Main tank leak

[guns68]

I have finished the repairs from from the ground loop last year. Yesterday when I put fuel in the main tank to do some engine runs I discovered a fuel leak (a 1/4 inch hairline crack) in the vicinity of the fitting where the wing tank drains into the main. I did a search of the site along with consulting the 43.13 and I am a little confused. There are some interesting leak repairs, but I am looking for something I can do that I don't need to hide from an IA (or the FAA). While reading 8-32 of the 43.13 it reads; Special sealing compounds are available and should be used in the repair of tanks. If that's the case which ones? Then again in 8-32 b. Repairs to the tank may be accomplished in accordance with the practices outlined in the chapter 4, Metal Structure, Welding and Brazing of this AC. It sounds like I should use sealents, but welding is accepted if I so choose. Am I reading that right?
What I'm hoping for is a repair I can do without having to remove the tank. If not, so be it.
Delays, delays... To quote Marvin the Martian.

[Ragwing nut]

Re: Main tank leak

there is a mil spec sealent MIL-????-B1/2. Works great, used on the outside, make sure area is dry before it is applied. Do not use sloshing sealants as they have a tendency to come loose. Not something you want in a fuel system

[astjp2]

Re: Main tank leak

Is the tank aluminum or steel? If it is steel, pull it and take it to a good radiator shop and have them solder it. They have the expertise and tools to do it correctly. If it is aluminum, pull it and take it to a good radiator shop and they can weld it. Once it is repaired, have your a&p/ia look at it and then reinstall it. Or have your a&p take it to the radiator shop so he can observe the repair. If your a&p wont accept the repair, depending on where you are located, find another one or send me the tank and I will get it repaired for you...... Tim

[Pearson]

Re: Main tank leak

I doubt if it would be approved, but I used JB Weld to repair a fuel tank leak on a car once. It is a two part epoxy glue. Maybe your IA knows of something similar that is on the approved list. I can tell you that I was amazed at how the stuff worked. There was literally a small stream of fuel draining out of the bottom of the tank. I had the JB Weld mixed up into a ball about an inch in diameter. While the fuel was steadily running out, I just pushed the mixture up into the bottom of the tank. The leak stopped instantly and didn't come back during the next three years that I owned the car. I did feather the edges of the glob out with my thumb.

The trick is whether or not you can get to where the leak is. Good luck!

[astjp2]

Re: Main tank leak

there is a mil spec sealent MIL-????-B1/2. Works great, used on the outside, make sure area is dry before it is applied. Do not use sloshing sealants as they have a tendency to come loose. Not something you want in a fuel system

Its mil.prf-8802-b2, a2, b1/2, a1/2. Works great for jet fuel I wont recommed it for avgas or mogas. I used the shit by the gallons when I was in the military on everything from F-15's to AH-64's. Tim

[freightpilot27]

Re: Main tank leak

Its a bit more work, but I recommend removing the tank and welding it. Whether it's Ternplate or aluminum, any decent A&P should be able to weld it up for you.

[Ragwing nut]

Re: Main tank leak

Its mil.prf-8802-b2, a2, b1/2, a1/2. Works great for jet fuel I wont recommed it for avgas or mogas. I used the shit by the gallons when I was in the military on everything from F-15's to AH-64's. Tim

I have never had one failure with it, as long as the area being repaired was clean. When i am forced to use a soldered tank (last one was a header tank in a J4 and an L2 wing tank), I sealed every solder joint with it before installing as they always leak eventually, no matter what you do. Since doing that i have never had to remove another steel tank after sealing it.

[8708]

Re: Main tank leak

My nose tank had a crack in the area around the neck. The IA felt it was not repairable (it looked like it had been fixed there before and other places too!). It is not the cheapest solution, but I am ordering a new tank from WagAero for $569.
Should take care of the problem and I will have a new tank.
Good luck!

[astjp2]

Re: Main tank leak

How much do you want for your old one?

[RobertP]

Re: Main tank leak

From my experience with the F22A I started with one obvious leak but finished up with a number of other smaller ones once we got the tank out and put a small amount of pressure in it ( use just enough to inflate a durex! ) so as not to expand the tank which creates fitting problems or seams leaks. I considered sealants but steered away from it in the end after a good deal of research and in any case they would not have totally solved my problem as it turned out.

IMHO only way to do it is "bite the bullet" & get the tank out test it and weld it properly as it is never worth risking AV Gas fumes in the cabin and at least that way you can sleep at night once it has been repaired / re fitted.

Best of luck because it is very frustrating at any time but I guess especially so in your case.

[guns68]

Re: Main tank leak

thanks for all the suggestions! I just can't win. I went out to the plane this evening to drain all the fuel and take a closer look at the crack and the surrounding area. When I removed the glass gascolator bowl it slipped and shattered on the hangar floor. I think my plane hates me.

[astjp2]

Re: Main tank leak

thanks for all the suggestions! I just can't win. I went out to the plane this evening to drain all the fuel and take a closer look at the crack and the surrounding area. When I removed the glass gascolator bowl it slipped and shattered on the hangar floor. I think my plane hates me.

Spruce has an ACS one that I used for mine, my glass one was long gone when I bought my airplane. Tim

http://www.aircraftspruce.com/catalog/appages/acsgascolator.php

This one is even better!

http://www.aircraftspruce.com/catalog/appages/gascolators1.php

[VictorBravo]

Re: Main tank leak

Before removing the tank, I'd take a chance on the JB Weld method and just see if that works. If it works, the repair cost you $5 and not taking the tank out. If it doesn't work it cost you $5 extra and you still have to take the tank out. If you have access to the MIL spec sealant that was mentioned, that would of course be even better.

The idea is to invest an hour of your time doing it with sealant first, then test it to see if it solved the problem. Maybe yes, maybe no, but it's cheap and fast and you may get lucky.

What I'd suggest is to make up a "finger patch" that extends an inch around the crack. Make it out of whatever the same material as the tank (Alum, Terne Plate, steel, etc). Sand the tank surface thoroughly with 80 grit paper, make sure it is completely clean shiny metal. Same for the finger patch.

Form the patch to the contour of the tank so it fits well. Glue the patch on with the JB or MIL sealant glue. After it is all dry and fully cured then fill the tank with fuel and have a close look.

The idea of the finger patch is to have a structural "doubler" that prevents any movement or widening at the crack location.This should give you the best possible "glue repair". If this method doesn't work then you have to remove the tank and have it welded or soldered as mentioned previously.

I understand that some people are a little apprehensive about a glue type repair on something so critical as the fuel tank. This is indeed something you have to pay attention to. But your spars are also glued together and you trust them. You can tape a piece of napkin onto the bottom of the tank as a tell-tale. If avgas leaks out of that crack you will see a blue stain on the napkin LONG before it becomes a safety problem.

[Mark Julicher]

Re: Main tank leak

I have little doubt that JB weld will work. I have seen it several times. However, be advised your insurance is probably void the moment you start using non-approved repair methods.

[Robert Lees]

Re: Main tank leak

I have little doubt that JB weld will work.

That could be read two ways!