welding a fuel tank leak

bluenosegoat

New Member
Dec 29, 2009
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arizona
So I've had a few people buying stock fuel tanks from me because theirs are leaking around the mounting studs. I would like to find a good way to fix them instead of trashing them. I've had very limited success with JB weld. I've learned that washing the tank with warm soapy water and then putting some dry ice in the tank as the co2 created will remove any fumes/oxygen which should make it safe to weld on? Just wondering if anyone out there has some experience welding fuel tanks. I am about to pick up some dry ice but I'm still pretty concerned about a fire or an explosion. Maybe its just worth replacing? Any safety precautions would be much appreciated.
I will be using a MIG welder if I get up the courage/stupidity. Thanks
 

Al.Fisherman

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Sep 9, 2009
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Calera, Alabama
I have brazed many tanks in the past 25 years. I take a hose from the exhaust of my car or lawnmower, to the filler inlet and let the tank warm up (empty as much out as you can). This will kill any fuel that is in the tank. Take my oxygen/propane torch and braze. This was shown to me by a barge welder. I'll run the torch by the fuel inlet, but have never had so much as a puff. CO2 or CO (not sure which) kills the vapor in gasoline, and will not ignite. After doing this it was shown to me that the liquid gas in the tank, when poured on the ground would not ignite.
 
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bluenosegoat

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Dec 29, 2009
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I have brazed many tanks in the past 25 years. I take a hose from the exhaust of my car or lawnmower, to the filler inlet and let the tank warm up (empty as much out as you can). This will kill any fuel that is in the tank. Take my oxygen/propane torch and braze. This was shown to me by a barge welder. I'll run the torch by the fuel inlet, but have never had so much as a puff. CO2 or CO (not sure which) kills the vapor in gasoline, and will not ignite. After doing this it was shown to me that the liquid gas in the tank, when poured on the ground would not ignite.
Thanks for the tip! Yeah that makes perfect sense with the co in exhaust removing the fuel vapors. I'm going to pick up a polypropelene/oxygen torch tomorrow and give it a whirl. I dont think I will have much success with the MIG on such light gauge metal and I've been wanting a torch for some other brazing projects. I tried some sheet metal with just Map gas but it just wont get hot enough with the brazing rod or with copper wire. Hope it works out- I have 4 tanks right now to fix.
 

rustycase

Gutter Rider
May 26, 2011
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Left coast
Yah, the mig is probably NOT the way to go for a repair.
Brazing would be far better.

Them tank sealer kits are expensive!

Good luck
rc
 

Mobbin'Deep

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Apr 16, 2010
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Far away from home
I took a leaky tank to a guy to fix it couple years ago, he did the same thing, ran a hose from car exhaust to the tank...he wanted $80 to fix afterward (wouldnt quote me before) though, so i let them keep it.

i just cut up a new tank to use on my custom one. The petcock bung was brazed on from factory so i assume the studs are aswell.
 

thegnu

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Sep 15, 2011
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freedom pa
I have always slipped an air line in mine an let it open at about 5 to 10 psi the volume of air moving through the tank is far greater than any fumes that could build up .
 

Al.Fisherman

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Sep 9, 2009
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Calera, Alabama
I took a leaky tank to a guy to fix it couple years ago, he did the same thing, ran a hose from car exhaust to the tank...he wanted $80 to fix afterward (wouldnt quote me before) though, so i let them keep it.

i just cut up a new tank to use on my custom one. The petcock bung was brazed on from factory so i assume the studs are aswell.
People in the past on one of these forums told me I was crazy.... Glad someone else has had the same experience. $80.00...now that's crazy. Wouldn't take me longer then 15 minutes to braze 4 studs after the tank was heated. Ummm $320.00/hr. I would do the same for $25.00.

This is my boat generator, 2 cycle.
 
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bluenosegoat

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Dec 29, 2009
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arizona
Thanks guys for the info- four tanks successfully brazed today. I used the exhaust from my van on the first two- about 7-10 mins each and on the other two I put the hose from my compressor set at about 15psi in the petcock hole. Both methods worked great. I sure wish I would have tried this long ago. I figure for the 60 bucks spent on the torch set, picked it up at the Home Depot this morning, it has already paid for itself fixing four motorbike tanks and I'm sure more to come.
 
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Cavi Mike

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Dec 17, 2011
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Rochester, NY
Dry ice to purge a tank of fumes? That's a bit over-the-top, don't you think? You also don't know if you've actually purged all of the fumes because both are gasses and they very well may mix.

Easiest and safest way without a sniffer? Fill it with water. Done and done.

Some odor of gas will remain but a few ppm(parts per million) is all you need to smell it but it's not going to ignite or cause an explosion.

And by the way, they can be TIG'd pretty easily.
 

BarelyAWake

New Member
Jul 21, 2009
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Maine
Honestly? I can't see the stock kit tanks being worth the expense, time & effort of a proper prep and liner in any way - not only are they of a poor quality and will likely need repairs (which will destroy the liner obv), a new replacement tank (stock) is cheaper than the liner materials, for twenty bucks or less I'd just get a new one if needed.

After seeing the long-term consequences of many a DIY tank liner, given the choice between an unlined tank and a DIY liner, I prefer uncoated tanks every time. All you need to do to keep them from rusting is use them, if you're going to store them for a long period - draining them and hittin' them with a coat of oil (like PB blaster) works quite well, even living right next to the ocean.

To each their own, but I've found DIY tank coatings to be far more problematic than they're worth. Some respond quite poorly to the ethanol content in today's fuel and tend to be sloppy regardless. All too often they're used incorrectly, poorly prepped, to try and seal small leaks or to try and "fix" a tank that's already been corroded through neglect - which ends up being only a temporary fix & much like "duct tape style" repairs, makes the problem far worse for you later, when the corrosion continues & the liner begins to peel & slough off.
 
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bluenosegoat

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Dec 29, 2009
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arizona
Turns out I have one out of four that still leaks a tiny bit- took 2 days to see it and its on my bike so owell, fix it latter. Still a bonus to have the right tool for the job-and I already sold the three tanks,I did let them sit with fuel for two days, so its paid for its self in less than a week plus some! Thanks again for the safety tips! I still have my graying hairs,granted the act of welding a fuel tank added some in worry I'm sure! Thanks guys!
 
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