or use some self-wicking loctite... But im curious if it'll even pull it through the holes... I mean this leak is TINY. REALLY TINY.

Thoughts? Suggestions?

robjohnson · #2 03-31-2009, 05:23 PM

How much air (psi) are you pumping in the tank? Also, are you certain the proseal is completely dry before airing it up? Is it possible that you are overpressurizing the thing and blowing the proseal out of the way before it has cured?

rwshooter · #3 03-31-2009, 05:28 PM

hey Daniel....maybe you created some sort of channel say down the baffle a ways and even tho the leaks are at those rivets the air (leak) is getting there via the channel. Ever seen a leak in the ceiling of a garage. when you look for the leak above the ceiling sometimes you will find it on the other side of house. the water traveled to above the garage and exposed itself there. Just a thought.

Robb

airguy · #4 03-31-2009, 05:31 PM

I had one pop rivet leaking on my right main tank, attaching one of the Z-brackets to the baffle, and the vacuum/loctite did the trick for me. I pulled about 30 inches of water column vacuum on the tank and put a drop on the offending rivet, it sucked about half the drop in and stopped. I let it cure 2 days and it tested good. You could have a leak path under the baffle edge coming in from somewhere several inches away and not originating right at the leaking rivet location.

rleffler · #5 03-31-2009, 05:32 PM

I agree with Rob. I think three days is too soon to pressure test a tank.

I know that I made a mistake and over pressured one of my tanks and blew out a hole through the sealant. Fortunately it was easily repaired.

I would wait at least a week, if not two, before pressure testing your tanks.

danielhv · #6 03-31-2009, 06:02 PM

I was judging the "readiness" of the proseal by what was left on the paper plate from that batch. As far as how much air.... Ive got baloons on the vent and fuel return fittings.... so I dont know how much psi per say, but im assuming that those baloons will keep me from overpressuring... I'll try the loctite trick... the unsure part is pulling a vacuum.... Not sure what the best method is... nor am I familiar with the water column method. Would pulling the baloons off, and holding a shop vac hose in the vacinity (not in, but maybe an inch above) the filler hole be enough or too much?

airguy · #7 03-31-2009, 06:17 PM

Quote:

Originally Posted by danielhv

nor am I familiar with the water column method.

Take a length of clear tubing and make a fitting to connect it with one of your fuel or vent ports. Run the tubing down about 40 or so inches, U-turn it, and back up to the top. Fill it with water HALFWAY. Make another short section of tubing and attach it to the other fuel or vent port, and get a clamp handy. Measure 15" above the water level in the clear tubing that is filled, and make a mark on the side of the tank. Suck on the other tube until the water level rises to that point, and clamp off your suction line. You now have 30" water column vacuum in your tank.

rleffler · #8 03-31-2009, 06:35 PM

To further illustrate Greg's comments, you may want to check out Mike Cencula's write up testing his tanks.

http://www.our7a.com/20070911.html

When you use a manometer, you want the water level to change 27" for 1 PSI (which is all you need). Remember, that's 27" between the two water lines, which in relality that is a 13.5" change from where you started.

My original mistake was that I ended up with 2 psi by raising the water level 27".

You can use the manometer for both positive pressure as well as a vacuum.

Like many others, I used the loctite to fix one my leaks on the rear baffle.

bob