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Putting gas in tanks

s10sakota

s10sakota

Well Known Member
Has anyone leaked checked their fuel tanks by actually putting fuel in them?

I'm thinking that the most likely place for the tanks to leak would be the rear of the tank.

So why not put the tank on a table with the leading edge facing up, and put about a gallon of fuel in the tank? That should be enough for 1/2 to an inch of fuel on the bottom.

Has anyone done this? Is there any reason NOT to do this? I just don't trust the balloon test. There's too many places for air to leak out like the fuel caps and the balloon itself.

I would hate to 'think' the test is good, bolt the tanks on, paint the wings, and the find out there is a small leak somewhere!

Thoughts??
 
Check it with air

The leak could be at any rivet. Put the fuel cap on and seal the cap with duct tape to eliminate the cap from the test. Use the drain to put a very small amount of air pressure in the tank. If your using a air tank let the pressure in the tank out until it is below 20 psi you are only going to put a enough air in to inflate the balloon. By using a balloon you can make sure you don't put to much in, if you put too much in the balloon will burst. If there is a leak it is going to deflate pretty quick. The change in the temp will cause the balloon to slowly deflate and inflate over time. Use soapy water and a spray bottle to check around all areas that might leak.
 
s10sakota said:
So why not put the tank on a table with the leading edge facing up, and put about a gallon of fuel in the tank? That should be enough for 1/2 to an inch of fuel on the bottom.
Click to expand...

I did the balloon test and it passed. However, about that time there were a series of posts on the forum regarding tank leaks and the onerous process of fixing them. So I did the six sigma test. I put the wings on a big very well padded bench and filled to capacity with avgas. No leaks.

Another major motivation was the hassle of removing the tanks (should that be necessary) after you have them painted.
 
I did the balloon test and sprayed the tank with soapy water. The only leaks I could find were at the balloon itself...



...and the tank drain (which has the bicycle pump fitting in it). Obviously the fitting is going to come out, but I'm wondering if there is any type of sealant I should put on the threads of the actual drain fitting to prevent leaks there?

 
Sorry for a dumb add-on question, but when the airplane gets painted, does the fuel drain come out or is it just taped over for paint? If it has to come out again, I won't seal it up now! :D
 
s10sakota said:
Has anyone leaked checked their fuel tanks by actually putting fuel in them?

I'm thinking that the most likely place for the tanks to leak would be the rear of the tank.

So why not put the tank on a table with the leading edge facing up, and put about a gallon of fuel in the tank? That should be enough for 1/2 to an inch of fuel on the bottom.

Has anyone done this? Is there any reason NOT to do this? I just don't trust the balloon test. There's too many places for air to leak out like the fuel caps and the balloon itself.

I would hate to 'think' the test is good, bolt the tanks on, paint the wings, and the find out there is a small leak somewhere!

Thoughts??
Click to expand...

Mark, that's exactly what I did. With three airplanes. I put 6 gallons of 100LL in each tank then sat them on the rear baffle for a day or so. Then I sat them on one end for a day, and so on. I also sat them in the cradle with the leading edge down for a day. This is the only reliable method to truly guarantee leak-free tanks, in my opinion. I think air molecules are larger than fuel molecules so in theory you might pass the pressure test and still have a leak with fuel.
 
Glad I'm not alone Pat! I'm going to do the exact same thing tomorrow. I just need to get the Permatex-2 to install the fuel drain!
 
s10sakota said:
Sorry for a dumb add-on question, but when the airplane gets painted, does the fuel drain come out or is it just taped over for paint? If it has to come out again, I won't seal it up now! :D
Click to expand...

Mark, you should not seal the fuel drain now. It will be removed a few times prior to paint; for example, if you test your tanks with fuel and then have to drain it. In any case, just a little Permatex #2 is all you need. You'll want to be able to remove it for maintenance, like if you need to change the O-ring some day.
 
Fuel lube

I've used Fuel Lube on my drains with no leaks. I also keep a spare drain valve in my tool bag. You will need to replace the small o-ring in the future and having a spare drain vavle in really nice.
 
