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Fuel tank leak

rvaitor87

Well Known Member
Greetings all:

I would like to share an experience with you that hopefully will help others with the same problem.

I have a -3 which my father and I built back in the 90's, and we used proseal when assembling the tanks.

Fast forward to 2 months ago, when I noticed that when I went to fly, the fuel level in the tanks was very low, and in some cases, gone. :eek: first thought was that the fuel thief gnome had been to visit, but quickly ruled that out. I use my inspection video camera with the long snake on it and checked behind the tanks, dry no discoloration. Also, no weeping rivets. After not flying for over a month, and banging an indentation in the wall with my head, a small light went on. I remembered that several months earlier I had replaced the fuel test ports with ones off of my -4 project, because I had noticed a little seepage from one of them.

Could it be that simple? :confused: I removed the ports and replaced them with brass plugs. No leaks. I examined the ports and found that the little "O" rings were dry rotted, thus causing the leak. New ports ordered.

Lesson learned, even though they were never exposed to fuel, they still went bad. I should have just ordered a new set and been done with it, but because both tanks were affected, that thought never occurred to me. And it would have also helped if I would have entered into my log book the fact that I replaced them, a lot of the aggravation would have been avoided.

Feel free to chime in all you want, it was a dumb mistake on my part, but hopefully it will help someone else with a similar problem, or any other for that matter.

Time to go flying! :D
 
If you haven’t thrown away those older drain valves, don’t. It’s easy to just replace the little o-ring in the valve. If you do that, you’ll have a spare to carry with you in case you get a drippper when you’re on the road.
 
I had a bad O-ring on a (CAV-110) spring-loaded drain valve on one wing tank, but knew it because of the blue fuel staining on the hangar floor beneath it. I replaced it (and the other two as well) with new ones and that fixed the leak. I'm surprised that you could lose that much fuel from the valve without visible evidence. I must be missing something. Where was the fuel going that you couldn't see it anywhere?
 
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To echo what Scott said I actually bought one extra quick drain and a few orings. When one leaks I simply install the new quick drain, you can do this quick enough to lose almost no fuel. Then I clean the leaky one and put a new oring on it ready for the next time. Only have had to do it twice so far. :)
 
To echo what Scott said I actually bought one extra quick drain and a few orings. When one leaks I simply install the new quick drain, you can do this quick enough to lose almost no fuel. Then I clean the leaky one and put a new oring on it ready for the next time. Only have had to do it twice so far. :)

What's your technique for changing those little buggers? Mine tends to result in a fair amount of fuel down my arm and on the ground. Last time I ran the tank as low as I could, then just pulled the drain and emptied the tank into a bucket.
 
What's your technique for changing those little buggers? Mine tends to result in a fair amount of fuel down my arm and on the ground. Last time I ran the tank as low as I could, then just pulled the drain and emptied the tank into a bucket.

I put some latex gloves on first. I make sure I get the new quick drain ready with thread sealant and then put it within reach of the one in the fuel tank. After taping off the fuel vent and fuel cap I unthread the old quick drain from the tank. As soon as it comes off I put a gloved finger over the hole as quickly as I can. With my other hand I grab the new one and quickly get it in the hole and start threading. A bit of fuel comes out but only an ounce or two. It does get on my gloves a little bit but not on my arms. Works great!

P.S. I usually have a little bucket on the ground to catch any of the fuel. Also, for the love of whatever you believe in make sure the tape comes off the vent! That is really the main reason I tape the cap too, a reminder that the system has been taped.
 
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