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How to remove stuck bolts @ catalytic converter

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Nov 22, 2020, 1:56 PM

Post #1 of 3 (657 views)
How to remove stuck bolts @ catalytic converter Sign In

1996 GMC K1500 5.7 V8 200000 miles

I cant for the life of me get these bolts unstuck. Does anyone have an tricks, tips or advice? I got the ones off where the cat pipe meets the exhaust manifold with a 1/2 impact wrench at 90psi. The same wrench at the same setting wouldn't budge the bolts where the cat meets the muffler. In reading the manual the impact wrench says that any hose longer than 25 feet will see a performance reduction. My air hose is 100 feet long. Could that be an issue or are these bolts which have been on there since 1996 just known to be that stubborn?

Hammer Time
Ultimate Carjunky / Moderator
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Nov 22, 2020, 2:16 PM

Post #2 of 3 (653 views)
Re: How to remove stuck bolts @ catalytic converter Sign In

90 PSI isn't enough to do anything. My gun runs at 175 on 3/8" hose.

You need to heat the nut red without heating the stud that much so you need an oxy-acetylene set.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 22, 2020, 3:26 PM

Post #3 of 3 (641 views)
Re: How to remove stuck bolts @ catalytic converter Sign In

Ha - Oxy/Acet* = "My Blue Wrench" one size fits all when glowing hot. You do need speed heating just the nut (goggles please) can see the stud isn't quick switch to waiting socket or good box wrench ( 6 point helps not round it up) maybe able to reuse it? One turn your air will do the rest.
Use that silver "anti-seize" stuff (brush in cap) insane high temp grease it will never be an issue again.
If the nasty happens and it snaps off I'm pretty sure those are like wheel studs can punch them out for new or very hard rated thru nut and bolt at worst a "carriage" style if no room IDK if those come as hardened grade though?
* > If you've never used those practice on some junk thing out of harm's way. For a first time have someone around they are wildly dangerous so not near anything flammable even a blob of grease will flash into flames!

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