weld came off with screwdriver poke

[tracksfan]

For years my 580K has leaked fuel from a crack on the fuel tank/frame where the loader arm mounts to the left side. It looked to me like the bead of weld had cracked and needed to be redone. I don't feel comfortable welding on a fuel tank myself, I figured I would get a pro to do it but never got around to it and its more a nuisance than an urgent repair.

So now I've got the machine up for sale and a potential buyer had asked for some pics of the crack. As I was looking more closely at the crack I realized it looked like chipped paint. So I started poking at it with a screwdriver. As I worked my way around I bumped the "weld bead" and it fell off. What the heck?

Now I'm confused, it looks like the weld bead is a bead of sealant or caulk. Did it come from the factory like this? It doesn't look like it was ever welded underneath. This seems very strange to me, is there a reason why it shouldn't be welded?

I looked in my parts book, it only shows the metal pieces and no type of sealant.

I've heard the 580Ks are known for this crack, is it possible that its not a welded joint at all but sealed with sealant? In that case its more cosmetic than structural.

I will have to wait for the weather to warm up before I can monkey around trying to reseal it.

By the way, the hydraulic cylinder mount below it appears to be welded and not leaking. Around 4000 hours on the machine and no other cracks, its in pretty good shape overall.

Anybody know?

Thanks

 

[Auctioneerhere]

Pull the tank, have it cleaned properly, weld it shut correctly & be done with it.

Around here we have a place that cleans rail road tank cars & they clean out smaller tanks for people that ask.

 

[motrack]

On his backhoe the fuel tank in made into the machine frame...... it cant be pulled off and repaired. Are you sure thats not just weld flux that was never scaled off before painting?

 

[Yepblaze]

I think that's just a putty like substance.

As I recall we just filled the tank V'd em out and welded em up.

 

[tracksfan]

Sounds like the concensus is to weld it up. Thanks for the replies.

 

[Davo]

Mate I'm a Body Maker, I'm no exper but I can say that it's very common for a welded and ground joint to be sealed with a bead of sealant just to 'pretty it up' so they all look the same. I would clean the whole area, drain the tank, block the lines, fill with water and arc weld it. Water will flow from the leak but just tac it on and off and you will get it. Dont get your gloves wet! If your not confident just prep it and call in a welder.

 

[fast_st]

Hmm, if its just a seam leak, you might clean the area with a brake type solvent, run the tank down low or drain it, wirebrush the area, apply a partial vacuum to the tank (shop vac would be fine for diesel) clean the crack and brush on some seal-all its a good fuel compatable sealer, dries quick, not great if there is mechanical abuse in the area. A few of the epoxy type coatings, some of the jb weld etc tend to soften with fuel exposure

If its a super fine crack, and you can spare the machine for 2 days, drain and clean it like crazy, solvent and compressed air wire brush and all. Apply Loctite green, wicking threadlocker to the area. Other than not carrying the FAA certification, its used for sealing weld pinholes and small cracks in aviation fuel tanks. It likes 48 hours to cure up.

 

[hankobc1]

Check with your dealer he will be able to tell you if it is welded or a two-part ridged epoxy. On my 310c the hydraulic reservor tank cover plate is epoxy from the factory...cracked, and now water is in the system.

 

[Ando]

So is it actually a crack, or just the filler/paint that came off??????
If you're unsure, I'd suggest getting some soapy water, pressurise the tank with an air hose (just stick it in the filler neck with a rag to help seal it) and brush the soapy water on the "cracked" area. Only minimal pressure is required to show a crack/bubbles (2-4PSI)

 

[RobVG]

I'm not recommending anything but I had the same crack and situation on our sk. Mig welded it with no problems. Tank was low but not drained. V'd out the crack but not deep. No more cracks.

 

[dcdarby]

Just empty the tank and weld. u shud b fine

 

[Glen1978]

you dont wanna empty tank you wanna full tank.....as full as you can get it. Empty tanks are full of vapors.....vapors ignite. Fuel doesnt......well not as well. V it out and use a MIG. Stick welding is old school.