Downstream O2 sensor removal

[paulsome]

Has anyone out there successfully replaced their Ion downstream O2 sensor between the cat and the resonator?

I have the check engine light on, says it's the heating coil in the sensor. I ordered a new sensor, and even picked up a sensor removal tool (the socket with the hole in it for the sensor cable). The thing is, the end of the sensor where the wire is attached it butted right up against the underside of the exhaust hump, effectively making it impossible to put anything other than a wrench on this thing.

I sprayed it with some WD-40 and let it sit for a few hours, and I cannot get this thing to budge in the slightest. I don't want to strip out the sensor hex head. Does anyone know a better way to tackle this? Not exactly sure what GM was thinking when they designed this...

[Dsaturn]

This is a great wrench for the job but a little costly. http://www.autozone.com/loan-a-tools...ket/947305_0_0
Here is a cheaper wrench.
http://www.autozone.com/loan-a-tools...ket/390898_0_0
I just did mine on My L 200 and just used the box end of a 7/8 combo wrench. Since you are replacing it just cut the wires on the old one and slip the Box end on the O2 sensor then you have to use another box end on the open end of the wrench you have on the O2 sensor for leverage or tap with a hammer. Or a pipe that fits over wrench will work .
WD 40 is not a penetrating oil that is good for loosening stuck bolts. Get some PB blaster then soak it well for a few hours then try it. A warm exhaust system helps to, Not real hot but warm after running engine for about 2 minutes.
When you reinstall the new O2 sensor if you use a wrench like I did just tighten it well with the open end of the wrench.

[paulsome]

OK yeah, the one I picked up looks like your second link. I was able to eventually get that on the sensor by flexing the whole exhaust line away from the side of the exhaust tunnel that the sensor was jammed up against. It won't budge with my breaker bar. Even tried using my floor jack to put extra leverage on it.

But I'll try some PB blaster, sounds like that's the better approach. I'll let it run for a few minutes too, and see if that does the trick

[Dsaturn]

Are you sure you are turning it the right way. Remember lefty loosey righty tighty. You may have to get a mapp gas torch and heat the Bung up that is welded to the pipe.
When you say you even tried using your floor jack against the breaker bar which way was the bar facing, Toward the front or rear of the car? While facing toward the front you would have to pull down not push up.

[paulsome]

Originally Posted by Dsaturn

Are you sure you are turning it the right way. Remember lefty loosey righty tighty. You may have to get a mapp gas torch and heat the Bung up that is welded to the pipe.
When you say you even tried using your floor jack against the breaker bar which way was the bar facing, Toward the front or rear of the car? While facing toward the front you would have to pull down not push up.

I actually tried both eventually, thinking that maybe by tightening it a touch it would break loose enough to loosen it with ease. It didn't really work either way due to awkward angles, and I didn't want something else in the exhaust line with a weaker bond letting go first haha. So far I let the PB blaster set for half an hour and tried, still nothing. I gave it another dose, am letting it sit and this time will try letting the car idle a few minutes before giving it another go. If that doesn't work, then I'll try direct heat with a torch

[Dsaturn]

Being that You are in rusty upstate Ny Heat will be your best bet.

[paulsome]

Welp, what was left of the flange between the resonator and the cat pipe fully separated...so yeah I have that to deal with now. Not to mention that sensor still didn't move a millimeter. Rusty upstate NY wins this round I guess.

[Dsaturn]

That sucks, Sorry to here that. Check Rockauto for replacement pipe.

[paulsome]

After some inspection, it looks like the flanges on the resonator and cat pipe are still pretty much intact - just the bolts rusted away. So I think I can get away with grinding off and drilling out the old bolts that are stuck on the resonator and putting a new gasket in. If not, the resonator is 45 bucks on rockauto, so not too bad. But the catalytic converter is 200+ so I'd like to salvage it if I can.

The problem is that sensor is still sealed tight in there. Assuming I can get it off and the bung threads are shot, is it possible to put a new bung on the pipe? Or more likely if I can't get it out, can I just cut that section of the cat pipe off and clamp on a new one that has a fresh bung? I'm not even sure if something like that exists though haha. Rockauto only sells replacement catalytic converters as a whole unit.

[Dsaturn]

You could drill a hole in the pipe then find a thin nut that is the same thread as the O2 sensor then weld it in place over the hole you drilled. I did that on a Subaru and it worked fine. If the bung rips off you will most likely have to replace that pipe.
Heat that bung up until its red hot then try to remove the O2 sensor. I have had to do that on a lot of cars when I lived in North East PA because of the rust.

[biggman100]

Originally Posted by Dsaturn

You could drill a hole in the pipe then find a thin nut that is the same thread as the O2 sensor then weld it in place over the hole you drilled. I did that on a Subaru and it worked fine. If the bung rips off you will most likely have to replace that pipe.
Heat that bung up until its red hot then try to remove the O2 sensor. I have had to do that on a lot of cars when I lived in North East PA because of the rust.

You can buy replacement weld on bungs for anywhere from $15 to $25, and even get pipes with a bung already welded on for about the same price from autozone and advance (i do a lot of Subaru work in upstate N.Y., so im very familiar with subaru O2 replacements here). As for getting O2 sensors out in upstate N.Y., if they have been in there during any winter season, Mapp gas usually wont work. I usually take them to monro, and have them heat it up and get it loose, then replace it myself, since they wont install customer parts anymore.

[biggman100]

Both of those tools can be rented from Autozone, so you dont actually have to buy them, but, for most typical cars in upstate N.Y., there is no point. Once the O2 sensor gets rusted in there, it doesnt come back out easy.