I'm going to be replacing the O2 sensor by cutting off the old nut which by now looks like a blob of rust. So I'm looking to buy stainless steel nuts as replacement beforehand. Anybody know the diameter and pitch of the studs that hold O2 sensors in place on a stock exhaust?

 

I am not positive,but I wanna say 6mmx1.00...

I would not cut them if you do not have to,If you cut them and are not carefull you will have to replace the stud.

If you can,remove the nuts,remove the sensor,gasket,then take a die and go down the studs to clean the threads,then install with new nuts.


http://www.amazon.com/Hanson-9727-He...7199238&sr=8-1

I know this is going to sound crazy...But the best thing to get rusted nuts off,if they will come off w/o heat.....is a pair of really small ignition pliers,like these,they will crush the nut before the pliers slip,really..:

http://buy1.snapon.com/catalog/item....0&group_ID=749

or

http://www.tools-plus.com/channellock-424.html

or

http://www.sears.com/shc/s/p_10153_1...0070921x00003a

 

I'd guess that's about right, but getting the right nut before getting dirty would be nice.

The little of the stud that does stick out past the nut looks to be zinc plated, and pretty much looks like new. There is unknown under the nut, probably a lot of oxidation, but not rust. From looking at it the nut might crumble with any pressure, or might not.

Toyota just sucks when it comes to rust protection.

 

best thing is to get new nuts at dealer

12mm


the studs are likely fine. toyota sucks at rust but on these studs on 3rd
gen pipes the studs do not rot. you just need to carefully chisel
off the old melted/rusted nut, and wire brush the threads

then chisel off the fossilized toyota gasket on the bung. it may
look 100% smooth but stock gaskets do that. they can form
into a smooth impossible to remove chunk and that needs to be
chipped off to bare metal

 

12mm is probably the wrench to use when the nut it new After all the rust was off I had a 10mm wrench spinning on it. But it all came apart fairly easy with some heat.

For future generations that hopefully will use search: the studs are a metric 6mm diameter and 1.25 pitch.

 

Stainless steel FTW!

Turns out the stud is some sort of bronze/brass alloy, hence the lack of rust.

 

Are you sure it's 6mm? I (one of those future generations who used search) found this thread and was frustrated when the local Ace didn't carry a 6mm 1.25 die for thread chasing. It seems that 6mm 1.25 is an unusual combination. Turns out that on my 1992 Pickup, the stud is 8mm 1.25 pitch. The original unstripped nut required a 12mm wrench. The replacement stainless nuts needed a 13mm wrench. I'm adding this in case it helps anyone else who find this information from a search.

 

Yep 8mm x 1.25 is correct. Here's part of a writeup I did in the 3.4 swap section in case anyone else needs to repair or make a whole new O2 sensor bung.

I couldn't find anyone that sells a Toyota O2 sensor bung to weld into the new exhaust piping. After talking to a friend that works at the local Toyota dealer about where to get one, he says why don't you just make one? I hadn't thought of that Jason, thanks for the idea. So here's how to make your own O2 sensor bung.
I started with a piece of 3/8 steel and marked the outline with a gasket and drilled and tapped some holes (8mm x 1.25):



I used some exhaust studs from the dealer that were left over when I was putting on the ORS cross-over.


Then I started cutting it out with a cutoff wheel on an angle grinder:

After using a grinder and beltsander to smooth it out:


Now that was one bung, but I need two for the 5VZ. The first one took me about 2-3 hours to make so I decided to try cutting an old one out of my old 3.0 exhaust pipe and using it. That took about 2-3 hours too, counting replacing the old studs and smoothing it out with a grinder and beltsander too.

Here's the two side by side, the one I made from scratch will have to be welded in parallel to the pipe since it's not curved to the shape of the pipe:



BTW the factory nuts are steel locknuts, better than using lock washers. Do NOT use nylock nuts, the nylon will just melt LOL.



Oh and put lots of anti-seize on those nuts and threads so you won't have that rust problem again.

 

5+ years later the stainless steel nuts look good! Take a lesson Toyota!

 

My rear O2 sensor popped out (the nuts rusted away completely) and the studs were steel(!!!) 8mm x 1.25.

 

I have a shield in front of my o2 sensor that i had to rip off to get the bolts off.

Did you guys put a new shield on? Do you think it's necessary? Toyota says the shield is discontinued. Any other models that have a shield I could use if it's necessary?

Also, where did you go to get the stainless steel nuts? I used to know of the store that had really high quality stainless steel bolts and nuts but forgot the name? Thanks! - FASTENAL, dunno how i forgot!

 

My local feed store has them here. So would Lowes, Home Depot, etc. Shield isn't necessary. Find another one at pick n pull.

 

Seeing how hard it was to get the shield off, i definitely would not want to go through the trouble of taking one off another vehicle at a yard! haha

I'm going to swing by a nearby Fastenal and grab the 2 m8x1.25's

 

Now THAT'S funny! Sorry but switching to Toyota after 20 years of GM, I had to laugh. There's just no comparison, and I'll never go back.
This old thread saved me a lot of frustration, I appreciate it!!
...oh, and I'll take my Toyota's rust over ANY GM, any time.