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Rusted exhaust bolt

bolt is rusted. not broke off flush, yet. how about if i cut/slit where red line is to make flange possibly release its grip on bolt? i think the remaining flange is enough to hold pipe clamp. or is there another way to get this bolt out?IMG_3485

They make a tool called a stud remover.


Disc shaped wire brush in drill. Clean lower threaded end as much as possible. Apply B’laster PB several times. Heat edge of flange (red line area) to expand flange. Use small pipe wrench on top section of stud to turn it out.


I used wire brush. Mappgas torch on flange. Melted wax on threads. No budge. Do have generic wd40 ish stuff. Pb is better? Effective?

Often Oxy-Acetelyne is necessary. I have found that heating cast iron until I hear it begin to click almost always loosens frozen fasteners.

And parrot beak pliers often work better than a pipe wrench.

It looks like you have the part out of the vehicle.

Know anybody with a welder?


Because this exhaust manifold is out of the car it shouldn’t be that hard to remove.

I had a friend…yes I do have a friend…come over the other day with the same thing.

I heated the manifold to a yellow heat and used a stud remover like @Tester eluded to.

I got one out but had to drill and retap the threads in the second one.

The other method is to find a nut that fits over the end of the stud. Don’t worry about it threading onto the stud.
Then weld the nut to the stud.
You will still have to heat it to a yellow heat, then get a wrench on the welded nut and break it loose.

If you do get it broken loose…lube the threads to make spinning the stud out a bit easier.

One idea; I usually keep a vehicle quite a long time. If I think that at some point I will have to remove the exhaust bolts in the future…I replace the bolts with Stainless Bolts. They will never weld themselves like that and you will easily remove them in the future.


Never install stainless steel hardware in components that are carbon steel that gets extremely hot.

The stainless steel expands/contracts at a different rate than carbon steel.

This causes the two different steels to seize to each other like they’re welded together.

Ask anyone who’s ever worked with an engine dyno with thermocouples mounted in the exhaust.


That looks like a tough one. I’ll use the term “one” rather than what I actually say if presented with that problem… lol … I think what I’d do is make up some home-make thread penetrant. Last time I made up a batch IIRC I used 1/3 mercon 5 transmission fluid, 1/3 acetone, and 1/3 sunflower seed oil. I’d soak in in that for a few days, then use a propane/mapp/ mapp + o2/ torch and whatever wrench worked best to see if it would budge. If not, I’d cut it off on both sides with a sawzall , dremmel, angle grinder w/cutting disc, or whatever, then drill the remaining section out. I might try an EZ out before entirely drilling it out, if I was in a scientific mood. Shouldn’t be much trouble to drill it out, I doubt the stud is hardened much.

I like to cut those flush with the manifold and drill them out and run a tap through to clean it up. Cast iron is a lot harder than steel so the job is easy. That stud remover might get it out easily.

I am ready to put head on. After I fix bolt. No oxy torch. Technically it is not very hard to cut flush and drill it out as manifold is off car. Drill/ tap might be my only fix

I have found PBlaster to be very effective at times,

bolt is in exposed flange so its not buried in a blind hole such as head or block. cut flush, drill and tap. would be nice to have drill press to keep drill somewhat centered but go easy so it wont walk too far off centerpunch spot.

What they call an old guy who used to be a successful womanizer.

No comparison to wax, not even in the same universe. I have found Seafoam Deep Creep to be similar in performance to B’Laster PB if one or other not available. WD40 no better than wax or water in this application…

If you do resort to drilling, try this- center punch as close to center as possible. Drill small hole at first and only deep enough to be through flange width. Then gradually increasing sizes but well short of hitting threads of the flange. Once you have 90% removed, grasp bolt end from bottom and rotate it out. This removes most of the force on the bolt and avoids having to be perfectly centered. Heat is your friend, even if it is propane. And penetrating oil…

I still think a slit thru flange up to threads would allow you to pry or split the flange apart ever so slightly and help the situation. if you say the bolt threads are fuzed to the mating threads in the flange and there is no chance of them ever separating than maybe the slit is a waste of time. would be easy with a dremel and cutoff wheel

Instead of heating up the flange, heat the broken stud until it’s red hot and then let it cool down.

Then try removing it.

Sorta like this.


‘Rusted exhaust bolt’? What happened to the title of this thread?

Except you don’t need to destroy the flange. It’s completely unnecessary. All this discussion, it could be out already. No need to overthink it.

1 Like

had to try slit. Didn’t help