Welding on SC Gas Tank

Ken Christopherson

Well-known Member
Hello everyone,

Well, it finally happened. The ancient repair that was done on the '41 SC gas tank finally started leaking. Being that I have already put a lot of work into this tank, and it is original, I would like to keep it. My thought process is that I will cut out a 2" by 2" square section, and weld in a new piece of metal. I have washed the inside with dawn dish soap (twice), and rinsed with a LOT of water (basically just ran the hose into it and let it run for about a half hour).

I have welded on a motorcycle tank, and when I did that I ran a hose from a running car's exhaust pipe into the tank to try to avoid the horrific explosion. Anyone done the welding on a tank without issue after cleaning it? I'm looking for some pointers here.. I should have done this prior to restoring the tractor, but at the time the old repair was holding up well.
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I have welded more then one gas tank and done it one of 3 ways.

#1 hook up a cars exhaust and let it run and after about 30 minute do the weld while it is still hooked up.

#2 I filled the tank with water and then did the weld. It did seem a bit harder to do that way due to the steam problems and steam in a weld can cause odd problems.

#3 I welded a tank on a Jeep I had. I had to do some other welding close to the gas tank so I filled the tank as full as I could with gas drove it home then put in as much as I could when I got home. I started to do the weld tha twas close to the tank but well Murphy got me and I pout a hole in the gas tank while trying to do the other weld. So I put the flame out cleaned the area of the tank and then weld the hole back up. I then covered the tank with a big wet rag so I would not be as likely to make another hole in the tank.

Having a full tank did not let the vapors explode.

I have also done it by put a tank in a brush pile and light the pile and let the tank burn off but doing that can cause the tank to warp or bow out if the gas vapors explode.
 
It always makes me mad when someone says to run car exhaust into a gas tank so it doesn't blow up. Cars pump air into the exhaust so that the catalytic converter can burn the unburned gas. There is more than enough oxygen in exhaust to blow you up. The theory of welding below the gas or water line is sound, but you will fight pin holes forever. The liquidmcoming out while welding causes holes. The safest way is to get a tank of co2 and run that in there or use dry ice which does the same thing. If you know someone with mix gas for a mig that works too but is costly.

There are many non welding solutions that will work great too. Napa sells a tank repair puddy that works greatnand has been on my dc for 25 years or more. It works best when you put it on wirh gas leaking out.
 
Don't know back when I was taught to use the exhaust it was before the convertors so you may be right on that but I have enough engines around I'd probably use a tractor any how so it would still at least in theory work just fine
 
I spent several years working in a welding and machine shop. We sent the tanks to be welded to a company that used live steam to clean oil barrels. Had them flush the tank with live steam for a time to clean the tank. I was told that this process sweated the gas fumes out of the pores in the metal. We never had any problems but welded on them right away rather than let them lay around for a couple of days.
 
A lot depends on the gas tank. If the tank has a large hole in it to fill it or a sending unit which you can remove you can ignite mild gas fumes and it will just make a little poof noise. I usually wash one out and wave a flaming rag on a long stick over the filler hole to see if there is too much gas fumes before I start welding. Still if your's is rusted through that bad you much have a bigger area needing a fix. I once started welding a tank off a riding mower and ended up having to cut the entire bottom out of the tank and replacing it.
 
I have used JB weld to fix gas tanks. I clean it very thoroughly inside and out. Then rough up the outside with a sanding disk. If a large hole make a sheet metal patch. Make sure it is clean and rough. After the JB sets up then I seal the inside with tank sealer. Steve
 
I'm sure there's lots of ways of doing it, this is what works for me, raise with water two or three times, blow all the water you can out of it, set it out in the sun for a day with the cap and sediment bowl off, stick an air hose in it for 30 minutes, good to go, when I get done welding I Red kote it.
 
Go to Menards, then go to the plumbing department and buy a tube of SEAL-ALL , for $3.00 or so. It is gas and oil resistant. and i guarentee it to work. Like anything else read the directions.
 
When I have welded on gas tanks I start out by cleaning the tank out with a good degreaser like purple ZEP from menards. May do this 2 or 3 times. Before I start welding I pull a vacuum on the tank. I purchased a vacuum puller from that is made to work on A/C systems and adapted it to use for this. It works off a air compressor. After all is said an done I would use a good tank liner kit on it. I have had good luck with POR15
 
I'll always remember when I got my new Victor torches 40 some years ago. Local welder, machine shop, blacksmith had the cylinder depot and got me fixed up with the tanks and fittings. He told me " people will come with tanks and drums to cut open and fix, they'll send flowers to your funeral, but they'll still come with tanks and drums to cut open and fix"......Ron
"
 
i just leave the air hose blowing inside the tank. its just the vapours you want out anyhow. not telling you to do that either. i take my own chance.
 
Years ago while building a grain elevator in Iowa a gasoline bulk tank sprang a small leak. Tank was of 50,000 gallon capacity. Specialized welding company set up about 100 feet from where were working. Tank was welded with NO special prep while myself and total crew took a LONG coffee break!!! Tank was almost full and was told no problem if gasoline well above weld . OH and be sure to not burn through.
 
I would use that new JBweld stick. it is a putty that is made for gasoline and diesel fuel. I have used it on several things and it works very well.
 

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