1985 GSL-SE oxygen sensor replacement.
 

Bought a replacement O2 sensor, NTK (NGK) 24006 exact fit sensor, and my mechanic says the threads are wrong. He says the sensor needs to be 18mm x 1.25 and all he can find is 18mm x 1.5 pitch. Says I'm stuck because Mazda no longer sells the part.

This can't be true. Can someone please confirm? Thanks in advance for any help.

Have you tried your local Mazda dealership?

If what you have is all that is offered, then why not have him cut off the old O2 sensor bung and weld a new bung on to accommodate the replacement O2 sensor...?

That doesn't sound right. I am almost positive it is 18mmx1.5. I have bought Bosch O2 sensors and haven't had any issues.

Thanks for the answers. He, not I, checked with Mazda. They no longer sell the part and somehow I doubt they really looked it up either.

As to cutting off, he says the part is cast so that might not go well. I don't know what's going on but will get eyes on it this weekend and try to resolve. I have to believe if there was a problem this community would have a known fix.

The part that you have should fit fine. Rockauto lists it as a direct replacement. As I said, I have used Bosch and others and never had an issue with the threads. Either he is mistaken on it not fitting or somehow your O2 sensor isn't the right one (different model put in the box, but not likely). I may even have an old O2 sensor that I could show you in order to compare to what you have.

Solved
 

Got my hands on the parts yesterday afternoon. The old O2 Sensor measures 1.5 as the new one measures 1.5. The mechanic was able to run an 18 x 1.25 tap through the manifold and could not start the 18 x 1.5 so he deemed the hole 18x1.25. This was incorrect, he didn't actually measure the parts with a thread gauge and I did.

Solution was to buy an $8.00 O2 Sensor chaser at Pep Boys which is a tap with the first 1/4 inch or so with no threads. This helps align the tap and worked well. I only chased for 2 turns and removed the tool. New sensor would then start and tighten.

Thanks for the help. The final answer: 18mm x 1.5 mm pitch is the correct dimension.

Good deal. Glad to see that you got it figured out. :nod: