Quick & dirty exhaust repair: JB Weld?

My GF's car (05 Cobalt) has a small (1.5" x 0.5") hole in the exhaust where a weld point for the heat shield over the rear axle has rusted through. Because of the shield, it's not really possible to wrap the pipe. Given how far back it is in the system - over the rear axle, maybe 8-10" before the muffler entrance - I'm thinking of just sticking a piece of sheet aluminum over the hole with JB Weld; it's supposed to be good to at least 450degF, according to the manufacturer. Is there some reason this is a bad idea, at least until spring when I can drop the exhaust and weld it up properly?

In reply to 02Pilot:

I've done it.It lasted for awhile.You are not out much if it doesn't.

On the Cadavalier I slathered the area with JB Weld, placed a patch from a tomato paste can over it, which was almost a perfect fit and heavier than a beer can, and held it in place with a hose clamp. 4 years later it was still good when I traded it in.

Hose clamps are the trick to getting it to last.

When I half ass something I do it thoroughly.

i have used a leftover chunk of exhaust wrap, a tin can, and hose clamps to fix leaks like that before..

You had me at quick and dirty

OK, so no fears of the JB Weld igniting and burning the car to the ground, right? 'Cause she really wouldn't like that. I'll throw a clamp on it and hope for the best.

No, I don't think it will burn. I used it to patch a hole poked in a muffler can on a motorcycle that gets much hotter than that muffler ever will, and it never ignited. It didn't last super long, but it's a dirt bike, which probably has a lot more vibration in the exhaust than a car.

They make muffler putty that works better, good to 2000 degrees. It is a white paste that hardens with heat. As long as you get some of it up IN the hole, it will stay put. It needs to mushroom out inside the hole for a secure patch, it won't simply bond to a rusty pipe.

In reply to pinchvalve:

I think either one will work nicely. I'd probably lean towards the muffler putty.

I looked for the muffler putty - I used it years ago on something else - but I couldn't find it in the two local stores I checked. JB Weld, on the other hand, I have plenty of. If if fails, I'll look harder.

I put JB weld on a cracked exhaust manifold on a Honda once. It didn't work (way too hot, right off the ports) but it also didn't self ignite and destroy the car. So, ya know, go for it.

Years ago I read the testimonials on the back of a tube of jb weld and it said houston municipal used jb weld to fix a gouged cylinder wall on a road paving tractor. Should be fine on a muffler haha

Wire the shield back on, slather hole area with ultra copper rtv.