removing stuck O2 sensor

Not sure if anybody will be able to help me with this, but I figured if nothing else y'all will get a kick out of the photo.

-for context, the photo is after I sprayed the metal with rust dissolver and scrubbed it down. It's currently basting in PB blaster
-the base of the sensor ("B" in the photo) is totally smooth. Almost doesn't even feel like it was stripped, it just feels smooth. My sensor socket just rolls over it.
-I've felt for them and I'm pretty sure there are no nuts on the bolts. Think its being held in by pure spite and rust.

I honestly don't even know where to start with trying to remove the sensor. Can't get a grip with anything at "B". Would it be possible to grip the sensor at "A" with pliers and twist it out? I haven't tried this yet in case it just crushes the ferrule and I'm stuck with a broken O2 sensor. Right not it's nothing super serious, just a P0136. All the videos I found on youtube about stuck 02 sensors were still working with sensors that actually had a head to find purchase on. There's nothing here to even grip. I would be hugely appreciative if anybody has any suggestions or has run into a situation like this, but, if not, hopefully you'll at least get a good laugh.

 

Both a and b are attached to the plate with the studs sticking through it. The rusted nuts look totally dissolved but not gone. I highly recommend a sharp cold chisel to get the remainder of the nut around each stud so you can pull off the O2 sensor.

You can then clean the threads of the studs or just twist them out and replace them.

 

Thanks for the reply! I'll try the chisel and let you know how it goes.

 

There should be two nuts screwed onto those studs holding the sensor on. If the cold chisel doesn't work, I would try a reciprocal saw with a sharp metal blade on it to cut a slot into the nut (don't cut the stud or even cut into it). Just cut into the nut until you can get a medium sized screwdriver in the slot, then twist the screwdriver to spread the nut apart. Then you can pull the shredded remainder off.

 

That looks like some of my luck. Thats a tough one there. I’m sure you don’t have much room to work with but if the cold chisel doesn’t work see if you can get a small end die-grinder in there, you may be able to cut the nut enough to chisel it off the stud. If you can get the old nuts off you may be able to put a thread die on the studs to salvage them. If you wind up having to replace the studs then you may have to put some serious “heat” on them to get them out. Just my 2 cents but be careful and don’t twist the studs to where they break off flush…then you gonna be left with drilling and tapping for the new studs. Good luck, hope it works out for you. Let us know how it goes.

 

FYI, the flange on the o2 sensor is stainless, so whatever corrosion is going on, it's emanating from the exhaust pipe side of things. If you end up snapping off the studs, it looks bad enough that it's going to be a large headache to drill and tap the mounting flange. I'd almost be half tempted to (if you have a welder that is) weld in a standard threaded stainless steel O2 sensor bung into the exhaust pipe. Just like how the front o2 sensors are threaded in. A bung with a super wide flange like this one makes it super easy to weld onto a pipe. https://www.summitracing.com/parts/...GgdoTsMQjASZrjhm6IRS4daGjCg7Vk5RoC-GIQAvD_BwE

 

I've had luck with cutting a slit into the nut on the stud with a stainless dremel cutting bit. Like said above don't cut to too deep into the nut where the cut goes into the stud. Then use a chisel or slotted screwdriver to break the nut off the stud.

 

Might try a nut splitter.

 

Wire brush to knock off the excess rust, then slather the area surrounding in Naval Jelly and let it sit for an hour or two. Rinse into a drip pan so you don't acid-etch the concrete.

Repeat until you can clearly see what you're working with.

I can't recommend getting a cheap nut extractor set. PF did a great review on them.

https://www.youtube.com/watch?v=EWLxzuDMuhk​