Catalytic converter stud damaged

One of the 2 flange studs where the converter meets the engine is badly damaged. I tried a thread chaser with no luck. Not much room at all to get to it. I’ve also tried one of those stud remover tools…no luck… The car is pretty loud with only one bolt on the converter, any advice?

Take it to a muffler shop they deal with things like that all the time.


I see a more hands-on approach but the shop idea is better. Cut it off flush, drill it out and install a bolt.

You may have to heat the flange up before the stud removal tool will remove the stud.


maybe you can use 2 split flanges. cut the bolt flat. put one on each side of old flange and then bolt the new ones tight together.


I hadn’t realized wax could also help.
Thanks for posting this.

I’m pretty much limited to what I can do in my driveway. I have the converter off. I was able to cut the bad stud flush. Now I need to get some good drill bits and drill it out to add a bolt.

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There are also things that look like “C” clamps that substitute for a stud.

One technique I’ve used for damaged threads, find a nut that’s sized to fit the stud. Figure out a way to cut a thin, shallow slot across the threaded part of the nut. Now the nut will act sort of like a die and turning it onto the stud might clean up the stud’s threads. I brought a garbaged- bicycle back to life using this technique.

Another idea, if you don’t have a stud remover tool, put two nuts onto the end of the stud in a jam-nut configuration. Wrench the lower one against the upper. With any luck this will put considerable twisting force on the stud. Probably still need to heat the flange. If heating the flange isn’t possible for some reason, like too close to fuel, try penetrating fluid and place an ice cube on the stud. Avoid using penetrating fluid AND heat, that may produce toxic fumes. That may be why they used wax instead.

On what stud?


It’s the flange off the engine manifold where the converter bolts to…really tight.