Is it okay to cap off a wing tank sump?

From the application, that likely isn’t tapered thread, and it might not even be straight pipe thread. I wouldn’t think the odds of actually getting a seal are at all good, even if you find a cap with the correct thread. You might wind up the bladder on the inside before you came close.
 
-KLB- said:
From the application, that likely isn’t tapered thread, and it might not even be straight pipe thread. I wouldn’t think the odds of actually getting a seal are at all good, even if you find a cap with the correct thread. You might wind up the bladder on the inside before you came close.
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Yeah,, play with it until you break the drain to bag seal, then see what the next step is.
 
SkyDog58 said:
Looks like you have the ones sold by Eagle Fuel Cells for the post AD84-10-01 fuel bladders. Most likely installed under an STC that has an ICA. Look at that if you have it. Also you can call Eagle and see what they say. Some info here.
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That version can be dismantled from the outside and the o-ring replaced. The OEM version has to come out from the inside, with the tank empty. No fun at all.

A cap won't do much good. The fuel will still wick out around the cap and nut threads.
 
The plane is 30 miles away thus it took awhile to check it again (this morning).

Good news there are no drips in the bucket (or it was so slow it evaporated). In hindsight i think I pretty much had done (yesterday) what @weirdjim had suggested when I was trying to get it to stop.

The plane had sat a month, 2wks being away on vacation, 1wk me sick and 1 week of frozen/crappy hangar door problems. Up until a month ago it had been sumped on average once a week.

So it could have been some ice? Maybe where is presses up against any rubber seal it deformed a bit. Or maybe debris.

Here is a picture of the actual drain that was leaking. I saw there were outside threads. And the bottom is flush. Hence I wondered if a simple cap, maybe with rubber on the inside bottom might have been a way to quickly plug it (hand tightened only)
20190317_133043.jpg
 
Yeah, ironically I thought of gum, dut tape, etc.

If you had a sump drain stuck wide open in the middle of nowhere....how would you quickly plug it?

Here with the threads I thought there might have been a more "plumbing" like solution.
 
Sinistar said:
Here is a picture of the actual drain that was leaking. I saw there were outside threads. And the bottom is flush. Hence I wondered if a simple cap, maybe with rubber on the inside bottom might have been a way to quickly plug it (hand tightened only)
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That's the OEM version. It has to come out from the inside. The tank gets drained, the nut removed, and also usually have a hose clamp around the bladder's drain nipple to seal the valve to the bladder, which means pulling the bladder partway out of the wing to get at the clamp. Old bladders resent that and can crack and start other leaks. Big job for a simple drain valve, which is why some opt for the STC'd versions.

It will likely continue to give trouble. Water that gets into the tank rusts the guts in it which roughens the sealing surfaces, and the O-ring deteriorates with age and exposure to fuel. The STC'd version is of stainless, with only the O-ring deteriorating.

Duct tape will instantly turn gooey when fuel hits it. It's really messy. Won't work. A cap with a rubber seal to fit against the end of the threaded spud would work, but it would have to be custom-made, with a really short and shallow section of threads in it. As a former machine-shop guy, I can tell you that it will be cheaper to replace the valves than to get caps made.

Old airplanes are so much fun...
 
Okay, just to prove there is a simple "plug it until I can get fixed" solution:

  1. 1/2" Galvanized cap
  2. A small rubber stopper
  3. Cut rubber stopper so it fits inside with smooth surface towards opening
  4. Lightly hand tighten onto drain
  5. Rubber stopper fully seals against smooth bottom of fuel drain.
There was a nice brass cap which would have been more appropriate but was not in this size.

20190317_153315.jpg
20190317_153132.jpg
20190317_153242.jpg

That heavy bugger would probably kill someone if I forgot to remove it and it fell off during flight. But I'm keeping this little guy in the plane for the next time it leaks. It's like bubblegum with threads LOL :)
 
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Dan Thomas said:
That version can be dismantled from the outside and the o-ring replaced. The OEM version has to come out from the inside, with the tank empty. No fun at all.

A cap won't do much good. The fuel will still wick out around the cap and nut threads.
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Dan Thomas said:
That's the OEM version. It has to come out from the inside. The tank gets drained, the nut removed, and also usually have a hose clamp around the bladder's drain nipple to seal the valve to the bladder, which means pulling the bladder partway out of the wing to get at the clamp. Old bladders resent that and can crack and start other leaks. Big job for a simple drain valve, which is why some opt for the STC'd versions.

It will likely continue to give trouble. Water that gets into the tank rusts the guts in it which roughens the sealing surfaces, and the O-ring deteriorates with age and exposure to fuel. The STC'd version is of stainless, with only the O-ring deteriorating.

Duct tape will instantly turn gooey when fuel hits it. It's really messy. Won't work. A cap with a rubber seal to fit against the end of the threaded spud would work, but it would have to be custom-made, with a really short and shallow section of threads in it. As a former machine-shop guy, I can tell you that it will be cheaper to replace the valves than to get caps made.

Old airplanes are so much fun...
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I'm a bit confused. Can mine be fixed from the outside (your 1st post) or need to be done from the back (2nd post)?
 
Tom-D said:
go fly.
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We did fly it with the drip :). I was mainly worried about a hangar floor covered with 100LL and a spark while we're 30 miles away and no clue.

Those bladders are getting old now so I suspect we'll be back in there sooner than I'd like.
 
Sinistar said:
We did fly it with the drip :). I was mainly worried about a hangar floor covered with 100LL and a spark while we're 30 miles away and no clue.

Those bladders are getting old now so I suspect we'll be back in there sooner than I'd like.
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My bladder is getting old and sometime it drips. Wait we are talking about your fuel bladder in the plane... never mind
 
Sinistar said:
I'm a bit confused. Can mine be fixed from the outside (your 1st post) or need to be done from the back (2nd post)?
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Yours needs to be done from the inside. Much work.
 
Except if you mess up an inner tube you are out, what? ten bucks? A fuel bladder is a lot more than that. Why not make it maintainable?
 
Greg Bockelman said:
Except if you mess up an inner tube you are out, what? ten bucks? A fuel bladder is a lot more than that. Why not make it maintainable?
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They are. :) the drain you are seeing can be repaired by replacing two orings from the out side.
You'll probably loose a qt of fuel.
 
Tom-D said:
They are. :) the drain you are seeing can be repaired by replacing two orings from the out side.
You'll probably loose a qt of fuel.
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That's the STC'd Eagle-type drain. The OEM valve has to come out the hard way. If only Cessna had installed a small access panel under the wing at the drain location, shaped like that plate the OP has on his airplane. That plate he has is the modification to relocate the drain valve inboard and aft to stretch the wrinkles out of the bladder so they don't trap water. A plate like that, retained by screws and anchor nuts, would have helped a whole bunch.

More info here. See the different drains about halfway down the page: https://www.cessnaflyer.org/maintenance-tech/item/1068-step-by-step-fuel-cell-replacement.html
 
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