I just finished making a new exhaust system for my 97 celica. Being the dumbest person alive, i made a joint just beneath the gas tank, in the one place where there's not a heat shield. Now this joint leaks, and small amounts of exhaust burst directly onto the gas tank.

I've used a similar joint to the one below, and i've tried twice with sealant and once without. Still leaking:
http://exhaustpartsuk.com/images/SDC17494.jpg

Any suggestions? A road trip is coming up in two weeks, and if mine doesnt work until then, ill be driving my gf's mazda 2

drop the exhaust and have the joint welded then reinstall it. You could try a band clamp maybe.