Fuel Tank Leaks

[n502pd]

I dont think the epoxy will stick to the tank. As I have not had this problem (yet?) I dont have an actual bonifide fix, but is there not some way to modify the new fitting without disturbing the inside of the tank?
Just wondering out loud, so to speak!

[radfordc]

Continuing the sad story of my efforts to replace the fuel tank fittings on my Waiex.........

For those of you who have replaced the "side" (1/8" fitting) - Any info would be greatly appreciated.

I repaired my tank leaks before there was an "oops fitting". I used common brass pipe thread reducers like this: http://acehose.com/npt-threaded-reducer ... shings.htm

I drilled out the original aluminum fitting and tapped the plastic tank using a NPT tap. For the side fitting I think I used either a 1/4 or 3/8 NPT tap, but it's not critical. Use whatever size is required for the reducer you install. Tap the plastic with just enough threads to get the reducer started. Install the new reducer by screwing it into the plastic until it is sealed tightly. Since pipe threads are tapered the more you screw in the fitting the tighter it seals. I used some thread sealing paste, but I don't think it made any difference. The reducer fitting seals against the plastic by pure brute force. I replaced both of the sight gauge fittings (upper and lower) and the main fuel outlet fitting. No leaks after about 6 years like this.

[Sonex1517]

Thanks

I was wondering if there was an alternative method. Sounds as if you found it!

Robbie

[Waiex 49]

After calming down from yesterday's fuel tank adventures I took another look at the tank.

Looking at the Sonex instructions again, I see on page 1, step 4, where they advise to remove a ridge where the fitting used to be. This step only addresses the large fitting and says nothing about the smaller fittings. The recommended tools are "sharp knife, fine file, and sandpaper.

It sure looks bigger than a "ridge" to me! It is more like a wall around the circumference of the inside of the hole. This is going to be a lot of plastic to remove, and the access is quite limited. The 1" hole doesn't look too bad of a job, but the 9/16" holes are going to be a real pain in the tail section.

Assuming I can clean up the 1" hole the oops fitting should go in fairly easy. I don't know about my chances of cleaning up the 9/16" holes. As has been mentioned before, one possible fix for these smaller holes would be to use brass NPT fittings screwed into the plastic tank from the outside. I went shopping at Lowes and Home Depot and found reducer fittings that would seem to do the job.

My next step is to go buy a set of Exacto knifes and see what kind of creative carving I can do.

Are we having fun yet??

Don

[fastj22]

Don, I remember using a dremmel with a cut off wheel. You fish the wheel and mandrel down the tank so the shaft sticks out the hole, then attach the dremel. Then you can grind down the inside face. Of course, make sure your grand children are not within ear shot. You will use every word you know as you break those little cut off wheels and have to re-start the process.

[Waiex 49]

Thanks for the tip about the cutoff wheels.

I think I'll be spending some quality time this weekend with an Exacto knife and my Dremmel tool.

I took a good look inside the tank and was amazed at all the debris inside. I tried to be careful about this, but there is no preventing all the little bits of aluminum and plastic from getting in there. I tried washing it out with a quart of gas, but most of the particles just moved around and stuck to other parts of the tank. When I finish prepping the holes for the fittings I'm going to take the tank to a coin operated car wash and give it a really good cleaning. All of these particles look ideal to clog up the fuel lines. If this job is being done with the tank installed in the aircraft be very certain you clean all the junk out of the tank. You don't want a clogged fuel line to fail your engine on take off!

You are right about protecting the ears of the young and innocent. I have been yelling some very rude things in the general direction of Wisconsin.

Don

[DCASonex]

Just a reminder, beware of using power tools around gas tanks that once had gasoline in them, makes no difference if plastic or metal tank. Even little Dremel tools and battery operated drills have commutators in their motors that make a lot of sparks. I kept blower end of large shop vac stuck in filler neck of mine while working on it, and had it blowing for about half hour before starting work. Not good idea to suck gasoline fumes into vacuum cleaner either. Work outside if you can to avoid fumes collecting.

David A.

[Waiex 49]

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. The Sonex instructions shows them removing a "ridge" of plastic with an exacto knife. I wish it was that easy. To keep the fittings in place there is quite a bit of plastic moulded around them. To find out for yourself, remove your fuel filler cap and reach inside a few inches and feel the surface around the tank vent fitting. It is like a little mountain of plastic. When you drill out the fitting, you still have to remove all of this plastic and create a flat surface for the oops fitting o-ring to seat against.

This was a lot more work than I would have imagined. This plastic is pretty tough stuff. Forget the exacto knife as shown in the instructions. The Dremmel seems the tool of choice. I attacked the plastic removal via two methods. If you grind down a cutting wheel small enough you can fit it through the hole and cut from the inside. If you snake a cutting wheel down through the tank you can connect it to your Dremmel and use the flat surface of the cutting wheel to grind away the plastic.

If you cut too fast you can heat up the plastic and it will melt and produce a lot of smoke. The plastic has a habit of melting when you cut it and then sticking back together when you remove the cutting wheel. Go slow and be patient.

Although it was not damaged or leaking I decided to remove the 3/8" NPT fitting. This gives you a 1" hole to work through and also allows you to see the backside of the other fittings. I found this very helpful.

I am fortunate that another member of this forum lent me some special custom made tools for the final smoothing down of the inside surfaces. In order for the o-rings to seat (and seal the tank from leaks) the surfaces must be flat and smooth.

I am getting ready to install the fittings and do leak tests prior to installing the tank.

I have a couple of questions:

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.

I recall reading that some felt material should be used between the fuel tank and the straps that hold it in place. My installation did not have any felt (or any other material) between the tank and the straps. The tank doesn't show any signs of wear., so I'll probably put it back together the way it came apart. Anyone have thoughts on this?

This job has been a real pain in the rear. If I were building a new plane I think I would fabricate and install some METAL wing tanks!

Don Bowen
N49YX

[Bryan Cotton]

Don,
Felt strips will cause your tank to rust. Oh wait, that was the C140 and that nightmare is over. If I was going to add some anti-chafe I would use rubber. If it is tight enough and not rubbing I would not bother. If the plans don't call for it I definitely wouldn't bother.

[Gripdana]

I put felt on my straps. I think it is optional with the molded plastic tanks. But I'm unable to check the plans now.