Pre cat O2 replacement tips

[andrewwynn]

Replaced my way way way overdue O2 sensors a couple days ago and have a couple tips to help out others needing to do the same.

I tried to muscle out with a breaker bar but the crow foot slipped over the nut and started to round off the nut so I switched to impact.



The back sensor required the use of the wobble extension or flex adapter.



I used the crow foot for removal but of course had to start and stop a couple times. Once broken free I switched to the straight socket and hand tools



Here's the straight socket with impact grade flex adapter.



I was able to fold up nearly the entire cord into the socket for install: I had to carefully guide the connector around the heat shield once per revolution but it was so much easier than dealing with the twisting cord.


This is the sensor socket kit I bought for dealing with O2 sensors also has the size for some temp sensors etc.

Has two different styles of crow foot one that works great with a hammer when you have room.


Digital torque wrench one of my favorite tools. 50 N·m is the correct torque.



I bought a 5/8 thread chaser to clean the threads before installing the new sensors and it conveniently fits inside one of the sockets from the sensor socket kit


My adapter bag: 1/4 3/8 1/2 impact flex and the two shorter wobble adapters. Also the chrome parts convert a wrench into a low profile ratchet.


Like I mentioned waaaaay overdue.





Oops don't like me forget to plug in the new sensor!



Hot dog! Success. Instant improved mpg! I never get over 23 highway just got 25 on a 5 mile test drive at 60mph.

I'll know tonight if it was a fluke; making a 70 mile drive tonight.

[titodj]

Thanks for sharing...
I'm wondering, would it be easier to remove the sensor if the engine is warm?

[andrewwynn]

I think that 95% of the difficulty is the rust and when heated the sensor heats up as well as the header so both expand so probably not much help. When using a blowtorch to heat a part for removal you can heat the outer part to make it bigger.

With a closed socket you should be able to remove crusted in sensors it took maybe 150 N·m to remove post cat sensors I couldn't get impact in there but the slotted sockets tend to stretch open enough to slip so I cut off the cord so I could use a solid impact deep well socket.

If I didn't have impact I would do the same for the pre cat sensors: cut off the cord and use a solid socket (22mm 7/8"). One is slightly tighter if you have to hammer it on all the better.

Also: I add some more anti seize. I have a special kind with copper. Short term I can tell you it really really works I had to swap a sensor that was warranty replacement after maybe six months and it turned out with no difficulty whatsoever.

[richardb]

Originally Posted by andrewwynn

I think that 95% of the difficulty is the rust and when heated the sensor heats up as well as the header so both expand so probably not much help. When using a blowtorch to heat a part for removal you can heat the outer part to make it bigger.

With a closed socket you should be able to remove crusted in sensors it took maybe 150 N·m to remove post cat sensors I couldn't get impact in there but the slotted sockets tend to stretch open enough to slip so I cut off the cord so I could use a solid impact deep well socket.

If I didn't have impact I would do the same for the pre cat sensors: cut off the cord and use a solid socket (22mm 7/8"). One is slightly tighter if you have to hammer it on all the better.

Also: I add some more anti seize. I have a special kind with copper. Short term I can tell you it really really works I had to swap a sensor that was warranty replacement after maybe six months and it turned out with no difficulty whatsoever.

Kudos for all the slick DIY's you've posted lately with great images. I need to pick up one of those electric impact guns, I don't like usingmy big air gun and compressor in my neighborhood unless really necessary.

Would you say that removing the O2 sensors once the engine is hot is a good alternative to using a torch in that area for rusted on sensors?

[crystalworks]

Originally Posted by richardb

Kudos for all the slick DIY's you've posted lately with great images. I need to pick up one of those electric impact guns.

Same, on both counts. Nice job Andrew. This is one of those RARE jobs that the v8's actually have an easier time. Our pre-cats are easily accessible from underneath, harness and all.

BTW, I haven't had anymore o2 codes after swapping in that rear o2 from the parts car. Must have actually been a DOA replacement I received.

[andrewwynn]

Originally Posted by richardb

Kudos for all the slick DIY's you've posted lately with great images. I need to pick up one of those electric impact guns, I don't like usingmy big air gun and compressor in my neighborhood unless really necessary.



Would you say that removing the O2 sensors once the engine is hot is a good alternative to using a torch in that area for rusted on sensors?

Thanks for the feedback

I doubt much improvement with hot engine. My truck was 16-17 years old when I swapped O2 and the post cat wrestled out without much difficulty and the pre cat knocked out with the small impact (less than 220 ft·lb).

Milwaukeee just came out with a stubby version of their impact based on their M12 battery that has 250 ft·lb which is more than the compact M18 but is almost an inch and a half shorter front to back at less than 5".

They also came out with a mid torque 600 ft·lb model that is much smaller than the 750-1100 ft·lb beast.