Fuel tank leak

[mikey]

My fuel tank is leaking. I am going to replace it Friday. I bought a tank from Kublo's Surpluss for $80 without the pump.

The process seems simple, a whole 4 pages from TM 9-2320-209-20-3-1 (4-29 - 4-32).

Are there any suggestions, tips or tricks you guys with experience can provide me while the tank is being swapped? Anything I should look for with the pump or any other suggestions would be appreciated.

Thanks

Mikey

 

[Z71]

I never removed the tank on mine, but I took out the pump and replaced the gauge sending unit. I would recommend replacing the electric transfer pump gasket when you install it on new tank . I would also carefully inspect the tank straps for corrosion or damage and replace the strap bolts with fresh rust free bolts and nuts of at least grade 5 or higher.

 

[cranetruck]

The tanks are made of steel and will start to rust in areas out of sight, mainly between the support brackets and the tank itself. Remove the paint and check for rust. You certainly don't want rust on the inside, micron sized hard particles will ruin you FDC and IP...

 

[mikey]

The tanks are made of steel and will start to rust in areas out of sight, mainly between the support brackets and the tank itself. Remove the paint and check for rust. You certainly don't want rust on the inside, micron sized hard particles will ruin you FDC and IP...

You nailed it. Within a week of getting my deuces home I changed the fuel filters to spin ons. When I removed the filter housings, they were fulled with rust at the bottom.

Additionally, the leak is coming from under the support bracket, so you nailed that too. I'll be able to assess how bad the tank is once I get it off. If it's salvageable, I'll fix it and keep it in my pickup to transfer wmo.

Ironically, I won the trucks in November, moved them from GL in Jan, from ss member Paulfarber's house in Feb then from Kublo's surpluss Memorial Day weekend and finally got them home. The entire time since we recovered them in Jan, there wasn't a drop of fuel leaking. Last weekend I added 16oz if Diesel Klean to a full tank of diesel and the leak started within days. Not blaming the diesel klean because I'm sure the tank was on it's last legs, but I'm willing to bet it accelerated the process.

I'll post pictures when I get the tank off.

Mikey

 

[Tinwoodsman]

I had several small leaks (holes) in my tank. I took it off and did an acid wash to flush out any defects. Had the tank leaks brazed and the coat is with KBS tank seal. It turned out great.

 

[mikey]

I had several small leaks (holes) in my tank. I took it off and did an acid wash to flush out any defects. Had the tank leaks brazed and the coat is with KBS tank seal. It turned out great.

Your thread was the first one I read when I searched "fuel tank leak".

Mikey

 

[Wildchild467]

when you swap out the pump, make sure the pump is at the correct depth in the tank. when i checked mine, it was about 2" too high... so that a couple gallons of fuel i would be out of if i ever ran my deuce that low (which i dont). also wouldnt be a bad idea to swap out the hose that goes from the bottom of the pump and to the top of the tank if it looks skanky.

 

[mikey]

I replaced the tank without issue. Thanks everyone for the tips. The in tank pump looked fine. The strainer was in good condition, the hose looked brand new and the pump was on the lowest depth setting.

The idea to buy new strap bolts was a great one. The original bolts were so covered in carc and rusted underneath the carc that it was easier to cut them and use the new bolts.

In addition to the advice here, the only suggestion I would make to someone who hasn't changed a fuel tank is a bag of (qty 10) 10-32 x 1/2 screws for the in tank pump. Mine were so covered in carc and so old that they stripped easily and I had to use pliers to get half of them out.

Thanks all.

Mikey

 

[Welder Sam]

Good info. Thanks to all

 

[Tinwoodsman]

Glad it went well Mikey.

 

[cranetruck]

........
In addition to the advice here, the only suggestion I would make to someone who hasn't changed a fuel tank is a bag of (qty 10) 10-32 x 1/2 screws for the in tank pump. Mine were so covered in carc and so old that they stripped easily and I had to use pliers to get half of them out.

Thanks all.

Mikey

Glad you got it done...
Regarding the 10-32 screws, get a few star washers also to make sure there is a good ground connection. The fuel level sending unit is grounded via those screws.

