Trying to remove my downstream O2 sensor (Cali). Should be simple enough. Part due today so I PB Blaster'd the @#$%@# out of it yesterday and again this afternoon. It doesn't look that bad. I read that it should take a 12mm wrench to remove the nuts that hold it on. I dropped a 12mm socket on it and it felt like it was tight but with almost no pressure at all, it just gives. Nuts didn't look rounded off but my socket isn't grabbing it well enough and neither is my ratcheting wrench or open ended wrench. Tried some US wrenches, tried getting an 11mm socket on it, nothing else fits. Because of all the other crap in the way, I can't get anything else on it such that it would turn even if I could get it to grab (i.e. clench wrench, vice grips, pliers, adjustable wrench - tried them all).

I guess I'm going to have to pay someone to remove the old sensor so the new one can be installed. Unless someone has a good suggestion?

I'm in the same boat with mine and I keep forgetting to look at it again. Best bet I think would be small needle nose vice grips. But, go buy new nuts from the dealer before you mangle these.

I replaced both O2 sensors on my '97, recently. The nuts holding the sensors on were so corroded that a wrench would not work.

I soaked them with PB Blaster for a few days, and then heated them up with a propane torch for about 30 seconds, clamped a pair of needle nose vise grips on, and they all came loose with just a bit of force.

wow, i guess i got really lucky with mine... i replaced mine a couple months ago without any trouble what so ever. took less than 30 minutes to remove and replace both of them.

First let me say that is probably the one thing I truly love about CA.

In addition to the other advice, make sure you guys are using a 12mm 6 point socket. Seems simple enough, but you would be amazed how many people don't think about that simple stuff.

I just cut an 02 out of an old MR2 exhaust I had. Those wouldn't come off at all, Had to weld a new flange with new studs on the thing.

Guess I was lucky too, replaced mine 2 months ago with zero problems at all.
Standard old box wrench and it came loose very easy, almost no rust on it at all.

Bolt out kit from Sears works well. It will destroy the nut, but should work assuming it can get on it and the stud isn't to much higher than the nut. Basically it's a hardened socket with a spiral cut to it. The harder you torque it the more it digs into the nut.

I dont give a rats you know what about the nuts at this point. They can be replaced. And the corrosion on them wasnt bad at all. I bathed them in pbb for ever 24 hours anyway just in case. But the problem is not that they wont turn. I cant even get enough grip on them with anything to begin with to even know if they will turn. I went looking a 6 point wrench and nobody in town has one in a 12mm. My neighbor works at the advance auto store and thinks he may have something to help me with between there and his toolbox. Will try again tomorrow.

Had the same problem man... Just replaced mine & the DS O2 was all corroded.. Had to beat the heat shield up to open up some room.. Took a hammer and beat a 11mm 12pnt box end wrench onto it.. It's amazin' what a little rusty nut will make you wanna do after 30 mins.!!

My rear nuts only came off in pieces. I used a small pair of Vise-Grips (5") that got on there perfectly and really clamped them down. I also worked it with an 11mm and maybe a 10mm socket hammered on there and then used the little Vise-Grips on that. Eventually it came off. The good news is the studs are way harder than the nuts and came through it all intact.

EDIT: I really recommend the mini-Vise-Grips". Very useful tool. Here they are:

http://www.nationaltoolwarehouse.com...mm-P55579.aspx

Not sure what you have for clearance but try putting some heat to it. Concentrate on heating and expanding the surrounding area....again, if there's enough room.

FWIW; most of the exhaust stuff I've worked on required heat before anything came loose.

Durk, I've got vice grips like that. There is no angle that I can find to get them clamped onto the nut and still have room to turn it. Some needle nosed ones might be worth a try. But I'll have to buy/borrow some of those.

I'll get it out. It's just frustrating how these types of easy tasks always seem to turn out to be not so easy for me. Fedex didn't show up with my new sensor until 9:35PM last night anyway. So much for "on time, all the time".

Yeah, they were on my street last night at the same time. 'Tis the season....

T4R-Finally, thanks for this thread actually. I just finally remembered today to go pick up new nuts for mine so I can swap my sensor out this weekend.

No problem PitBull. I was just able to get mine done. Don't underestimate the 6 point socket/wrench. I tried a standard 12mm socket yesterday, a standard 12mm open ended wrench, and a 12mm ratcheting closed end wrench and couldn't even get enough of a grip on the nuts to move them. I borrowed a 12mm 6 point from my neighbor this afternoon and it hooked right up and I got the nuts off easily. It grabbed the nuts so well, I had to poke the nuts out of the socket afterwards. I had to pry the gasket off and then used some PB blaster and cleaned around the opening real good. Smeared some anti-sieze around the bolts and put the new gasket and sensor on. Went to the hardware store for some new nuts. Of course they didn't have any direct matches in stainless. So I picked up 2 stainless 13mm nuts and 2 stainless lockwashers that fit and tightened the sensor down.

Cranked the truck and let it run for a few minutes and it's still running smooth and hasn't thrown a code yet. I plugged in my code scanner and everything looks good so far. Worse case, I have to put new CAT(s) on it, but I'll have a new O2 sensor regardless.