Leaking fuel tank

Last weekend I opened the hangar door to find a, previously full, 19 gallon tank dry. It had drained within a period of two weeks while I had stopped up ears.

As shown in the picture, the trouble area seemed to be the two bottom screws of the access plate that had been sealed with a proseal type material.

I experimented with putting fuel in the tank to see if I could see for sure just where the fuel was leaving but all I could get was a general wetness.

I ordered some #8 O-ring screws from McMaster-Carr and replaced those two bottom screws only after cleaning away the sealant. I didn't mess with the others on the "if it ain't broke" theory. Maybe I will regret that.

After I fueled up and observed for a few hours I decided the plane was airworthy.

I may not get much sympathy from the Minnesotans but it has been cold here. Not too cold to fly or anything but when the low is around 10 and the high around freezing I just hesitate to start the engine without any sort of preheating. We just aren't well prepared for cold weather here in the Southwest.

So today it was much better with a high around 60 degrees and just a touch of cirrus to moderate the sun rays. I flew over to the other side of the Guadalupes to observe some new-to-me WWII practice bomb targets. One of them was unusual in that it actually had good sized craters, unlike what the normal practice bombs created. Then I flew a bit along the west boundary of Guadalupe Mountains National Park to see if I could pick out where some cows were getting in. Then back over the Guads to fly some canyons, thence to the blue/green colored Black River, near Washington Ranch and the gypsum sink holes near there.

Do you all have any idea how privileged we are to live in this country and have the airplanes that allow us to see what others can't?

My plane seems okay again and I sure enjoyed it today!

Another Try

Well, I have learned to leave my airplane with the right fuel tank close to empty, because when I come back it is going to be completely empty; to the last drop. Previous remedial efforts have failed so I tried again today.

With the help of George, I did a soap test today. First we couldn't find anything but after a while a leak showed up where one would expect when every drop drains out, at the very back bottom corner.

As I previously reported, the sealant in this area is only slightly more viscous than peanut butter. Very odd. It seems to get firmer as one gets further from the leak site and is completely normal several feet away. It is as if the fuel leak has softened the sealant, but isn't it a fuel sealant?


This photo is when I started removing the soft sealant in the area of the leak. This is a quickbuild tank, but I think I would have surely remembered if the sealant had been this way at the beginning.



Here I am in the process of cleaning to apply new sealant. After a bit of scraping with the Popsicle stick the remaining sealant was cleaned off by merely wiping with a paper towel.


I replaced the soft stuff with new sealant on the outside. I'm aware this may not do the job. If it doesn't work I'll go inside the tank. I'm getting real fast at pulling that tank!

Observation

Larry:

Slightly off topic but I'll make one observation. While you have the tank off you might consider replacing those Phillips head screws with the socket type. If you ever have to remove the fuel sender with the tank in place, these will be much easier to unscrew than the Phillips style. You can use one of those little ratchet type wrenches you can buy at Sears.

Chris

Sealing tanks

Sorry to hear about tank leak. One of the processes we have used on small corner leaks is to thin the sealant (one of the pro-seal variants) down to a workable viscosity for a large (horse) sringe, clean the area throughly, apply the thinned sealant via the sringe while negatively pressurizing the tank allowing the sealant to be drawn into the leak. The process is slow, tedious and somewhat frustating but does work. Beats opening up the tank.


Alternatively, if you must open the tank, just cut a 4? ? 5? hole in the rear baffle of the appropriate bay, real seal through the hole, cut a stiffening ring and, cover plate and seal up. (I just opened and resealed 6 gas bays on an RV-4.) I used Murphy's sealed pop rivets they sell for their float kits.

n5lp said:

I may not get much sympathy from the Minnesotans but it has been cold here. Not too cold to fly or anything but when the low is around 10 and the high around freezing I just hesitate to start the engine without any sort of preheating. We just aren't well prepared for cold weather here in the Southwest.

Click to expand...

Yikes. you'll get sympathy from me! Feeling the cold is a matter of the body responding to what it's used to. In another month, the 20 degrees that made me shiver in November will feel like T-shirt weather. So the opposite is certainly true.

Frankly, Larry, I'd rather have it be -10 than have to mess with a leaky fuel tank. You've earned your stripes this weekend!

Bob Collins said:

Yikes. you'll get sympathy from me! Feeling the cold is a matter of the body responding to what it's used to. In another month, the 20 degrees that made me shiver in November will feel like T-shirt weather. So the opposite is certainly true.

Frankly, Larry, I'd rather have it be -10 than have to mess with a leaky fuel tank. You've earned your stripes this weekend!

Click to expand...

Bob, the post about the cold was referring to a few weeks ago.

Hate to break it to you, but yesterday the high was 73 degrees, the wind was about 4 knots and the humidity was 10%.

I did get some flying in before removing the tank.

Frank said:

Sorry to hear about tank leak. One of the processes we have used on small corner leaks is to thin the sealant (one of the pro-seal variants) down to a workable viscosity for a large (horse) sringe, clean the area throughly, apply the thinned sealant via the sringe while negatively pressurizing the tank allowing the sealant to be drawn into the leak. The process is slow, tedious and somewhat frustating but does work. Beats opening up the tank.


Alternatively, if you must open the tank, just cut a 4? ? 5? hole in the rear baffle of the appropriate bay, real seal through the hole, cut a stiffening ring and, cover plate and seal up. (I just opened and resealed 6 gas bays on an RV-4.) I used Murphy's sealed pop rivets they sell for their float kits.

Click to expand...

If the only leak is in that corner, there's no need to cut a new hole.. Just remove the sender cover plate and get at that corner area from the existing hole. You only have to cut holes in the back baffle if it's one of the other bays that are leaking.

Tank Leaks

Take it from one who used half measures several times for a leaking tank...go inside right away to seal from there, and on the outside too. I tried outside seal and syringe injection, but neither worked for me. Removing and resealing the access plate is easy if the tank is off (which is the really hard part for me) and the fix can be made pretty easily that way. Just clean out/dig out what you can on the inside, sand, wipe with MEK and reapply liberally, then let cure and reseal the access plate. Be sure to vac out any bits/pieces of sealant before closing it up.

I don't really understand proseal, but you are right. The stuff gets like peanut butter on the outside seal if you have a leak. If sealed on the inside though, it gets hard and stays that way. Go figure.

Dennis Mitchell 6A
Fort Collins, CO