Catalytic converter replacement fun

That looks like a huge pain to deal with under your car... If I were you I'd by an exhaust header gasket, pull out the windshield wiper assembly and metal cover it sits in and remove the exhaust manifold so you can resolve that busted bolt in a vise rather doing it from underneath...

 

Option 1, see if there is enough sticking out the back side to grab it with vice grips and screw it UP-wards. Might need to heat it first.
2, drill out the bolt; either drill small and try to tap it and save the threads, or drill large and just use a nut to hold the new spring bolt.
3, have some one weld a nut to what's left then use that to unscrew it.
4, use a sawzall or cutoff wheel to make a slice through the edge of the flange and completely through the bolt (from 3:00 towards 9:00 on your pic). Once the bolt stub is split you can collapse what's left and remove it. If the cut is slim, then the remaining threads should hold a new bolt. Or use another nut behind it.

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Drill a pilot hole and then use an extractor bit, the kind with aggressive reverse threads?

It’s screwing into a weld-nut on the far side?

 

omg thats a nightmare. What idiots.

yeah I think the mani is going to have to come off. Unless your taking it to a shop your laying on the ground under it which makes dealing with it connected to the mani 10 times harder.

 

For the mani Have to take the windshield water dam off by removing the wipers and unscrewing a few things gives you a little more room to get at it.
I cannot remember anyone on this site removing the mani. The sob’s.

all I can recommend is use quality sockets not harbor freight pos stuff.
truly a nightmare I feel for you,

you may want to try mr man guys advice first if you can I like it the best
If you F that up the mani has to come off anyway.

wear protective glasses there will lots of metal flying around

 

Oh your a welder? Alright!

Hard to get to but if you can weld a nut to the backside of that stub? Hopefully unscrew it out. Good luck thats such a bastard thing to do to someone cut that bolt off flush...my god.

 

That makes sense... May your welding skills be way better than half-baked once you're done. Make sure to double and triple check how solid your jacked up car supports are / super extra safe with redundancy, same with welding gear!

 

One bulletproof redundancy is something thicker than you and solid, under the car with you.

 

Practice some first. This can be a huge PIA for any weldor- even one with experience and a lift. Get some bolts and nuts - figure out the technique when it's out in the open and you are welding down. 1 way to do it is to get a big thick washer over the stub then weld it. Then weld a big nut (say a 1/2 inch) to the edge of the washer. Be prepared to do it several times because it can break off.
Second way to do it is to carefully put a small blob of weld on the end of the stub, then hold the nut onto it and add more weld to the center.
Before welding on the car it is a good idea to disconnect the 12V battery to leesen any chances of damaging the car's electronics.

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Also realize that if you're doing this on jackstands, then you are going to be in a very poor position while you work- bad access to reach the work with both hands, difficult to see with a helmut on, and underneath where all the sparks and spatter will fall.
It can be done but be sure to have good protective gear on.

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i use reverse drill bits personally usually fastener follows...

 

I ran into the same issue. I used my
M12 12V Lithium-Ion Cordless 1/4 in. Hex screwdriver as a drill, and I drilled a hole in the center with a 5/32 in. bit about a half an inch deep. I then used the 3/8 in. bit to remove the mushroomhead portion of the bolt. Then, using the 5/16 bit, I bored into the hole just past the opening; so, I was probably only a 32nd of an inch into the hole. Then, I used a 3/16 to bore completely through bolt, I then bored through with a 7/16, and lastly with a 1/4 bit. Finally, using a no. 3 bolt extractor, I was able to spin it out.

It was trial and error, and it took a lot of strength. I have really long arms, which helped with this. This method may not work for everyone. If I had to do over, I probably would have gotten the next biggest bolt extractor size (no. 4?) and bored through with a 5/16 bit. The more you bore, the easier it will come out. *The catalytic converter I purchased came with 2 nuts for the main bolts. So, if you damage the threads on the manifold, just put a nut on the backside. Hope this helps!

 

Totally agree... I can go work 5 hours of extreme hard labor in someone's garden, but a hour or two under a Prius on jack stands dealing with a cat swap that didn't go as planned can make me even more sore the next day. And that's not even doing the welding part.

 

using a welder in this scenario will only take less than 5 minutes. The heat from the welder loosens up the bolt if it's rusted stuck. When I replaced the stolen catalytic converter on my Volvo xc90, one of the exhaust bolts broke its head. I was thinking that it's going to be a long day dealing with this bolt (the exhaust manifold area is not fun). Luckily I got a stick welder and has some sticks lying around (last one), welded a nut, let it cool down and I just loosen it as smooth as butter.