I used fuel

I both tested with air and fuel. A friend who had problems with his tanks, found that even though he had no leaks using air or sprayed water he still had fuel wicking around some of the rivets. so I filled the tank with car fuel and let it sit for a day, and then looked for leaks. Sure enough I had a couple. Then I transferred the fuel to the next tank. No problems with that one. Then I put the fuel in my car.

Cheers

Jim
 
That's exactly what I'm doing! I put fuel in one of the tanks last night. I haven't looked at it today yet, but hopefully there's no leaks. I have the leading edge facing up so I'm testing the back of the tank now. If no leaks, then I'll let the tank sit on it's two ends for a day each. Finally, I'll put it in the cradle and test the front. Then I'll dump the gas into the other tank and do it all over. Then I'll burn the gas in my car :D
 
Lookin' good so far! No leaks anywhere along the rear baffle, and no leaks on the outboard end!! Now I'll flip the tank over and check the inboard end...

feelin' good so far :D
 
Oh well.......

Did the balloon test and tested fine.
Today I put 2 GAL of car gas in it and I had one rivet leaking. Lucky me it's on the bottom and I think I'll just seal in a pop rivet.

The other tank did never check out good and I put gas in it after I just couldn't find the leak. The gas came running right out of the rear baffle. Got that fixed now and will be ready for testing next week.

Yeap! The gas will tell the truth!!!
 
I'll do it right :)

Had the tank sitting for two days now and rotated it like a rotisserie chicken.
Found two more rivets and a food long baffle seam leaking. What a mess.
I used almost the whole can of pro-seal on one tank and still didn't get it right.

So after getting over that frustration I will tackle the cutout for the baffle on two places and seal it up on the inside.
 
The PDF is there at cafefoundation.org , click "research" tab, then "reports" down the right side. It is in the list.
 
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BillL said:
The PDF is there at cafefoundation.org , click "research" tab, then "reports" down the right side. It is in the list.
Click to expand...

It is titled "Fuel Handling Safety" and worth reading.

Fuel can be handled safely but one needs to be aware of the hazards of doing so. The key is managing static electricity and the report explains how to do it.

PS The balloon test is valid. My tanks passed and now have fuel in them all the way to the flow divider, no leaks so far. You can do a tank leak check with the balloon procedure or air pressure and soapy water with confidence so why mess around with fuel before you need to.
 
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fuel handleing

BillL said:
The PDF is there at cafefoundation.org , click "research" tab, then "reports" down the right side. It is in the list.
Click to expand...

I read it. Pretty scary. Makes me nervous about filling my lawnmower much less anything bigger.
I can attest to the volatility of gas. Long ago I worked for a transportation agency. One day a driver was fueling with a cigarette. I asked her to put it out. She quipped about how nothing would happen because she does it all the time and showed me how safe it was by flicking a lighter next to the tank fuel hole. Guess what happened. She took off running. Thankfully the tank was completely full to the neck and only the vapor by the neck and the fuel on the ground where she threw the nozzle caught fire. I went for the extinguisher and blasted everything in sight. That could have been a really bad day for a lot of people. And they didn't fire the idiot!
That's the first time in 25 years I've retold that story.

I think about that day a lot. Every time I fill up a vehicle. It makes me even more nervous up here in the mountains because everything generates static. You hear the crackle all the time.
 
Fuel in tanks

I leak checked mine with a balloon but it kept deflating. I fixed all the leaks I could find with soapy water. I put some fuel in it, capped it off and put it in the sun and within 20 minutes I starting seeing fuel weeping from quite a few rivets in the skin to baffle area. I now pass the balloon test and the fuel test.

s10sakota said:
Has anyone leaked checked their fuel tanks by actually putting fuel in them?

I'm thinking that the most likely place for the tanks to leak would be the rear of the tank.

So why not put the tank on a table with the leading edge facing up, and put about a gallon of fuel in the tank? That should be enough for 1/2 to an inch of fuel on the bottom.

Has anyone done this? Is there any reason NOT to do this? I just don't trust the balloon test. There's too many places for air to leak out like the fuel caps and the balloon itself.

I would hate to 'think' the test is good, bolt the tanks on, paint the wings, and the find out there is a small leak somewhere!

Thoughts??
Click to expand...
 
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