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Changing 02 Sensor

Mighty.Mighty_XJ

Mighty.Mighty_XJ

NAXJA Forum User
Location
VA ... in the dark
So I'm trying to change the downstream 02 sensor on my '99 XJ & I can't get the darn thing to turn! I'm a bit afraid I might break something, but I've given it a darn good try and no success. I do have 02 sensor sockets. Any tips about getting this rusted POS off here?
 
Put some heat on it with a torch. Heat it until is is glowing red, if necessary.
 
Soaked in PB Blaster, then I drove mine around until it was hot, and finally cut the wire so I could slip the box end of a wrench around it. Prevented slippage and, after some choice words, it came off.
 
Thanks for the suggestion. I don't have a torch, but I'll see if I can get one. Not that I know how to use it anyway.... I did spritz the nut with PB blaster. Was that a bad idea? Haven't tried it since.
 
I've had good luck heating it, then spraying it, then heating it and spraying it and repeat. The spray cools it, the heat does the obvious and have yet had this fail. It doesn't have to get all that hot, I've done it with a heat gun before, though a torch is quicker. With this method you don't have to get it red hot.

The repeated expansion and contraction weakens or breaks the bond.
 
I just let the engine warm up. If its already hot then let it cool down some so you don't burn yourself. Then they come out with a long handle 3/8" ratchet.
 
Oh, didn't know a heat gun would be sufficient. I actually have a very good one here. But isn't PB Blaster flammable? Gonna have to read the can. I won't run the engine. The cat gets much hotter than the pipe & I was already touching it with my arm.
Gonna try the heat/spray method in the morning.
 
it is flammable.
when you spray it on a hot part it just turns to smoke and helps cool the part.


the differential heating/cooling helps break the bond loose
 
Mighty.Mighty_XJ said:
Oh, didn't know a heat gun would be sufficient. I actually have a very good one here. But isn't PB Blaster flammable? Gonna have to read the can. I won't run the engine. The cat gets much hotter than the pipe & I was already touching it with my arm.
Gonna try the heat/spray method in the morning.
Click to expand...

A good one will go to 1000*!
 
I will second the Kroil suggestion.

And if you can't find that quickly enough you can make your own 50/50 blend of ATF and Acetone. That is supposed to be even better than Kroil. And yes, that too is quite flammable, so don't get it in places where you don't want a little extra excitement.

Also, once you do finally get it to break loose, don't try to just keep threading it out. My experience has been that it is best to unthread it a quarter turn, then thread it back in, then out a half turn, then back a quarter turn, then out a full turn, then back a half-turn... Basically you want to clean out the threads as you try to remove the part. Otherwise you can break something loose and then gall the threads to death and end up with yet another problem.
 
Worst case scenario, take it to an exhaust shop. They have a torch and plenty of experience changing O2 sensors. And they can cut it out and replace the bung if necessary.
 
Up here in the northeast, O2 sensors just suck to get out. Often they strip the threads out of the exhaust system on the way out too.

Whatever you do, I would run a tap (cheap ones are available on ebay for a few bucks - you want M18x1.5 thread in this case) through the threads carefully to clean them back out, and install with high temp copper antiseize if the new one does not have antiseize on the threads already. Low temp aluminum antiseize won't usually do much for O2 sensor threads.

If the socket tries to spread open, put a hose clamp around it, it doesn't do much but it gives you just a little more torque before it starts slipping.

edit: nickel antiseize like md21722 says, not copper or aluminum based.
 
Last edited:
Actually Nickel is anti-seize is what's called for, and comes pre-installed on NTK sensors. Nickel has a higher heat rating than copper. Nickel should also be used on exhaust manifold bolts/studs if you're going to use anti-seize there. Copper won't hold up.
 
md21722 said:
Actually Nickel is anti-seize is what's called for, and comes pre-installed on NTK sensors. Nickel has a higher heat rating than copper. Nickel should also be used on exhaust manifold bolts/studs if you're going to use anti-seize there. Copper won't hold up.
Click to expand...

Thanks for the correction, I'll have to remember that.
 
when changing mine, I did it after i drove the jeep so the exhaust was hot. I cut the wire and used a regular socket on a 3/8 breaker bar, attached to the breaker bar was about a 3 foot cheater pipe. I laid down on the ground and put pressure on it with my foot as much as i could and it broke free. The new NTK sensor already has antiseize on it as the poser above mentioned^^
 
For what it's worth, Nickel anti-seize looks almost like moly grease, dark gray. Copper has a distinctive copper color to it. The regular anti-seize is silver in color.
 
Like already said, spray, heat, cut the wires to use socket or wrench, once it starts moving, work it back and forth, a little at a time, there is carbon and stuff in the upper threads. Working it back and forth, loosens and removes it, making it easier... once it moves, don't force it....
 
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