Replace the tank.
The gas tank on my 83 rabbit is leaking. From the very bottom. Its like someone poked 3 pin size holes it in. I tried draining it and using a gas tank patch kit but it failed. Its on the very bottom so some leaked out and ****ed it up. Next I'm gonna try some jb weld. Anyone have another tips? putting a new one in looks like hell.
You can try JB Water weld. We've had that on our diesel tank for probably 2 years now with no issues.
Another reason to replace the tank is because of the inevitable disintegration of the plastic baffling box inside the tank. This leads to the right- hand- turn- starvation syndrome, when the fuel pump intake runs dry on a turn with a low fuel level tank.
Spectra 4B is the common replacement tank. It has baffling, too. There is more information in the forum FAQ/DIY sticky thread.
I just replaced the tank in my 1.6D. (same tank as gas). i got the tank off ebay and it had free shipping. $80 total. i am very happy with the new tank and am now modifying the old tank for wvo use. por15 makes a tank repair kit but you have to take the tank out anyway to use it. (plus i think it wont work with that plastic thing on the inside.) Anyway, get two good jacks on the back end, drop the axel, take the brake lines off.... sigh... yea- i never wanna do it again but i am very happy that i did. its hot as hell here in MN right now man, have on hand.
Replace it... Patches are temporary junk.
the only other solution is to find a place that will rinse it, fume it off, and braze it.. For the hassle and cost it'd be best to replace that internal rust prone 30 year old piece of crap for a bit more. $80 is cheap!
the biggest hassle is disconnecting the rear axle and brake lines
but nothing that will destroy your car obviously....