Rusty Rear O2 Sensor Removal Inquiry

Hey All,

New member here, first time post. Thanks for having me.

Limited experience and necessary arsenal of tools for mechanical work, so bear with me.

2001 Tacoma 2.7 L

Replacing downstream O2 sensor, running into the expected New England rust on the threaded studs/nuts. With some research it looks like some combination of PB/paraffin wax, heating etc should hopefully remove the frozen nuts. (Picture attached.)


My question is - is it worth (carefully) removing the nuts without snapping the studs and buying the die kit to rethread the studs? Presumably I'd have to rethread to a smaller stud size? Would you recommend removing/retapping with new studs? Or am I looking at a complete new section of exhaust?

-Or-

Fold and bring it to the beloved exhaust guy. I'm hesitant to spend the money, mostly because the money doesn't exist (maybe you can relate). But realistically it's my daily driver and I rely on it for work, so dismantling the exhaust system is maybe not a good idea. Wish I could weld!

Thanks!

 

I have heard mixing Acetone and automatic transmission fluid 1:1 is one of the best ways to penetrate the corrosion. People say they don't mix well but let it sit and mix it some more. I would try and wire wheel as much as you can, then apply the mixture and try heat. It looks like its going to be option 2 but worth a try.

 

I did hit the studs and nuts with a wire brush to remove all the flaky rust to get a better view then I carefully cut the nuts in half and finished splitting them open with a cold chisel. Then I cleaned up the studs threads with a wire brush and installed the new sensor. Put a drop of antiseize on the threads before screwing the new nuts, they'll be much easier to remove next time

 

I know what I would do install a new bung new studs and be done

If the nuts come off without breaking the studs not enough material left on the studs to get nuts on

Till your done messing around I can have it all finished

 

Ok interesting. Would you recommend multiple applications of the Acetone mixture? Letting it sit overnight?

 

Installing the new bung would be a weld job, right? And what about rethreading the studs to a smaller size?

 

I would try and get the nuts and studs both out with whatever combination of heat/penetrating fluid/wax works and just replace them

Edit: make sure you are heating with a torch before putting wax on it (any wax will work) the heat will melt the wax and suck it into the threads. That’s my go-to for exhaust work

 

Yes multiple applications and for sure let it soak in over night. What Onakat mentioned ^ would be a good option as well.

 

I have never tried threading smaller threads on a rusted stud .

try see if it works.

You still need to get the nuts off without breaking the studs.

I have tried every way

Best of luck

 

i am curious why the rest of your pipe to the muffler looks so 'clean' compared to this part?
I just had my oem exhaust from the cat back replaced after 22yrs of midwest winter weathering and it was not in this good of shape as yours looks (the pipe not the sensor hookup you have pictured) the mechanic that did this work for me did not mention it was not looking great, he just had a difficult time trying to get it off the cat!