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Technical Any body know best way to make gas tank safe to cut and weld on.

Discussion in 'The Hokey Ass Message Board' started by rtp, Nov 18, 2017.

  1. rtp
    Joined: Aug 14, 2007
    Posts: 221

    rtp
    Member

    Tank on my 48 olds started leaking some time on the last week ,of course after filling it up. Leak is on bottom mid tank ,but not near sump in center.
    Plan is to pull it out ,make safe ,fix it ,seal it . Any suggestions.

    Sent from my VS987 using The H.A.M.B. mobile app
     
  2. Deuce Daddy Don
    Joined: Apr 27, 2008
    Posts: 5,544

    Deuce Daddy Don
    ALLIANCE MEMBER

    Purge with co2 while welding.
     
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  3. k9racer
    Joined: Jan 20, 2003
    Posts: 3,091

    k9racer
    Member

    Remove and carry to a radiator shop. Or as Deuce Daddy Don said purge with co2. After draining and washing the gas tank . I just place the filler neck on the tail pipe of my truck and let it run for 15 min or so, while still running I weld on tanks with no problem.
     
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  5. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,413

    southcross2631
    Member

    New tanks are cheap, but if you must repair yours . Pressure wash the inside with soap and water. Stick a hose from the exhaust of a running car in the tank and weld away.
     
    verde742 likes this.
  6. Yep- clean it well, wash it inside and out. Purge the air out from inside the fuel tank with CO2 from a welding cylinder or exhaust from a running engine. That's the way to do it.

    One way may be easier than the other for you to set up but they both work. The idea is to displace the oxygen and eliminate that one leg from the fire/explosion triangle - fuel-heat-oxygen.

    image.png
     
    sunbeam likes this.
  7. Depending on the size of the hole{s} , I have used J.B. Weld or some such . Even did this on a fuel tank on my semi. Still holding when the truck went to its final resting place many years and miles later.
    Using the exhaust is effective as well.

    Ben
     
  8. Seen it done filled with water

    And the exhaust pipe from a running car also


    There are good fuel tank repair epoxies out there ( like jb weld ) $ but made for fuel and can be applied right over a leaking area used them in the past with great success
     
  9. khead47
    Joined: Mar 29, 2010
    Posts: 1,789

    khead47
    Member

    Just rub the leak with a bar of Ivory soap. Don't laugh- it works. Carry the bar with you in case of rain.
     
  10. Works like magic till it gets wet.
     
  11. Blue One
    Joined: Feb 6, 2010
    Posts: 11,460

    Blue One
    ALLIANCE MEMBER
    from Alberta

    Speaking of JB weld do any of you guys know if you can mix any type of solvent into it to make it into more of a paste without making it to where it doesn’t work as usual ?
    I have a use in mind for it but it’s a little too thick (putty) in the usual state when mixed.
     
  12. rusty rocket
    Joined: Oct 30, 2011
    Posts: 5,053

    rusty rocket
    Member

    Back in the 80s I soldered my 47 ford tank. Never had a problem with leaks after that.
     
  13. 57Custom300
    Joined: Aug 21, 2009
    Posts: 1,424

    57Custom300
    Member
    from Arizona

    Back in the 60's I filled mine with water and used a old time soldering iron to solder it. The iron had a tip on it that was 1/2in diameter. May have been used for body work using lead.
     
  14. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,802

    jimmy six
    ALLIANCE MEMBER

    Exhaust pipe from a running car was an old tried and true way on an empty tank off the car. The guy stuck a garden hose down in the filler for about 10 minutes the made the repair with a torch set up. I've watched it done and then had to do it on a motorcycle tank.
     
  15. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    Got 'most' of the varnish-fuel fumes out, put the tank outside, around the corner of the garage w/the fill pipe up, stuck a torch in, heard a roar as the tank shot across the lawn!
     
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  16. seabeecmc
    Joined: Jan 28, 2005
    Posts: 1,185

    seabeecmc
    ALLIANCE MEMBER

    When you're absolutely sure that it's free of fumes, for good peace of mind place a coil of model cannon fuse in tank and place unit in a safe spot. Light and seek cover. If clear proceed with repair. Ron cannon fuse.jpg
     
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  17. OLDTINPUSHER
    Joined: Apr 28, 2009
    Posts: 572

    OLDTINPUSHER
    Member

    Growing up an old timer down the road would repair leaky gas tanks on the car !! He would put car on lift running, put hose from exhaust into gas tank. After 15 minutes he would solder leak shut. You could hear the gas in the tank boiling !! He lived into his 90's.
     
  18. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    Which kind of JB Weld are you using? I get the "regular" stuff (in tubes) from the hardware store, and if anything, it's too runny for most uses. I end up building little "dams" of .masking tape to keep it where I need it. I did buy some "High-Heat" JB Weld that came in sticks (not tubes), and it was an absolute bitch to mix.
     
