1939 Allis Chalmers B gas tank fix? Cracked steel on bottom

[RichLo]

This is a working tractor... needs to fixed before the acreage needs mowing again.

This gas tank is impossible to find so a simple replacement is out of the question unless somebody on here can find one somehow.

This has been working tractor with me for about 10 years now and it started leaking this spring and got worse fast so I took it off tonight to find a previous owner already repaired it. Apparently that stuff wasn't too bad for an external goo fix.

I WILL NOT do an internal sludge-and-dry fix. I have fought that stuff from previous owners for years on other stuff and will not do that to anything I own!

What is the best way to fix this? Would a machine/welding shop even touch this for brazing?

My best option at this point is clean it up really good to get down to bare metal and then 2-part epoxy it unless somebody else has any better ideas???

 

[Carlaisle]

I did not know that gas tank was so rare. If it was my problem to fix, I would weld it and then clean up the inside and line it. Failing that, can you retrofit a more readily available tank? The WD tank seems to be available and has similar lines but it is a little bit bigger and so may not fit in a convenient or agreeable manner.

 

[Erik the Awful]

Years ago one of my coworkers was tasked with welding the fuel tank on an air start cart which ran on JP8 jet fuel (high grade kerosene with a low flash point). He put it out on the industrial drain with a hose jammed down into the bottom and let the water run for a full 24 hours. Then he left it nearly full of water while he welded the crack. He had no issues, but you'll want to be careful mixing welding with water.

 

[pressureangle]

If you can't tolerate even a high quality lining- these guys specialize in small tanks;

Fix Motorcycle Gas Tank, Rust Removal, Lining, Sealing, Fuel tank

Fix your motorcycle gas tank permanently. Gas tank rust removal, repair, cleaning, lining, sealing. America's #1 Gas tank repair and restoration service since 2002...

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then your best bet is to cut the bottom out and have good metal welded in by a competent metalworking body shop. The problem with new and repaired is that you can't ever completely keep water out and it will eventually rust again. Old tractors are the worst.

 

[Hipster]

What the rest of the inside look like might be a determining factor. If there are other areas just short of perforation, it's only a matter of time. I've never heard of this professional process linked to but dealing with cycles I have used many over the counter gas tank coating products. It always ends the same, peeling and clogging up carbs. it's also been my experience that smear on epoxy type products might keep it from leaking until the gas penetrates it and that the metal has continued to deteriorate and the bad spot is even larger. Best thing to do welding a tank is to tape off the openings and fill it full of shielding gas. It displaces the fuel fumes and cuts down on the bomb/shrapnel factor.

There are guys out there that can make you a duplicate tank but what I see for custom tanks might be 1500-$2k.

 

[95burban]

I would weld it.

 

[Hipster]

Have done stuff like this, it depends on one's patience with a hammer and dolly and/or shot bag. To fashion a convex/concave piece depending on how you go about it, like this, isn't terribly difficult. A 4x4 or 2 screwed together and shaped with a grinder to form a buck you can hammer and shrink metal over or a shot bag you can work in a concave shape into. Gas is thinner, has smaller molecules, than water, so welds need to be pressure checked or at least checked with gas and not water before body fillers etc. are applied. I use a mig and double check stuff for weld porosity as I don't have a tig nor am skilled in using one but it would be a better choice. Never really had any success with epoxy over a bad place products and gas especially when concerning ethanol content. Often times need to do some additional welding after leak testing.

 

[RichLo]

Had a chance to run a some scotchbrite flap wheels on it to get a better idea what I'm dealing with.

Lots of pinholes but still very thick metal, These tanks weren't made of thin sheet metal that modern tanks are. The inside of the tank is near perfect with hardly any visible rust. I'm not concerned about the integrity of the rest of the tank witch is another reason I dont want a liner on the inside. I want to keep the inside pristine bare metal.

Seriously considering 2-part epoxy at this point. Thats a lot of pinholes for a welder to fix.

 

[Hipster]

Looks like an old puncture wound was there under all that. Was that epoxy under there as well? I think doing it with epoxy will result in the same thing again but maybe last enough to get through the season. Idk, the setup on that tractor but I'm funny about gas dribbling down over hot engines and exhaust etc.

 

[1990Z71Swede]

If it where me I would TIN/LEAD that. Period correct repair and will last forever.

There are special flux/Solder/Tinning pastes that contains Tin, Lead and some other good stuff. That alone would probably be enough to seal it.

But you should really sand blast the pitted area first. It will be much easier to get the flux down into the pores real good that way. One of those hand held spot blasters will do.

Found this, read the tinning part, the paste is mentioned there

Lead wiping/filling restoration and repairs - tech torque

Lead wiping isn't hard, you just need the right equipment and plenty of practice

www.whichcar.com.au