acem 1,957 Posted May 17, 2020 Share Posted May 17, 2020 I need to stop the leak on my portable diesel fuel tank. It's a rectangular box tank I use in the back of my pickup and leaks in a square bend on the bottom of the tank. I have welded gas tanks before. Empty fuel, air out, duct exhaust into the tank while welding. However I am concerned diesel won't evaporate and may ignite. I don't want that! How do Y'all weld/repair leaks in a diesel tank? Thx-Ace , Quote Link to post Share on other sites
Doc Egor 75 Posted May 17, 2020 Share Posted May 17, 2020 IH procedure to weld leaks in diesel tanks in the manuals was to fill the tank with fuel , peen the area to stop the leak and then overlay a patch and weld it. Probably best done outside. 1 1 Quote Link to post Share on other sites
bitty 6,677 Posted May 17, 2020 Share Posted May 17, 2020 You can get a co2 tank from a welding supply place to purge the inside of the tank out. I have welded diesel tanks before Quote Link to post Share on other sites
dale560 2,411 Posted May 17, 2020 Share Posted May 17, 2020 Diesel won’t usually explode like gas. We have washed diesel tanks out then welded them. Quote Link to post Share on other sites
lightninboy 681 Posted May 17, 2020 Share Posted May 17, 2020 I knew a guy on the internet who welded a tractor gas tank. Pulled the tank off this morning, pressurized it and found the leak. Put patch on it and tig'ed re pressurized it and re-installed, looks good Quote Link to post Share on other sites
mjcolemn 16 Posted May 17, 2020 Share Posted May 17, 2020 I'm not saying it's the right way.... but if it's a small hole fill the tank, rub a bar of soap in to the hole / crack to stop the leak temporarily then weld a patch over it. 1 Quote Link to post Share on other sites
hanniedog 127 Posted May 17, 2020 Share Posted May 17, 2020 Bitty you have probably welded everything except a butt crack. 1 Quote Link to post Share on other sites
Finney 1,317 Posted May 17, 2020 Share Posted May 17, 2020 I use argon to purge because I have it on hand. 1 Quote Link to post Share on other sites
AKwelder 2,127 Posted May 17, 2020 Share Posted May 17, 2020 1 hour ago, Finney said: I use argon to purge because I have it on hand. I like argon better, it is heavier than air and stays in the tank. Like has been suggested, empty it, purge it, and weld. Don’t get in to much of a hurry you said it’s cracked at a bend in the metal? You might want to really check it over. Some of those can run a long ways, and be a bugger to chase. 1 Quote Link to post Share on other sites
Tmtbob 746 Posted May 17, 2020 Share Posted May 17, 2020 Buddy of mine would steam it for a bit then fill with water and weld. Quote Link to post Share on other sites
Paystar5000 213 Posted May 17, 2020 Share Posted May 17, 2020 37 minutes ago, AKwelder said: I like argon better, it is heavier than air and stays in the tank. Like has been suggested, empty it, purge it, and weld. Don’t get in to much of a hurry you said it’s cracked at a bend in the metal? You might want to really check it over. Some of those can run a long ways, and be a bugger to chase. What he said about the crack being bigger than you think. Those tanks are only like 14 ga? I would weld the crack as best you can and then put some kind of reinforcement over it. I had one of these tanks a few years ago that I would weld and then it would start leaking somewhere else. Due to NY loving to pour salt on our roads I have welded patches on a bunch our our truck fuel tanks due to rusting out. I have never purged one and never had a problem. Not saying purging is not a good idea just never done it. Quote Link to post Share on other sites
vtfireman85 6,156 Posted May 17, 2020 Share Posted May 17, 2020 2 hours ago, Finney said: I use argon to purge because I have it on hand. I have seen charts on purging, but it takes longer than you think, is there a formula? Quote Link to post Share on other sites
vtfireman85 6,156 Posted May 17, 2020 Share Posted May 17, 2020 4 hours ago, acem said: I need to stop the leak on my portable diesel fuel tank. It's a rectangular box tank I use in the back of my pickup and leaks in a square bend on the bottom of the tank. I have welded gas tanks before. Empty fuel, air out, duct exhaust into the tank while welding. However I am concerned diesel won't evaporate and may ignite. I don't want that! How do Y'all weld/repair leaks in a diesel tank? Thx-Ace , great topic, I have the same issue I was just debating on the other day. Quote Link to post Share on other sites
Delta Dirt 2,042 Posted May 17, 2020 Share Posted May 17, 2020 J-B WELD-------and probably some other similar products on the market now. If skeptical about condition of remainder of bottom-------lay a blanket of fiberglass over it. Those thin skin (and stressed or rusted) tank walls do not like heat very much. ******* Glad to see our buddy Ace back on the farm and enjoying "what all comes with it"!!!!!!!? DD 1 Quote Link to post Share on other sites
New Englander 1,840 Posted May 17, 2020 Share Posted May 17, 2020 1 hour ago, AKwelder said: Some of those can run a long ways, and be a bugger to chase. Stop drill ahead of the crack? Quote Link to post Share on other sites
