Leaking fuel tank - looking for a welder

[Will Hansen]

Our '07 Contessa has just developed a leak (drip every 30 seconds) at the bottom of the mounting tab, straight down from the fill pipe on the drivers side. Of course I only discovered it after filling the tank. So far, my attempts to plug it with JB Weld 'Tank weld' epoxy have failed. And since it's a mounting point any such patch would be temporary. I can't find a repair shop here in the Seattle area willing to weld on a full tank. Does anyone know of a repair shop in Oregon experianced in this procedure? I don't see how the tank could be removed. From what I've read, welding a full tank is actually a reasonable thing to do as the ingredients of combustion are not all present.
Any suggestions?
Thanks!
-Will

[David T. Richelderfer]

Is it a crack, a tear, or a hole.  My Bluebird's diesel tank sprung a leak once and was leaking enough diesel to cover the rear window of the coach while I was traveling down the road.  That's how I was notified of the leak - the rear window was a mess.  Anyways, I took my little box of toothpicks and started jabbing them into the hole.  My guess is the wood fiber absorbs the diesel and expanded to plug the leak.  This was an "on the road" temporary fix and it held back almost all the leaking until we returned home.  The permanent fix was to get a semi-soft waxy stick, much like a crayon, made for plugging fuel tank leaks and press/rub the stick into/over the hole.  That was in the early 90s and I think it's still holding.  I have no idea what the trade name of that waxy stick was.  It was over 20 years ago.

Note:  One of the golfers in my Echo Men's League works for Cascade Natural Gas Co.  Earlier in his career he used to weld cracks and leaks in natural gas lines WHILE THE LINE IS UNDER PRESSURE with natural gas.  He said it's perfectly safe if the procedures are followed.  I would guess the same holds true for your tank leak problem.  Your first problem is finding that someone who knows how to do it.

[Joe Rhea]

Will
take a center punch and ping the weld if you can get to it. You don't have to hit it hard, all your doing is closing the hole up. After you get it stopped from seeping, clean  and rough up with a stiff wire brush. It has to be clean for the JB to stick ( no oil residue ). But you need to determine if it's a stress crack or pin hole

[Will Hansen]

Thanks guys.  I can't really see a crack or hole.  Just seeping fromalong the weld. Can't determine the exact point of origination. I'll try peening at a couple suspicious spots. I was able to chip yesterday's JB weld attempt out this morning.  I'd scrubbed it with steel brush and detergent but it seeps back so fast that I can't get a clean surface to last long enough for adhesion. Gotta stop the seep before I try that again. Clearly the weld has fatigued so I need a re-weld.  I'll start by calling Monaco on Monday.
-Will

[Lee Welbanks]

The only way I would weld on a tank is to empty it and purge it out with nitrogen or argon, that way you know your safe. Welding on a wet diesel surface is asking for trouble, fire for one and a crap weld for the other.

[John Hennessey]

We had a similar problem in our boat. We got a cheap pump on eBay and then pumped the contents into 55 gal drums. We had a diesel truck so we filled it up with that. I don't see any other option for you. Are you sure it isn't leaking somewhere else and running down to the weld?  Linda Hennessey

[Ed Dubois]

My experience with a tank problem also comes from boating. Although it's a fuss, draining your fuel into other containers is the way our mechanics always recommended too. If you don't have access to a 55 gallon drum jerry cans or pails work fine too. One extra benefit to emptying out a tank is that you can also clear out whatever contaminants have collected in the tank bottom over the years.

[David T. Richelderfer]

I agree with emptying the tank for safety's sake.  But the vapor (read: combustible fumes) space in a fuel tank, whether it's empty or partially filled with diesel, is what explodes and causes damage.  In my experience from being raised on a farm, you should empty the tank of all fuel and fill the tank completely with water to eliminate the vapor space.  This being said, again, I know a guy who used to weld cracked natural gas lines while the lines were carrying natural gas.  I would not like that job!  Once oxygen gets in the line, or tank in this case in the vapor space, then you have two of the three components for a fire and explosion.  Add enough heat from welding and kaboom!  Oxygen, fuel and heat...

[Steve Huber]

Will,
The tank can be removed. The shop I use for maintenance had one removed from a Monaco era Beaver (Contessa I think) a few years ago but I don't know how they got it out. Let me know if you want me to check with them as to how they did it. If you haven't already, check the service provider list in the Suppliers Comments and Kudos board. There are quite a few service providers in the WA and OR area listed. Sounds like a stress crack if it started after filling the tank, although the tank weight appears to be supported by the rails it rests on. Could have been caused by over-tightening the hold-down bolt at the factory. I guess.
Good Luck, Steve

[Michael Peters]

Will, I've repaired diesel fuel tanks numerous times on off highway equipment. It starts with a vaccum on the tank to slow the leak or seep in your case. I use a mig welder for the start stop control. Depending on the metal thickness, one pass will seal it. Sometimes short stitches with peening to seal pinholes. Diesel is not real flammable as long as you don't let it get out of hand. I clean really good before starting.Wirewheel or sanding disc on weld area.I use an airblow nozzle to snuff out any flames. Naturally keep adequate fire extinguishers handy. But no its not explosive like gasoline. My worst repair was 200 gal. fuel tank on blasthole drill and a flyrock had punctured down low on tank with 1/8"hole . Fuel was squirting. I welded while operator blew out the fire with blowpipe.  Hope this helps!     MIKE 

[Will Hansen]

Thanks Michael,
I wish there was someone with your experience here in Seattle.  Everyone I've contacted seems unfit to deal with it and/or has no experience with coaches, or lectures me on how a full tank could/should never be welded. I've made an appt with Monaco/REV group in Coburg as they say they fix these every so often.  Thankfully Good Sam will take some of the $ting out of it, apparently.

I'll close this thread with a recap after I get it fixed.
-Will