Back O2 sensor studs... right before muffler worn and nuts won't thread. Solution?

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My other nuts seem to have removed themselves. I found the sensor cover hanging on one stud/bolt. (Lucky!) Can't get new nuts to thread. Tried 8MM 1.25 and 8mm 1.0.

WD40'd and wire brushed threads..... no help. They look worn on to. Not really sure how the old nuts came off? Studs are mounted in the exhaust pipe. Can't seem to find specific info/thread. If I try to chase or re-thread studs.... what pitch should I use?

Any help appreciated. Kind regards. This is my 97 FZJ80. Thank you!
 
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flintknapper

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My other nuts seem to have removed themselves. I found the sensor cover hanging on one stud/bolt. (Lucky!) Can't get new nuts to thread. Tried 8MM 1.25 and 8mm 1.0.

WD40'd and wire brushed threads..... no help. They look worn on to. Not really sure how the old nuts came off?
The old nuts may have rusted away. Seriously I have seen them deteriorate to the point that they are nothing more than some rust clogging up the threads. Or they may have come loose. Not sure how that actually happens, but I have seen several where it did.

Throw your WD40 away and get some real penetrating oil. Or better yet, mix up some Ed's Red (use the full formula). But... first, wash whatever oil may be on the studs off with carb cleaner or something similar and apply some muriatic acid to eat away any rust (and or rusted remains of old "disappeared" nuts) that is clogging the threads. THEN oil it and chase the threads. Apply antiseize with the new nuts. It will not last forever in that spot, but it will help slow rust and nut seizure.

Mark...
 
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Joined
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The correct threads are 8mm x 1.25.

I use the Dorman p/n 982-008D from O'Reilly.

Use COPPER anti seize.

The nuts on mine nearly disappeared as well, but the anti seize preserved the threads underneath the nuts.
Hey, BILT4ME. I couldn't make the Kessler Run either. Should I still use muratic acid or PB Blaster on studs, or with the Dormans cut their way back on? Thanks and good to see a friendly name reply!
 
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Hey, BILT4ME. I couldn't make the Kessler Run either. Should I still use muratic acid or PB Blaster on studs, or with the Dormans cut their way back on? Thanks and good to see a friendly name reply!
I used PB blaster on the threads, ran the new nuts on and off a couple times.

Also used a steel brush to clean off all threads and around the studs.

Then I slobbered plenty of copper anti seize on each stud and in the nuts, then installed the gasket, sensor, and new flanged nuts. Do not overtighten because you'll either strip or break the stud.
 
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It's all good and fixed properly. Appreciate all the feedback and support. I actually used Remington Bore Brite barrel cleaner before chasing studs and it seemed to work great. Again, thank to all! DLPDLP
 

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