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Tank fitting leak

Straban

Member
I did not build my RV 8. Doing the condition inspection and noticed this. So my question is, how is this fitting sealed? Would there be proseal on the tank side? Am I looking at removing the tank? BTW, there is also a very small weep at an accessible rivet I thought I could clean up and seal without removing the tank.
 

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So my question is, how is this fitting sealed? Would there be proseal on the tank side?
Am I looking at removing the tank?
BTW, there is also a very small weep at an accessible rivet I thought I could clean up and seal without removing the tank.

The fitting should have Proseal (or equivilant) applied to it and washer inside the tank, similar under the nut on outside, followed by additional sealant beaded over everything for good measure. Most common cause of leaks around this fitting is it was twisted while the fuel line was being installed & damaged the sealant. Can't tell from the picture if a T-715 Anti-rotation bracket (or similar) had been installed inside near the forward 90 deg flop tube fitting. Be sure to install one during your repairs to prevent these leaks occurring again in the future.

The tank pretty much has to come off to gain access to that front area. You have to be able to reach around and work inside near the leading edge.

For your other small seeping issue, best lasting leak/seep repairs are done from the inside where you can apply a new layer of sealant over the affected area.
 
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That's the leading edge of the wing. So that's the air vent line.

I had a problem with that on my old tank. I fixed it by:

1) removing the fuel sender cover plate

2) Looking inside with a camera I saw that the B-nut was utterly un-screwed and floating along the air vent line.

3) So I removed the fitting, cleand the area up, got new washers and a new fitting and installed them with solid Proseal in and out.

4) Reached in and started the B-nut by hand until hand tight. This is done by lying under the plane and contorting ones self a little

5) Once hand tight I bought a wrench of the size of the B-nut, put the wrench on the nut and marked the spot where the wrench appeared in the hole for the sender. Then I asked a friend with a torch to put a 90 degree angle on the wrench handle - starting a little ways away from the mark I made on the wrench. Far enough away so that you could get enough turn to engage the nut again.

6) Got the wrench on the nut and tightened it. Had an A&P check for security.

Never leaked again....at that spot.

But the tank developed other leaks and so I had the entire tank replaced. It was nothing but trouble from Day One.
 
That does sound like a lot of trouble. I'm more inclined to remove the tank for better access, although still a lot of trouble but at least it's on the bench.
 
That does sound like a lot of trouble. I'm more inclined to remove the tank for better access, although still a lot of trouble but at least it's on the bench.

Your access will be a little better but not much. You still have to remove the sender cover plate, still have to contort your hand a little (admittedly less) to get in there and access the nut, still have to find a way to tighten it. Still may have to make a wrench to do it. If I had to do it again (I made sure that fitting was bulletproof), I'd do it the same way.

But removing the tank is also a lot of work. And then of course you have to re-install the tank. Not overwhelming because a lot of people do it that way.

But you pays your money and takes your choice.

Whatever you choose to do - best of luck.
 
That's the leading edge of the wing. So that's the air vent line.

If that's an RV8 with a flop tube, that's your fuel pickup line. The vent line is on the top side of each fuel tank.


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There is a plate that covers the nose portion of the flop tube attach point.

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Vans Service Bulletin requires the installation of safety wire and an anti rotation bracket. If yours is an older RV-8, it may or may not have that installed. If that fitting rotates, that may be the cause of your leak.

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In this picture you can see the anti rotation bracket installed. The vent line can be seen going across at the bottom of the picture with the capacitance fuel quantity sensor wiring wrapped around it.

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As mentioned before, pro-seal, pro-seal, pro-seal, is the key to a properly sealed fuel tank. Not just between the parts but also rolling the rivets in it then covering the shop head with pro-seal after they are set. It also has a long cure time (can't remember right off hand) so make sure you let your fuel tank repair set up accordingly prior to adding fuel back in otherwise you'll have to start the whole process again.

Hope this helps.
 
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That's the leading edge of the wing. So that's the air vent line.

I had a problem with that on my old tank. I fixed it by:

1) removing the fuel sender cover plate

Saville, your tank appears to have been built with vent line drilled through the spot where the optional flop tube fuel pick-up fitting is normally placed. Plans call for the vent line to be drilled farther back, about half way between the front mount bracket and access panel. Quick way to tell the difference: 1/4" tubing is vent line, 3/8" tubing is the fuel pick-up line.

