Leaking Gas Tank

[jthiessen]

There appears to be a leak in my gas tank..

When I bought the bike there was a good ol' wad of silicon around the mounting tab at the back of the tank. Didn't know if it was because the mount tab had broken loose and the PO was reattach or if it was leaking. Year later my bike started to always smell of fuel and the silicon all fell off. It revealed a nice track of what appeared to be JB weld, which also came off when I picked at it with my finger.

So, there is a leak. How do i fix it? I heard to weld a tank one must (obviously) purge it of any fuel vapours. A buddy said their shop will do the electrolysis treatment to clean the tank out. I've also seen people use solder to repair holes. Others say just use a tank liner - though I feel that one isn't as permanent.

Thoughts?

 

[rshutchinson]

Having it TIG welded would be best and due to the area it's in you should be able to get away with not having to worry about the paint. Just tape it off afterwards and get some paint that is close to the color of your tank and go over that area afterwards.

With that said, I've used lead from wheel weights to fix a hole. Dent the hole with a ball-pean hammer, clean the area of paint, clean with flux, clean with flux, clean with flux, then melt the lead in an old pot and pour it over the dented hole. Then filed smooth. I don't think this method would be best for you given the location, though.

 

[BBS360]

Anything short of welding will be a temporary fix.

Electrolysis seems like overkill unless you need to de-rust the tank too.

The shop that lined my tank welded in a drain bung on the side opposite the petcock. Not sure how necessary the bung was but they dipped the tank in a chemical cleaning vat that took care of any gas fumes.

Should be a shop that can clean the tank and weld it all in-house.
The shop that did mine was a radiator/industrial equipment repair shop. Might have something similar up there.

 

[jthiessen]

Follow up Q:
What kind of fluid would work best to pin point the leak? I know the general area (around the mounting tab) but before I weld the tank I would like the confidence of knowing the exact location of the leak.

I figure water would cause some rust issues... Would vinegar be better? I have no idea!

 

[rshutchinson]

Vinegar will work amd so will water if you flush it out afterwards and fill with fuel afterwards.

However, I'd plug the filler cap, and put petcock on prime. Use soapy water on outside and blow into tank through the petcock. Use a long hose so you can look around the tank St the same time. The soapy water will bubble up where the holes are. I say this because you can test that you sealed the holes up afterwards to make sure without having to fill and empty the tank multiple times. Sometimes when you plug a hole you may open up a small one beside it or might not have even plugged the original one.

You can use compressed air but turn it way down, like 1 psi.

 

[jthiessen]

However, I'd plug the filler cap, and put petcock on prime. Use soapy water on outside and blow into tank through the petcock. Use a long hose so you can look around the tank St the same time. The soapy water will bubble up where the holes are. I say this because you can test that you sealed the holes up afterwards to make sure without having to fill and empty the tank multiple times. Sometimes when you plug a hole you may open up a small one beside it or might not have even plugged the original one.

You can use compressed air but turn it way down, like 1 psi.

Oh wow that is a great idea! Thank you, that will save a lot of time!

 

[jthiessen]

Did as rshutchinson said, and found the leak (after popping my ears because I forgot to open the petcock). It was along the plate where the mounting tab is connected, just as I suspected.

Going to bring it over to an old plumber friend. He said he will purge the tank with truck exhaust and do a bead of lead solder around the leak.
Hopefully everything goes well!

 

[jthiessen]

Solder was successful...I think. We didn't explode. Used 50/50 solder. Won't really be sure until I fill it up!

 

[jthiessen]

It would appear I have some flash rust inside my tank now.
I've read you can use vinegar to get rid of the rust, dump it, then spray in some WD40 to prevent more...
Any experience?

 

[Wolfe_11B]

yeah if it just flashed over it will go away easy with vinegar. Don't wait any longer though, it will just get worse. I kept mine in a garbage bag with a desiccant pack and it kept the rust away for a very long time. I guess you could use wd40, but it won't last too long and the rust will be back.

 

[rshutchinson]

After cleaning it out I throw a little bit of light motor oil in there and swish it all around to coat the inside. That will stop rusting. Then you can rinse it out again (with some gas, just swish it around and drain, repeat a few times) when you're going to use it.

 

[jthiessen]

light motor oil

What is considered Light Motor Oil?
Also could I hit it with vinegar then put the gas back in it?

 

[Wolfe_11B]

Putting gas back in it is the best thing you can do

 

[rshutchinson]

What is considered Light Motor Oil?
Also could I hit it with vinegar then put the gas back in it?

5w20.
Definitely you could. I was just stating that rather than using wd40.

 

[jthiessen]

Okay thanks for the info.
Unfortunately I think I let the rust sit in there a bit longer than a should've. I just noticed it and I was working on the tank three days ago...I will let it sit full of vinegar for a day and see what happens.

I guess plan B would be electrolysis.

 

[BBS360]

Electrolysis is messy and not easy to do a thorough job with as the effect only happens within line of sigh of the electrode.
Vinegar should work. After that I'd go to a commercial rust removal product. Metal Rescue or others.

 

[jthiessen]

Looks like the vinegar helped, but didn't clear out all the rust. Looks like I will be picking up some commercial cleaning product...

 

[BBS360]

Does it still look like reddish/orange rust or have the rusty bits turned black?
Depending on how bad the rust was it might not actually come off but if it's black it should be neutralized.

 

[jthiessen]

Still orange. i guess i will pick up two of those jugs of metal rescue... not my first choice to spend $70....

 

[BBS360]

Just one works if you don't mind sloshing it around for a little while.
It'll still be good to derust plenty of other parts too.