02 downstream studs…thread pitch?

Hi all. I’ve seen a few threads with my problem, but no info.

I’ve been having a persistent CEL 0420 for my bank 1 downstream sensor. I purchased a new Denso unit and the sheer ugliness of what I found was not what I was planning lol. The nut were rusted to the point of being dissolved. They pretty much crumbled off the studs. The sensor popped out fine, but I found that even the SS gasket was dissolved into nothing (I’m suspicious that my sensor wasn’t even bad, but the bad gasket is what threw the code. Just a hunch )

The problem is that now the stud threads are all galled up with rusty nut. I want to take my tap/die kit and chase the threads to clean them up. But I can’t tell which thread it is. The rust extends up near the tip of the stud, so I can’t get the die started without chancing damaging threads, if I happen to choose the incorrect pitch.

Best I can tell, it seems to be M8, either 1.00 or 1.25 pitch. Any help would be much appreciated.

 

You could try removing the stud and replacing it.

 

This is what I'd be tempted to do.

But knowing me stop-gap, I'd wire-wheel the stud, go into my nuts and bolts bin, find a nut that threaded on after it's cleaned up, then check the thread pitch of the nut on my nut/bolt thread gauge.

 

See my thread…here

 

M8 x 1.25 is the size for the nut.

 

I had thought about that, but I can’t get 2 nuts on the stud. Not to mention, the bung itself is also rusted badly enough that the stud base is partially showing. I fear disturbing it. At some point, I’ll need to cut the pipe and install another bung.

This is what I'm going to try, I guess. Not much room, so probably have to get out my little Dremel with the wire wheel.

Perfect! Thank you!

 

Thanks to info posted by @Jack McCarthy, the thread pitch was indeed correct. I was able to chase the threads with my tap/die kit and install the new gasket and sensor. No CEL after 10 miles. Unfortunately this fix will only be temporary, as the bung has deteriorated and I expect another leak after 1 winter. A new bung is only $12, welding free (my boy), but I dread beyond words getting the cat couplings apart from the manifold. I guess I shouldn’t complain. It’s still much easier to work on this truck opposed to my Honda Odysseys.

Now I only have to address my fluids in my rear diff, transfer case etc.

 

An inductive bolt heater or oxy-acetylene torch to get the bolts red hot should alleviate your concerns over breaking those collector manifold bolts free if you don’t think they’ll come out with an impact.

 

Thank you! Always good info from you guys on this forum