Fuel Tank Leaks

[fastj22]

Has anyone out there ever experienced leaking at the fuel vent fitting or the fitting at the back wall of the fuel tank? These fittings are located very close to walks of the fuel tank and look like a real challenge to replace. My feeling is to leave them alone, but if they are prone to leaking I may replace them now while the tank is out.

Don Bowen
N49YX

No. I think the problem is primarily where the fittings are immersed in fuel (or mogas) and corrode enough to not allow any removal or tightening. That's what happened when I tried to remove my fuel sender. It spun the fitting. Its a bad design. There simply isn't enough surface area in the molded fitting to handle the torque of removing a corroded fitting. If Sonex simply tripled the size of the flange on the fitting when its molded into the tank, it wouldn't be an issue. I love the idea of a rotomolded tank. The safety of it in a crash is very good. Sonex's design of the fittings is poor. In fact, they should just leave them out and include the oops fittings in the kit as a standard method.

[radfordc]

The continuing adventures with fuel tank fittings.....

I spent most of the weekend with my Dremmel tool working on removing the material on the inside of the tank.

This was a lot more work than I would have imagined.

This job has been a real pain in the rear.

Wow, what a nightmare. Makes me glad that I was able to repair all the fittings in my tank in about 30 minutes.

[Waiex 49]

This has been one of those jobs where the airplane has been arguing with me the whole way. It has been something of a nightmare. I believe the Sonex tank fittings to be of substandard grade and the instructions for their "fix" are awful. Just another day living the dream in paradise!

I do work slowly as I spent too many years mechanicing against the time clock. Also, I take it slow to do quality work and avoid costly mistakes.

30 minutes?? It will take me more time than than that just to clean all the junk and debris out of the tank!

Fly safe! (And often)

Don

[rizzz]

This has been one of those jobs where the airplane has been arguing with me the whole way. It has been something of a nightmare. I believe the Sonex tank fittings to be of substandard grade and the instructions for their "fix" are awful. Just another day living the dream in paradise!

I do work slowly as I spent too many years mechanicing against the time clock. Also, I take it slow to do quality work and avoid costly mistakes.

30 minutes?? It will take me more time than than that just to clean all the junk and debris out of the tank!

Fly safe! (And often)

Don

I'm not looking forward to the day I will have to do mine.
Given the amount of people that have had to do the Oops repair, I guess it's not a matter of if, it's a matter of when...

[wlarson861]

I did the ProSeal repair that John Davis did on his. American Sonex Association web site used to have the details. Tried to do the oops fitting but screwed up the hole so it was over-sized and the fitting wouldn't work

[Bruce593SX]

I know it wasn't that exact product, but be very careful: http://www.ntsb.gov/_layouts/ntsb.aviat ... 050&akey=1

The q&a on spruce website says not recommended for plastic tanks

[wlarson861]

I know it wasn't that exact product, but be very careful: http://www.ntsb.gov/_layouts/ntsb.aviat ... 050&akey=1

The q&a on spruce website says not recommended for plastic tanks

There is nothing similar with that repair and the sloshing compound in the crashed aircraft. I used an brass reducer fitting that was threaded into an aluminum plate and into the tank. The area around the fuel line opening in the tank was coated with Pro-seal and the plate was attached with pk screws while the sealer set up. The original finger strainer was threaded into the reducer fitting and the fuel line installed as per plans. No sealer went into the tank so there is nothing to clog the strainer. I have been leak free for more than two years.

[wlarson861]

here are the pictures of the repair.
https://picasaweb.google.com/1048255426 ... directlink

[kevinh]

Bill - that seems to be a great fix! If I ever have this problem, I'll do something similar...

[Waiex 49]

I installed the oops fittings in my tank yesterday and thought I would share with the group.

I was very fortunate that a member of this forum lent me his custom made tools for smoothing (sanding) the inside surfaces of the tank. i had to remove almost all of the plastic mound that was molded around the fittings to get a smooth surface with the same diameter as the o-rings. Pretty much all that was left was the wall thickness of the tank. This gave me a good mating surface for the o-rings, but the fittings sit lower than others have done and more of the fittings stick out. I don't think this is a problem. If I run into any clearance issues I could always Dremmel down the fittings as needed.

I ended up not using the outer o-rings. When I tightened the nuts the o-rings didn't take well to the rotation and they would not stay in place. I had been warned about this by another member of this forum. He sent me some very nice thin fiber washers to use under the nuts. I used a little bit of Permatex #1 sealant and installed the washers and the nuts. Without the outer o-ring the nuts will tighten down properly. The inner o-ring is providing the seal, not the outer o-ring. The inner o-ring is not subjected to rotation and compresses down nicely to form the seal. I did use some locktite to keep the nuts from backing off.

I'll buy some brass plugs to put in the fittings so I can do a proper leak test. I'll put in a couple gallons of gas into the tank and let it sit for a few weeks while I finish wiring the plane.

I am damn glad to have finished this repair. This has been a total pain in the ass.

Sonex should be ashamed for selling tanks with such awful fittings. They offer a "fix" but don't address the root cause of the problem. This is really low class. They should address this problem and start selling a decent fuel tank.

I hope to get back in the air this summer. Probably too late to make Rio Linda, but I'll be there as a pedestrian.

My thanks to all who have helped and offered advice!

Don Bowen
N49YX