View Full Version : exhaust manifold- rusted nut

07-25-2007, 12:54 PM
So I'm doing headgaskets, and the only thing left to do is to take the exhaust manifolds out of the car. the passenger side came out fine, but the driver's side is not going well. The nuts that connect the manifold to the downtube are very rusted. I tried mapp gassing it to cherry for 5+ min, and I tried soaking it in pb blaster for days. Eventually, it just rounded when I used real torque.

Because of the 90 deg. cat and the shape of the bracket, I can't get a cut off wheel to the stud or an extractor to the nut/stud. I suppose I could cut the downtube, but not only is that a ton of work with the tools I have, I still want to use the stock downtubes for now.

My next crazy idea is to try high strength locktite on a cheap socket.

Anyone have a better solution?

07-25-2007, 01:17 PM
when I did the head gaskets on my 90, I left the manifolds connected to the exhaust pipes and just pushed it all out of the way.

See if you can get a die grinder or dremel up in there with your hand. It'll take a while but you should be able to grind the nut in half getting it to break off.

Then when you get the manifolds out you may want to take them to a machine shop and have the old studs pressed out and new studs pressed in. I wish I had done that with my manifolds on the 93, but just didn't have time.

07-25-2007, 01:32 PM
take some sandpaper and sand as much of the rust off of the joint between the bolt and stud as you can, then hit er with some pb blaster and wrench that motha off. ;)

07-25-2007, 02:16 PM
I think in this case sandpaper and wrenching are lost causes- been there, done that. PB blaster is great stuff, but then again so is mapp gas., and neither worked. the nut is stripped worse than I've ever seen. Normally, vice grips would work well, but there is no way to get them around the body of the nut as It is recessed.

The first suggestion seems like a good one, but it will be a very tight fit with a dremel. i'll look into borrowing one perhaps. Thanks!

07-25-2007, 02:27 PM
You might try some of these:

07-25-2007, 03:19 PM
Or try one of these.


07-25-2007, 04:49 PM
You may be able to salvage the mess with a small "sharp" chisel, clamped in some Vice Grips.

07-25-2007, 05:16 PM
Oh, by the way - I had a heck of a time with those nuts and studs on my old '89 Base model. That was the single hardest part of changing the head gaskets. I actually hacksawed through the stud between the manifold and the exhaust flange. Then I held the manifold in a vise and drilled the entire stud out. I used new bolts and nuts to refasten the downpipe when I was all done. it worked fine, although I would have installed a new stud if I knew then what I know now.

07-25-2007, 05:59 PM
I ran into the same problem when I did the headgasket project on my titanium 89. Fortunately, the studs twisted off on those that didn't come apart, so it didn't hold up the project. While the heads were away at the machine shop, and I had some down-time, I used a torch and vise-grips to remove one stud, and drilled out the other.

I heli-coiled the threads to an SAE size, and installed new studs and brass nuts. You can buy the stud/brass nut kits at the parts stores in the HELP! line. The brass nuts are the hot ticket, because they can't seize on the steel studs. I've done this trick on all my cars, and have never had a stuck flange nut since...


07-25-2007, 07:51 PM
to disassemble or cut the downtube and remove the complete assembly from the car. You can do anything you want on a bench to remove the offending parts at that point.

The only other suggestion I have is to get a nut/stud remover socket. They are designed to do just what you need, knowing the nut isn't going to be reused. The more toque you put on it the more it bites/cuts into the nut to remove it. It will come off or it will break!

07-25-2007, 09:58 PM
Get a socket to fit good then use an impact wrench and be done with it.

07-26-2007, 02:52 AM
Get a 12 point socket thats just a bit to small and hammer it on, then use your breaker bar and loosen it. It has always worked for me, even on locking lug nuts.

07-26-2007, 02:31 PM
Thanks for all of the suggestions. Some of them won't work because of the tight space involved. This is the 90 deg. cat, remember! I can barely get a socket on at all, much less hammer a smaller one on. Also, it is totally rounded, so an impact gun won't do anything.

I've decided to follow the suggestion of using a dremel and small cutoff wheel to cut the stud. I will also replace w/ brass hardware as per one of the suggestions (Brilliant!)