shot_gun_red 156 Posted May 17, 2020 Share Posted May 17, 2020 5 hours ago, acem said: I need to stop the leak on my portable diesel fuel tank. It's a rectangular box tank I use in the back of my pickup and leaks in a square bend on the bottom of the tank. I have welded gas tanks before. Empty fuel, air out, duct exhaust into the tank while welding. However I am concerned diesel won't evaporate and may ignite. I don't want that! How do Y'all weld/repair leaks in a diesel tank? Thx-Ace , i welded mine , its a 100 gal square tank had a piss poor 4" factory weld at top of side . I cleaned up side with grinder and wire welded it after it was empty . if your a decent welder and don"t blow threw you wont die ! I didn"t ever air it out . I"ve done alot of old tank fixing. Got my experience in the 80"s 1/4 up a old 10000 gallon gas for hog huts . Quote Link to post Share on other sites
AKwelder 2,127 Posted May 17, 2020 Share Posted May 17, 2020 45 minutes ago, New Englander said: Stop drill ahead of the crack? I don’t think so, find the ends and weld the whole length. Cracks eventually go full thickness of the base metal (so they leak) and may propagate further at a less than full thickness. Metal that has a crack that you just weld the surface of and leave a defect underneath normally cracks again. Quote Link to post Share on other sites
mike newman 3,201 Posted May 17, 2020 Share Posted May 17, 2020 ….If you need to repair a "commercial" Diesel tank...i.e. non automotive ….just make sure there is diesel well above the crack ….and weld away...….apart from a bit of smoke etc arou nd the leaking fuel.....this is the best way to repair ..if you insisting on ''purging '.....be bloody carefull….especially if the ambient temperature is high......they are very dangerous with fume residues...not as bad as petrol, obviously...but will still take out the unwary welder...... Mike 1 Quote Link to post Share on other sites
gee-haw 2 Posted May 17, 2020 Share Posted May 17, 2020 Don’t over complicate it. I had the same problem and got some sort of two part epoxy at NAPA. Put the epoxy on it and it hasn’t leaked in years now. Quote Link to post Share on other sites
Finney 1,317 Posted May 18, 2020 Share Posted May 18, 2020 8 hours ago, vtfireman85 said: I have seen charts on purging, but it takes longer than you think, is there a formula? Figure the cubic ft. in your tank. Flow meter has cubic ft. per hour floating ball. If your tank is 30 cubic feet I set the flow meter for 60 cu.ft. per hour and wait 45 minutes. 2 1 Quote Link to post Share on other sites
Gearclash 1,218 Posted May 18, 2020 Share Posted May 18, 2020 1 hour ago, Finney said: Figure the cubic ft. in your tank. Flow meter has cubic ft. per hour floating ball. If your tank is 30 cubic feet I set the flow meter for 60 cu.ft. per hour and wait 45 minutes. I’ve done this too. It works. One comment, argon works well to purge a tank as it is heavier than air, so long as the only opening on the tank can be positioned on top. 1 Quote Link to post Share on other sites
dale560 2,411 Posted May 18, 2020 Share Posted May 18, 2020 1 hour ago, Finney said: Figure the cubic ft. in your tank. Flow meter has cubic ft. per hour floating ball. If your tank is 30 cubic feet I set the flow meter for 60 cu.ft. per hour and wait 45 minutes. 5 minutes ago, Gearclash said: I’ve done this too. It works. One comment, argon works well to purge a tank as it is heavier than air, so long as the only opening on the tank can be positioned on top. Learn something new everyday. 1 Quote Link to post Share on other sites
vtfireman85 6,156 Posted May 18, 2020 Share Posted May 18, 2020 4 minutes ago, dale560 said: Learn something new everyday. We purge kegs and carboys for brewing to prevent oxidation, but use co2, I figured Finley would have some good info on the subject, also for welding stainless, I try to fill the vessel with water as much as I can to reduce the amount needing purging. Quote Link to post Share on other sites
ThirdGenRed 162 Posted May 18, 2020 Share Posted May 18, 2020 I also have one of those steel rectangular 100 gallon diesel tanks which developed a leak near the top on the side where the baffle inside was spot welded. It cracked at the spot weld and would leak so I drained the tank and hot pressure washed it out and welded it up. I also welded a plate over that spot because the metal seemed to flex quite a bit there, don't know why. I did not blow up and it has held for almost ten years now. I fixed it outside and was told after I welded it that I could have parked a running gas pickup next to where I was working and piped the exhaust into the tank to prevent an possible explosion. It sounds like that would work, but ended up not needing it. Quote Link to post Share on other sites
Rawleigh99 1,111 Posted May 18, 2020 Share Posted May 18, 2020 For non structural fuel tank repairs I have had excellent results JB welding a patch over the leaking area. You can use a Shop-Vac on a diesel fuel tank to keep the diesel from leaking out while you glue on the patch. For rust holes I use quarters for patches. Knockouts from electrical boxes also work if they don't have the slot in them. In your case you could bend a piece of sheet metal at 90° and epoxy it on if you don't want to risk welding it. 1 Quote Link to post Share on other sites
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