Mine was like that when I bought it and I took it to the muffler shop. He double nutted it and it didn't sound as cool any more. When it unloosened again, just like yours, I kept an eye on it and it stopped unwinding back at the same spot. It sounds cool again now and has become part of it's "personality". Just like the manifold over pressure, squeaky springs, non-working tach back light, coat hanger muffler support, etc. I don't have to drive it to work though. And my gas mileage has always been 100 miles per tank. Our new 2012 Rubicon only gets 16. But it has a bigger tank!

 

To figure out the size, pull what you have and take it to the Hardware store, compare it to what they have in the various bins and get a match. Also get a bolt for it. Threadlocker Red the stud into the block, then torque on the nut. Should be done at that point. When I replaced my exhaust manifold, I purchased a new hardware set. NAPA had an "Exhaust Manifold Mounting Kit" PN 600-3243 which only had seven of the nine 3/8-16 X 1 1/2" bolts, but it did have the 2 studs and I got the other 2 Gd 8 bolts at the local hardware store. Kit was $14.53 here. The 2 studs on mine had an E torx head to them, but you can easily lock two nuts together, use that to torque the stud into the block if you go with just a standard stud, then unlock the nuts and it's in place. If this arrangement does not allow you to adequately torque it into place since the exhaust flange is there, then get a longer stud, lock it in, then saw off the excess or just leave it ladat. Threadlocker Red and it won't be working itself out any time soon.

 

Threads are 3/8"-16, the studs should be about 2" OAL (the screws should run about 1.25")

I don't recall the number, but there's a grade of LocTite that is formulated to not break down when subject to exhaust head - 27-something? It's roughly equivalent in strength to #242, and it works well. MRO or industrial supply houses should have it.

If you're careful, you can also round off a punch and deform a couple of threads that screw into the head, but screwing the stud in afterwards gets more difficult (not impossible, just difficult.)

 

Thanks all - I'll look for a 3/8"-16 x 2" or longer stud and be sure to use the right loctite. I suppose I could have pulled the stud and just driven the YJ to the local Autozone/O'Reilly's - it's not like it would have leaked any worse.

My YJ definitely sounds more aggressive with an exhaust leak, but when it's at the manifold the fuel injection likes to dump the fuel (even the OEM carter did this). I tend to normally get about 14-15 mpg around town when everything is up to par, but with manifold leak it dropped to about ~11 mpg.

Thanks again.

:cheers2: