RV-10 fuel vent fittings leaking

I filled my tanks to full this week to calibrate some things and found fuel leaking out the fuel vent. At first I thought this was an overflow situation down the vent line, but after some taxi testing and a few days of drips, the fuel level is low enough that the end of the vent is dry and above the fuel level.

There is no fuel outside the tank anywhere, just a steady slow drip out the vent line. The only thing I can figure it must be is a loose or leaking fitting inside the tank, where the vent tubing connects to the blue AN fitting that passes through the tank wall.

Other than “don’t fill the tanks above 20 gallons and park the plane”, does anyone have any advice how to fix this? I don’t see any way to get a wrench in there to tighten that fitting. And how dangerous is this? If this came loose in flight, all the gas above that line would dribble out, although I guess some suction through the vent as gas is burned would slow the drip rate.

My tanks were quick build tanks, for what that’s worth.

Thanks in advance!

Vent

Yes, this was an issue. The nut on the back side of the vent fitting probably wasn’t tightened. I found this out before I installed my fuel senders. I was able to make a wrench that was able to reach through the hole and tightened the fitting..

I think a really motivated, diligent, and patient person could tighten the fitting on the inside of the tank through the hole where the sender mounts. You'd need to get two wrenches through that hole and hold the AN-832 while you tighten the -818.

Yes

It is doable but it is tedious and takes patience.

Only one place

The only thing I can figure it must be is a loose or leaking fitting inside the tank, where the vent tubing connects to the blue AN fitting that passes through the tank wall.

Click to expand...

I can't think of another spot where fuel would enter the vent line.
I am not sure how quick builds are completed but all of my inside tank connections are sealed shut with pro seal.
If this is indeed a leak on the inside connection, you'll have no choice but to cut an access plate and tighten the nut. I would pro seal all those connections to ensure none will ever leak again.
There is not a lot of room between the wing an fuselage and I know you'll hate the idea of removing the wing but it may be necessary to allow proper access to do the repair. Alternatively you could remove the tank but removing the wing might be less trouble.

Was worried about that too.

I just finished my tanks. After torquing that fitting inside the tank, I asked myself how can I keep that fitting from ever backing off? Slathered it with proseal to eliminate the potential for leaking or it ever coming free.

If they are quick built wings call Vans. I had the issue and they made me the tool and sent it. There is another thread on this with a lot of details.
I continued with my test flights with it leaking, just plugged it on the ground.

Thanks everybody! I have very little interest in taking the wings off at this point. I'm not even a fan of removing the fuel sender, cleaning up all the proseal, reaching that nut, and pro-sealing the sender back on again. What a pain.

Not to mention the week to get proseal from Van's or Aircraft Spruce, and 72 hours for it to harden....

I will call builder support tomorrow, since they are quickbuild wings. A bent box wrench from them sounds like a great idea.

Thanks again!

I just spoke to Sterling and he emailed me the photo below, of a wrench with a handle that someone fabricated to fix this problem. Does anyone recognize this wrench or have it on them? Can I borrow it? Of course I will pay for shipping both ways! Thanks!

Another -10 vent fitting fix

It seems there have been a few -10 quick build tanks with this issue. I recently did a re-seal for a gentleman who tried the bent wrench solution to no avail. I had him remove the tank and I cut an access hole in the I/B bay. The vent line was tight, had no encapsulating sealant on it, and after removing the "B" nut, i found a poorly completed flare that was not capable of seating. This aircraft was in phase 1 and had leaked out the vent from the first fueling. I couldn't re-flare, and tube removal is near impossible, so I installed a flare seal, tightened and encapsulated the entire fitting as I do with all internal line connections. As you can see in the picture, this line was never encapsulated. This was a quick repair, but still required tank removal..fortunately it was stll unpainted.