Fuel tank leak

Brian Diehl · May 17, 2015, 10:12:27 AM

Found the source of the leak. It looks like some sort of electrolysis was happening to two spots on the bottom of the tank. The worse spot had developed a pretty good sized pin hole leak. I opened up the spot with my screw driver. So, what do people normally do for this type of leak? Does one cut out the bad spot and weld in a new piece of aluminum or does one simply weld on a patch?

Jon · May 17, 2015, 11:41:05 AM

Welding on a fuel tank can get pretty exciting. Not the smartest thing to do.

muldoonman · May 17, 2015, 11:53:07 AM

I would put a patch on bottom corner or whole bottom. A competent welding shop should have no problem if it's aluminum. Tig or Mig. Even some radiator shops can do it. Just clean (steam) tank first. Have done many of fuel and air tanks the same way. Test with air and Low Pressure. 5 to 10 lbs. only. Looks like it's been rubbing on something by pic number 3. Where are you located??

Jon · May 17, 2015, 11:56:48 AM

When I worked in a junk yard we were never allowed to get a welder or torch near a tank, no matter how dry it was or how long the vehicle sat in a pasture.

We were only allowed to remove then by cutting the straps with an axe. Too many stories about tanks, (dry old ones) blowing up.

digesterman · May 17, 2015, 12:06:40 PM

Aluminum will absorb fuel, one reason used aluminum is hard to weld, there is a procedure that calls for using steam to sweat the fuel out. I'm sure if you Bing it you will find something on it.

muldoonman · May 17, 2015, 12:11:30 PM

Jon i understand about the fuel dangers and hope everybody else does also. Steam it out and you won't have any water vapor to dry out later. Most shops will also run nitrogen inside under low pressure while welding if still unsure. I wouldn't be bothered if I was doing it. Of course I have been welding for over 40 years and still have all explosion meters and certifications including aircraft. Welded up a lot of alloy landing gears that had cracks from hammering the ground on hard landings. Just make sure you are dealing with somebody insured and knows what they are doing. Just another day in the park. No problems with this simple job. Just expect to pay that expert.

muldoonman · May 17, 2015, 12:15:20 PM

Still have a mobile Lincoln Ranger Gas Welder out in the barn with a Hi Freq unit, trailer mounted just for this type of welding. Hadn't started the puppy in a while as I've gotten lazy and rich from welding fuel tanks. LOL.

Lin · May 17, 2015, 12:25:53 PM

I suppose that one question I would have is about how many other spots there are that are just waiting to open up and start leaking. If I were going to the trouble of taking the tank to a welder, I would consider putting a whole bottom plate on it.

I have repaired gas tanks using JB Weld that seemed to last indefinitely though.

muldoonman · May 17, 2015, 12:37:27 PM

I would do the whole bottom as procedure would be the same and lay it over the existing one. Good welding shop would know the properties on the aluminum as there are different grades of the metal and alloy's. Different filler rods also. Don't take it to a amateur. Stay away from the JB weld, or I would as that's a lot of static pressure from a hundred or so gallons of diesel fuel.

luvrbus · May 17, 2015, 01:15:04 PM

Could be cheaper to build a new tank from stainless,I removed the auxiliary tank from my MCI and patched it washed the inside

I did it like most oil field welders do ran a pipe from the exhaust on the car to the inside the tank for 10 minutes then welded the sucker no oxygen in the tank no boom OHSA approved I don't think so but it works

Consider yourself lucky you have a tank that can be patched the newer Prevost have a plastic tank no patching those big $$$$ suckers

Scott & Heather · May 17, 2015, 01:21:25 PM

It's a diesel tank. If it were rinsed, it wouldn't blow up on you. Not sure it's necessary to say "not the smartest thing to do". If it were a gasoline tank, the impetus to rinse the tank well would be even more important, but as for the diesel fuel soaking into the aluminum, I would definitely research proper cleaning at least for that particular spot/area. But shouldn't be a dramatically dangerous or difficult job for someone good with aluminum.

Brian Diehl · May 17, 2015, 01:45:28 PM

Thanks for all the feedback everyone.

Muldooonman - I am in Minnesota - south and west of Minneapolis by about 1h 30m. So - now I need to find me someone in the area who is comfortable (and trained/experienced) in this type of repair. I don't intend to do it myself since I don't weld aluminum.

As far as the rest of the bottom of the tank it is in excellent shape. Whatever caused this problem was not "rubbing". It was some sort of galvanic corrosion as the aluminum was clearly "eaten" away in this spot. Interestingly, it was corroded from the outside in.

Clifford - I'm definitely glad this is an aluminum tank and not plastic!

muldoonman · May 17, 2015, 01:58:53 PM

Thanks for the location Brian. Started to say if you where down Texas way I would do it for you. Replace the whole bottom with a overlay. Good luck.

eagle19952 · May 17, 2015, 06:57:02 PM

Scott B. don't be fooled diesel vapor is still present after "rinsing".... You would actually be safer to weld a steel tank that was full of diesel than not.
I am like clifford, oilfield gitterdun, "or we'll get someone who will"... I won't go into detail, but I'm still here to talk about it LOL

luvrbus · May 17, 2015, 07:27:49 PM

When I working for Tennessee Gas all our final tie in on the natural gas lines were done with natural gas flowing through the pipe if you had no flame you waited till the gas would flame before welding. lol it takes you a while to go around a 36 in pipe.

Has nothing to with welding a fuel tank but it can get interesting if the fire goes out while you are welding, so welding on a fuel tank never worried me I have repaired many of storage tanks before full of diesel by welding, they never drain those tanks to repair a leak fwiw