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Discussion Starter #1
In the process of replacing my rusted-out lower cat, I broke off both of the bolts that connected it to the upper cat. I then proceeded to attempt to remove the upper cat by Dremeling off the three nuts used to connect it cylinder head, and now I'm not able to remove the upper cat from the cylinder head. The three studs are still in place and there appears to be a lot rust between the studs and the flange. I sprayed PB Blaster on the studs and flange several time over the past week and still can't get the upper cat to budge. Any suggestions on what to do now would be appreciated.
 

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Try heating the nuts?
 

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It just slides off the cylinder head - there's a metal gasket in between, but nothing should be holding it. It just slides straight off. I assume you've also unbolted the cat from the metal arm holding it to the engine at the bottom?

Here's a pic of the back of the engine (not mine):




I removed mine after I started getting a code, and both cleaned and rust-proofed it. 3 winters later it's still doing great. I did have to replace most of the bolts and nuts though.



 

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I've used both a grinder and chisel to get these off, just be real careful with the threads.
 

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Discussion Starter #6
Thanks for the suggestions. I already cut the nuts off. I nicked some of the threads on the studs in the process, so I'll replace those once I get the upper cat off. The bracket that attaches to the bottom end of the upper cat is already cracked from rust and/or fatigue, so that's not holding it. I'll take some pics when I get a chance to work on it again next weekend.
 

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The studs unscrew from the head easily if you can get a grip on the nut. They're designed so that if the nut rusts on, you can just unscrew the entire stud + bolt.
No idea how people here can do that with the engine in the car. I took the engine out of my parts car and still can't get the cat off.
 

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I actually removed mine last weekend to re-rust-proof it and did it without even getting under the car - I just reached down behind the engine. It was a little tricky to fish out the top because my cruise control is right above it.
 

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Are there nuts welded to the upper cat exhaust flange, where you attach the down pipe?

My exhaust gasket is hosed. Looking at the two bolts that attach the downpipe, the bolts that show through to the top of the flange (looking from top side of rear of engine), I can tell they aren't coming out. Those bolts are just going to snap.

I bought Dorman replacement hardware. It came with the bolt, spring and two nuts. I take it you need to remove the nut from the backside of that upper cat flange to install the new hardware. Just grind them off?
 

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Are there nuts welded to the upper cat exhaust flange, where you attach the down pipe?

My exhaust gasket is hosed. Looking at the two bolts that attach the downpipe, the bolts that show through to the top of the flange (looking from top side of rear of engine), I can tell they aren't coming out. Those bolts are just going to snap.

I bought Dorman replacement hardware. It came with the bolt, spring and two nuts. I take it you need to remove the nut from the backside of that upper cat flange to install the new hardware. Just grind them off?

Yes, the nuts are welded, so you'll probably either need to grind them off, or perhaps just drill them out a bit wider so the bolt can go through, and put the new nut on top.
 
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