I'm tired & couldn't think of anything else

[DrPizza]

Just had a pinhole, right under one of the straps. Removed the strap, scraped it clean, sandpaper, etc. But the gas was at that perfect level where it wasn't really leaking any more, but just sort of weeping through & wetting the surface. Washed & dried the surface with rubbing alcohol (screw the little pad, I used some soaked paper towels.) But, I wasn't 100% sure that the epoxy was going to hold. The hole looked like somehow a little pebble got lodged between the strap & the tank and managed to wear a tiny little hole into the tank.

Regardless, the rubber spacers for that strap were shot, so I had to do some brain-storming.

Great Stuff foam.

Since the entire area had been wire brushed & sanded, I reasoned that I probably removed much of the galvanized protection. And, I needed spacer. So, I cut a 3" wide strip of plastic from a milk jug, duct taped that loosely in place, and filled between the plastic & tank with great stuff foam.

And, I got to thinking - how good would that stuff be as an undercarriage coating for things like the gas tank? And, could the great stuff foam seal a pinhole gas leak all by itself (I wasn't about to try. I used the epoxy stuff that came in a kit made for repairing pinholes in gas tanks that my wife picked up for me; pretty much identical to JB Weld, plus a small piece of sandpaper, for twice the cost.)

 

[Bignate603]

I wouldn't try great stuff where it could contact gas.

What car do you have though? I got a junkyard gas tank before for ~$50. If the car is old enough to have some in junkyards the tanks are pretty affordable.

 

[DrPizza]

The patch was pretty trivial; the metal cleaned up very nicely; very little rust. But, whatever got in there destroyed the rubber where the strap bends around the corner of the tank.
AFAIK, one great stuff cures, the vast majority of solvents won't do anything to it. I didn't use it as a sealant - that's the question I was pondering though - I wonder if it actually would seal a tank. I use it for the layer between the metal strap and the gas tank.

 

[iamwiz82]

Just poking around Dow's site, I found this:

How do I get foam off the side of my house?
If the foam has not cured or hardened, use acetone or fingernail polish remover (with acetone). There is no solvent that will remove cured polyurethane foam. Remove as much as possible with a dull scraper or a hacksaw blade and then try scrubbing the remaining film with a non-abrasive cleaner. If that does not work, gradually move up to more aggressive means including sanding, sandblasting and repainting.
Warning: When using acetone on surfaces such as sidings, always test a hidden section of the surface to make sure that the acetone does not discolor the surface.

http://greatstuff.dow.com/literature/index.htm

 

[boomerang]

Great stuff does not hold up under UV. This is probably not a factor in this case.

I had a trunk of a tree split. The tree is leaning at an angle. The tree guy put a threaded rod through it with washers and nuts on each end to help hold the tree together. He suggested I fill the crack with Great Stuff to keep the water out. First time the sun hit that stuff it started breaking down at an alarming rate.

Good repair, bad advice.

 

[iamwiz82]

Originally posted by: boomerang
Great stuff does not hold up under UV. This is probably not a factor in this case.

I had a trunk of a tree split. The tree is leaning at an angle. The tree guy put a threaded rod through it with washers and nuts on each end to help hold the tree together. He suggested I fill the crack with Great Stuff to keep the water out. First time the sun hit that stuff it started breaking down at an alarming rate.

Good repair, bad advice.

Great Stuff has a UV resistant version as well, it's more expensive, though. I believe it's call Pond Foam.

 

[boomerang]

Originally posted by: iamwiz82

Originally posted by: boomerang
Great stuff does not hold up under UV. This is probably not a factor in this case.

I had a trunk of a tree split. The tree is leaning at an angle. The tree guy put a threaded rod through it with washers and nuts on each end to help hold the tree together. He suggested I fill the crack with Great Stuff to keep the water out. First time the sun hit that stuff it started breaking down at an alarming rate.

Good repair, bad advice.

Great Stuff has a UV resistant version as well, it's more expensive, though. I believe it's call Pond Foam.

Ah, well this was IIRC fifteen years ago. Even if it was available then, he didn't mention it.

Good to know.

 

[lurk3r]

Virtually any auto parts shop will have a gas tank repair kit thats at 2 part epoxy similar to the Billy Mays stuff, just make the hole a little bigger, mash the epoxy in your hands and push it thru the hole. It comes in a strip that looks like taffee. Your only concern is getting one that will set in gas. Shouldnt cost more than ~$6.

 

[DrPizza]

That's what I used, lurk3r - a two part epoxy that you mash up in your hands. I didn't make the hole any bigger though. It's supposed to set up in gasoline, but I just had slight doubts. So, in addition to that epoxy, there's great stuff foam in a layer between the tank & a big piece of plastic from a milk jug (to keep the stuff from dripping on my hands - I know how hard it is to get it off), and the milk jug was held up with duct tape - pink duct tape. After the foam set up for about 15 minutes, I replaced the strap that holds the gas tank up. The strap is now holding everything in place against the tank. I had my son take a glance at it when I dropped the car off to him... "ohhhh myyyyyy Goddddddd."

But, it saved me from driving 1 1/2 hours to his college, driving another 1 hour plus to where there was a concert, waiting til the concert was over, driving him (and his girlfriend - if he wasn't doing this because it was his girlfriend's favorite band, I'd have told him to just sell the tickets to someone else) back to his dorm, then 1 1/ 2 hours to back home. He called to let us know when he was back to his dorm - nearly 1am. So, I'd have been out til 2:30am, then would have had to get up at 5:30am for work. And, both of my sons will be using that car this weekend, since it has a hitch on it & they'll need to pull a trailer.

So far, it's not leaking. If it does start leaking again, then I can take the time to completely remove the tank & even consider just replacing the tank, etc.

 

[lurk3r]

I've patched tanks before, but without the little plug actually going in to the tank your patch can slide around/off. A screwdriver sized hole, or slightly smaller made all the difference in the world for me. It does help to jack the car up on one side so you're not working in gas.