J-B Weld on mufflers

My pickup truck has a heat shield mounted below the muffler, and the spot welds on one side seem to have broken free. The shield is flapping in the breeze right now, and I’ve been exploring ways of re-attaching it.

One option is going someplace and getting it re-welded back on. Estimates for this seem to be in the $20-$30 range.

Far cheaper, if it would work, would be something like J-B Weld. I’m pretty confident that it would work for this, save my concern about the temperature. Their list of uses includes cracked engine blocks and cylinder heads, but I’m thinking for some reason that they don’t get quite as hot as the muffler (to say nothing of the catalytic converter).

The makers claim that it’s good up to 500[sup]o[/sup] F. I’m not sure how hot exhaust components get. Does anybody know whether a muffler is likely to exceed that temperature?

I think there’s a high-temp version.

on a multi day hiking trip, I broke our only lantern globe. I used JB Weld to repair it. It worked for our purposes but a odor was noticed when the lantern was used. I don’t know what would happen if I continued to use the lantern - either the odor would stop and it would be stable or the stuff would just burn off. - sorry not much help - but maybe look for a high temp ‘weld’ as mentioned above

Dude, the exhaust gas temp should be somewhere right about 1500s at the downpipe if your engine is running correctly (not too lean, not to rich). This will be considerably cooler past the catalytic converter, and much cooler than 500 by the time it hits the muffler, but still too hot to touch.

Go for it.


I have used J-B Weld at work, mostly to repair striped threads on parts of the printing press I operate with less than good results.
It seems to be OK for temporary patches but not a permanet fix.

Well, first, you feel feel damn lucky that your cylinder head and block never come close to appraoching 500 F.

That having been said, while in theory JB Weld may work, due to the high temperatures and movement of the exhaust under operation, I would bet that you might get in a situation of having to reapply it several times. It might be a case of “the cheap person paying the most” in terms of time and frustration.

You could try buying a MAPP gas torch from Sears for about $35, learning how to use it, and welding it yourself. And then you have a cool little oxy-acetylene torch to cut, melt, weld, and burn things with. :slight_smile:

Of cour’se there’s always the alternative: Baling Wire!

Thanks, guys!

As an update, I tried J-B Weld last night. I tacked the heat shield on in the two places where the welds had been.

They recommend letting it cure for 15 hours, but the logistics of that proved unworkable, and I only let it sit for 11. When it got hot and thermal expansion did its evils, one of the “welds” broke.

Instead of wildly swinging about and banging the muffler, the heat shield now vibrates loudly at certain engine speeds.

Tonight I’m going to try re-doing that weld, and I’ll let it sit for at least 15 hours. If that one fails (I give it about 50/50), I’m going to get some of that muffler patching tape/strap stuff and tightly wrap it - I think that might work.

Failing this, I may take Anthracite’s advice and “borrow” some welding stuff from my department’s machine shop…

You know, when it’s all said and done, you’ll probably end up spending the 20-30 dollars on “MacGyver” fixes.

Just get the damn thing welded and be done with it.

JB Weld is amazing stuff. I fixed the motor mount on my old Suzuki Intruder with that stuff. Lasted until I sold it.

Anthracite, not meaning to nitpick, but couldn’t the exhaust manifold get hotter than the block/heads? I have seen footage of some engines under test on engine stands that the manifolds actually glowed red/orange. They would be hotter than 500, correct? Not saying Joe Blow in his truck is going to have glowing manifolds (or at least shouldn’t) but they would still be hotter than the rest of the engine, wouldn’t you think?

I think we have crossed signals here. All I said was that the cylinder head and block would not get close to 500 F. And as to the OP, he is operating near the muffler, which is an awful lot cooler than near the exhaust manifold and catalyst, both of which see temperatures like Homer posted about. While the exhaust manifold may be 1500 F or so, the water jackets in the cylinder head and the exhaust manifold insulating gaskets should keep the temperature down significantly from that. Yes, you may see a high surface temperature right there. In which case, JB Weld would not work for that particular repair application. But no one would really consider doing that IRL IMO (YMMV). (too many acronyms here…)

FTR, I have seen exhaust manifolds that glowed a dull orange in an engine that had serious ignition retard (10 degrees after TDC) and was driven too hard - scary stuff.