 

[LongueCarabine]

The 109 my brother and I got a few weeks ago has a painfully slight fuel leak right under the rear tank crossmember. The bad thing is, it's about half full of fuel. Doggone drain plug won't come undone, so I'm just letting the fuel drip into a pan for now.

I put some penetrating oil on the plug and will try to get it undone tomorrow. The problem is the square hole is starting to round off. I may have to go get a cheap siphon to empty the tank if the plug won't come off.

It's just a very slight pinhole, so I am probably going to just try JB Weld for now, unless I find a lot of crud in the tank. In that case, I may take it to a shop for cleaning and a proper repair.

LC

 

[mikey]

The 109 my brother and I got a few weeks ago has a painfully slight fuel leak right under the rear tank crossmember. The bad thing is, it's about half full of fuel. Doggone drain plug won't come undone, so I'm just letting the fuel drip into a pan for now.

I put some penetrating oil on the plug and will try to get it undone tomorrow. The problem is the square hole is starting to round off. I may have to go get a cheap siphon to empty the tank if the plug won't come off.

It's just a very slight pinhole, so I am probably going to just try JB Weld for now, unless I find a lot of crud in the tank. In that case, I may take it to a shop for cleaning and a proper repair.

LC

I wound up getting a new tank, but I used jbweld on the old one and I now use the old tank to transport WMO in my f150. It's nice because it's low profile and fits under the tonneau cover, which a 55g drum will not. The jbweld completely stopped the leak.

Anyway, I had the two pinholes under the crossmember area. I pinpointed the holes by sanding the crossmember areas down to the steel then filling the tank with water, 15 gallons or so, and letting sit on saw horses with the sanded areas exposed. After a few days you could see tiny rust spots around the pinholes over the newly sanded steel. The pinholes were in the center of the rust spots.

Good luck with it.

Mikey

 

[plym49]

When a tank rusts through to a pin hole, usually the metal in the immediate area is quite a bit thinner. I have had tanks with one or two pin holes and the process of sanding, as you described, all of a sudden presented a dozen or so more. Whether you solder, braze or JB Weld (I prefer Marine Tex over JB), 'wash' a good area around where the pinholes were to restore thickness to the affected area.

 

[LongueCarabine]

My tank has a fair amount of crud in it, would sure be nice to be able to drain the tank through the plug. Has anyone ever heated up the drain plug from the outside to see if that would help?

I've been putting PB Blaster on it (from the inside and outside) for a few days now and it still won't budge. The plug is rounding off and I really want to get it off before this becomes a bigger problem.

LC

 

[Heavysteven]

Just a thought you might weld a bolt in to the plug. I would be nervous about heating the plug from the inside.

 

[LongueCarabine]

Just a thought you might weld a bolt in to the plug. I would be nervous about heating the plug from the inside.

Thought about welding a bolt to it, but I think I'm gonna try to heat it first from the outside. Not sure if I wanna stick a torch inside the tank, sounds kinda risky.

I filled it up with water and let it run through for a while, then drained it. Now I am gonna get the shop vac and get the scale and the rest of the water out.

I wonder if hooking up the shop vac to get the fumes out will help? I doubt it has any diesel left in it, I let the water run for a while. Probably not much in the way of fumes left either.

LC

 

[plym49]

You might be able to heat it enough from the outside with a heat gun.

Filling a fuel tank with water to make it torch- or welding-safe is not foolproof. I recall that the Army recommended running the exhaust from a diesel engine through the tank. There will not be any oxygen and therefore you can safely use an open flame or arc device.

 

[Welder Sam]

You might be able to heat it enough from the outside with a heat gun.

Filling a fuel tank with water to make it torch- or welding-safe is not foolproof. I recall that the Army recommended running the exhaust from a diesel engine through the tank. There will not be any oxygen and therefore you can safely use an open flame or arc device.

Good advice. If/when you apply heat, apply it to the threaded bung instead of the plug. That will allow the "tank-threads" to expand and release the plug

 

[LongueCarabine]

Good advice. If/when you apply heat, apply it to the threaded bung instead of the plug. That will allow the "tank-threads" to expand and release the plug

Did just that, this afternoon. Didn't take much heat to loosen up the plug, but without it, that dang plug just wouldn't budge, even with a cheater pipe.

Now we commence to cleaning, acid washing and sealing.

Thanks for the replies.

LC