  19. Blue One
    Joined: Feb 6, 2010
    Posts: 11,460

    Blue One
    ALLIANCE MEMBER
    from Alberta

    Yes it’s the high heat putty that I want to get a better mix with and maybe make it easier to work with.
    I’m going to mix up a tiny bit and add some acetone and see if it still cures properly.
     
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  20. putz
    Joined: Jan 22, 2007
    Posts: 636

    putz
    Member
    from wisc.

    wash tank out with dawn dish soap , drain , l have used east wood liquid tank sealer follow instructions , last time i did this i used a funnel with a 5/16 " opening next day i checked tank and put everything away the funnel was laying on floor picked up 5/16 " hole sealed shut ........ used db weld stick on another tank ,works better with wet finger went applying ..
     
  21. Someone is going to try that.

    Worked at a place with a guy who wanted to make a BBQ out of a 55 gallon drum. It was holding lacquer thinner. He put a torch to it and blew a hole in the roof.
     
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  22. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,306

    henryj1951
    Member
    from USA

    ^and seek cover. <----- no $#!T
     
    Last edited: Nov 19, 2017
  23. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,306

    henryj1951
    Member
    from USA

  24. kelzweld
    Joined: Jul 25, 2007
    Posts: 295

    kelzweld

    If you purge the oxygen from the tank with an inert gas you'll be safe for welding. Pure argon is inert.
     
    Last edited: Nov 19, 2017
  25. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    CO2 is stable. Other compound forms like CO are able to further combust IIRC. And Oxygen and other constituents of contaminated or mixed air.
     
    Last edited: Nov 19, 2017
  26. G-son
    Joined: Dec 19, 2012
    Posts: 1,277

    G-son
    Member
    from Sweden

    CO2 is the PRODUCT of carbon burning, the oxygen is "spent" and can not cause any more combustion. That is why we use it in fire extinguishers to put fires out.

    Personally, I'd prefer to mostly fill the tank with water, and then use an inert gas for the small space above the water. With water uou are SURE there is no oxygen, where there's gas, it is hard to be completely sure all the oxygen is gone. As long as the volume of gases in the tank is small, an explosion would be relatively small too - so even if it goes bang, it'll be a smaller bang and most likely not a tank flying around.
     
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  27. winduptoy
    Joined: Feb 19, 2013
    Posts: 3,334

    winduptoy
    ALLIANCE MEMBER

    It has worked really good for me and no open flame, spark producing work required.
    http://www.caswellplating.com/epoxy-gas-tank-sealer.html
    I put a bunch of sheet metal screws in the tank, shake them all around, to loosen up the rust. Dump them back out when you are done, rinse again.
     
  28. Fabber McGee
    Joined: Nov 22, 2013
    Posts: 1,286

    Fabber McGee
    Member

    You have apparently never used a CO2 fire extinguisher. It is heavy and displaces the oxygen at the base of the fire, smothering it instantly.
    When I was in the business of repairing and building aluminum boats I welded cracks and made modifications to dozens of gas tanks. Replace the air in the tank with CO2 and they are completely safe to weld. CO2 is the cheapest of the inert gasses, so it is the obvious choice. I would charge with CO2 from a welding gas bottle through the fuel outlet to engine fitting when I could, or just drop a hose in the filler and tape around it so it didn't leak. Set a good flow on the regulator, maybe 15 or 20 CFM. Then make sure the vent is at the highest point so the tank is full of CO2 with no air pockets (remember it's heavy and fills from the bottom). You can smell the CO2, it stings your nose. When the tank is full of CO2 the gaseous vapor coming out the vent will smell like gasoline but will sting your nose (try it). One time I welded a cracked weld on the top of an air boat tank that had 6 inches of gasoline still in it. The tank was in an awful spot and would have required pulling the engine to get it out of the boat. The vent hose ended way up at the top of the prop cage and when I could smell the CO2 coming out the vent I got curious about flammability. I took a little propane torch up there and held it in front of the end of the vent hose. It wouldn't burn within about 10 inches of the vent where it finally got enough oxygen from the air in the shop mixed in. Welded the crack and they had the boat back that same morning.
    Another time I had to weld a heavier bottom (3/16) over the outside of a thinner one (1/8) on a cabin cruiser with a full interior and full of spray foam (insulation) flotation. No way to remove it in the weld zones, so I just threw a CO2 hose in the boat and let it fill the hull with non combustible gas. I would check to see how high the level of the gas was by going in with a little propane torch then fire it up and lower it until it got to the level of the CO2 where the flame would go out. When the level was above the weld area it was time to weld.
     
    pitman likes this.
  29. I have seen guys just run exhaust gas through them too.
     

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