I see Carlos beat me to it with excellent pictures. Note the anti-rotation bracket, very important!
 
NOT SO! If that's an RV8 with a flop tube, that's your fuel pickup line. The vent line is on the top side of each fuel tank.

I don't recall the OP saying he had a flop tube. Does he?

Do you know that he has a flop tube?

If not than it's only a POSSIBLY NOT SO!!!!!.

Though looking at the OP picture that tube does look thick. But that may just be because it's a close up.
 
Saville, your tank appears to have been built with vent line drilled through the spot where the optional flop tube fuel pick-up fitting is normally placed. Plans call for the vent line to be drilled farther back, about half way between the front mount bracket and access panel. Quick way to tell the difference: 1/4" tubing is vent line, 3/8" tubing is the fuel pick-up line.

I see Carlos beat me to it with excellent pictures. Note the anti-rotation bracket, very important!

It MAY BE that the OP has a flop tube. That wasn't actually stated so I don't know that for a fact.

Whether or not he does, the procedure to fix it would be pretty much the same.

I second your comment about the anti-rotation bracket. Very important.
 
I don't recall the OP saying he had a flop tube. Does he?

Do you know that he has a flop tube?

If not than it's only a POSSIBLY NOT SO!!!!!.

Though looking at the OP picture that tube does look thick. But that may just be because it's a close up.

I guess you missed the part where I said “if that’s an RV8 with a flop tube”
 
I guess you missed the part where I said “if that’s an RV8 with a flop tube”

Nope didn't miss it at all. That NOT SO! struck me as a pretty definitive statement saying that what I said was absolutely not true. Even with the If as the next word.

But since you meant to say Possibly not so! then fine.
 
Nope didn't miss it at all. That NOT SO! struck me as a pretty definitive statement saying that what I said was absolutely not true. Even with the If as the next word.

But since you meant to say Possibly not so! then fine.

My sincere apologies if I ruffled your feathers. Not an English major here, simply trying to help the OP.
 
My sincere apologies if I ruffled your feathers. Not an English major here, simply trying to help the OP.

Feathers weren't ruffled, and no apologies necessary. Just making sure that stand-out, bolded, exclamation-pointed definitive statements aren't left out there without actually knowing the situation. I remember how easily confused I was when first trying to learn about how all this works when I first got the plane.

Cheers
 
Thank you all for the very helpful comments and photos. I don't know if I have a flop tube or not (I suppose I'll find out when the cover plate is off), but the pickup is at the front of the tank and that is where the leak is. I did see the SB for the anti-rotation bracket and there is no indication it was completed in the log books. It's on the list to do. Thank you again for the excellent comments. Very helpful.
 
One of the reasons I think I should remove the tank is so that I can leak check any repair by putting maybe 5 gal of fuel in, standing it on end and watching it for a few days. Either way it's going to be a PITA.
 
Since you’re going to remove the tank why not leak check it like you would a new tank? Vans has the tank test kit for $10. Use a hand air pump at 2-3 psi with a balloon attached to the vent fitting so if you accidentally put too much pressure in it, the balloon will pop. If it stays inflated, you’re good. You should also use soapy water over all sides of the tank while it’s pressurized to spot leaks.
 
I just resealed one tank on my 8a to fix a couple of pinhole leaks along the rear baffle.
One easy thing I found was to place the balloon over the gas flow valve rather than the vent tube. The larger diameter of the fuel flow valve gives a better seal for the balloon.

Tom Hanaway
 
So a quick update. I removed the tank, opened it up and immediately discovered the reason for the leak. The fuel pick up through fitting was loose and had no sealant on it. So I fashioned a anti-rotation bracket sealed her up and tested it today. No leaks and tight fitting. (It is a flop tube, btw.)

The tank is on so moving forward. Quick question. The forward most inboard portion of the tank is supported by a bracket to the fuselage which clearly is meant to move. What torque should I tighten it to? And what torque should the z-bracket bolts be torqued to?

Thanks
 
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