I went to the junkyard a couple of weeks ago and picked up a new crossover pipe to replace the pipe I bought there the last time that's FUBARed out of shape, causing the cat to hang too low (making lifting the car with anything other than an alignment rack a pain as the side of the car had to be lifted to get the arm underneath) and the intermediate pipe to be WAY out of alignment, hitting the front passenger's seat belt receiver bolt and the front heat shield in the rear wheel area. The pipe was complete, and appears unbent as it aligns nearly perfectly (just a tad close to the engine oil pan but it isn't throwing the entire system out of line), it was not cut to remove the cat from the rest of the system on the donor (same 91 I pulled the engine harness and ECM from that was badly wrecked in the front, has the marks on it where the cat had been installed), and even had an O2S in it. I removed the O2S to put in my existing sensor that is less than a year old, and this is where the problem lies.

The O2S I pulled out of the pipe was an exact match to my current sensor, but I wasn't taking the chance of installing a bad one and, like I said, my current one is less than a year old. I had a bit of a problem starting the removal, not having my 7/8" socket available and being forced to use a flare wrench and not having the pipe installed on a car, but it came out nice. The problem is in that my newer sensor won't go in the hole all of the way, leaving about 1 full thread out of the hole and not compressing the gasket, and probably causing an exhaust leak (SOOO sick and tired of that blasted leak... I finally got the donuts sealed and now there is yet another exhaust leak!).

Does anyone on here know the thread size of the O2S so I can get a tap to clean up the hole? No, I can't pull the sensor and then drive to a parts/hardware store as I need my car to get there and it's rather difficult to pull a 500+ degree sensor in a parking lot.

 

I thought that they were metric. Can you use the one that came with the pipe for the short term till you find out what size the threads are. I have a new one for my car, but cant get the old one out. It's stuck real bad.

 

They ARE metric, but that doesn't tell me the thread size so I can get a tap...

As part of removing an O2S, I always cut the pigtail off (actually, the last one I replaced I accidentally ripped the pigtail out of during a harness swap) so I can get a real socket on it (7/8" deep well socket as opposed to the more expensive sensor socket or crow foot I don't have), and I didn't have access to the deep socket for this, so I just used my 7/8" flare wrench, meaning I also had to knock off the outer shell of the sensor. All of which means the old one that was in the pipe is useless.

When I had to remove the O2S I accidentally pulled the pigtail out of, it was stuck in there really good. I got it out with a breaker bar and my floor jack, using the floor jack to push on the bar. Even my impact wrenches weren't working on that sucker. You may also need to use a torch to heat the bung.

 

i dont recall the exact size but if u goto any parts store and pick up a sparkplug thread chaser it is the right size, they are usualy black and look like a dbl ended tap with a nut in the middle

goodluck

 

As usual, I got more info here than I did from the guys on 60*V6...

I'll try to get there tomorrow. Once I get this out of the way, maybe I can start on some body work...

 

I was thinking about getting the bung good and hot and try it. I can try take my new sensor to a shop that a friend of mine works at and see if we can figure out what size tap you would need, if you can wait that long. I probably won't know till tomorrow night. You have already helped me out, and I have seen so many of your posts helping other people out, it's the least I can do to try help you out!

 

M18-1.5 is the thread.

As '89 posted same as a 18mm spark plug, which makes the spark plug chaser the hot ticket.

Best to heat the bung good and hot before removing one that has been there for a while. Then chase the threads before installing a new one or even the same one.

RBob.

 

Thanks guys. I went and got the thread chaser this morning and managed to rethread the bung before it started to rain. It took forever and a day to get the threads cleaned, but I don't think I've ever had an O2S go into the bung as easily as it did after I chased the threads. I actually got it in all the way down to the gasket before I had to use a wrench.

:hail: :hail:

 

That's great. I need to go get one, so if it ever stops raining here I can try get mine out and put in a new one.