Steel Tank Needs Fixing

I've got a slow leak at the front mounting post on my Interstate tank. It's very slow. The only way I caught it is that the tank was off and sitting on a masonite table for a month. Does anyone know what the posts looks look like under the brazing? Did they braze them originally or has someone been at it? Lastly, how do you braze a gastank without blowing it up?

Thanks,

I have seen them brazed before that appeared to be factory.
They are easy to re-braze, flush them with soapy water and then fill the tank with inert gas. Co2 or argon works. Let it flow through long enough with the air escaping at the top to be sure the oxygen is gone and then weld it with the purging gas still flowing. Do it where there is plenty of air circulation as the fumes that escape from the tank will burn after they mix with air. Jim

PS -Filling with water is a bad idea. Lost a good friend that way when he tried to weld a tractor tank full of water..

When you remount the tank get rid of the studs and use exhaust mounts. That will eliminate the cracking problem.

What do you mean by " exhaust mounts" Jim?

Done many tanks.
Easy, empty petrol, fill to the brim wth water & empty out.
Any petrol left will float to the top & filling it up will force all the fumes out. If you are unsure, do it 2 or 3 times.
Hope your tank hasn't got any of that sealer stuff in or you won't be able to braze it.

As Jim said the safest way to do it is to flow in Argon or CO2. Other methods are just too risky.

gtsun said:

What do you mean by " exhaust mounts" Jim?

Click to expand...

I mean the rubber biscuits with a stud on each end like mounts the stock muffler. Jim

Flo said:

Done many tanks.
Easy, empty petrol, fill to the brim wth water & empty out.
Any petrol left will float to the top & filling it up will force all the fumes out. If you are unsure, do it 2 or 3 times.
Hope your tank hasn't got any of that sealer stuff in or you won't be able to braze it.

Click to expand...

That is what my friend always said too. I was standing outside the shop when the windows came out. He was at a professional welding shop. Jim

This must not be stock. The mounts in the back are threaded in. Would it be best to grind it down to bare metal to see what's under there and start over?

That is definitely not stock. Originally there would have been a threaded hole with the stud screwed in. Now the stud is welded in. I might be tempted to cut it out and weld in a new female threaded insert. Jim

Fair amount dry ice dropped in maybe with a bit of water and heat some till its fogging out the open lid then have at it. Tip so dry ice ain't near weld area. Good blast by CO2 extinguisher might do in a pinch but rather expensive to recharge. Personally me and my buddy here would grind a roughened clean ring around the stud if it was structural sound, then JBWeld the snot out of it and forget about it. Its a removable patch if welding needed later.

Might be educational to fill a tub and dunk tank under to see where bubbles show up. I saved a trashed over head 300 gal tank running sheet metal screws in the rust pin holes, so far 12 yr now gas tight. But then again I put grass straws in my month and pee outside a lot, just not in same spot till it rains.

If you want a temporary fix that lets you ride you can grind the whole flat area and make a plate that covers as large an area as possible, beyond the damage of course. Drill a clearance hole for the stud and bond this to the tank with a good metal based epoxy. Don't squeeze out too much of the adhesive, leave a 1mm or so thickness. I did this on my Roadster tank and has lasted 10 years. May not be good enough for a fully fuelled Interstate job though. Also depends how far the crack has spread, mine were cracked half around the insert on a 1" dia. If its done neatly and cleaned up with filler it will look almost original.