Hi all,

I am replacing my O2 sensors. The one before the cat came out no problem. The one after the cat came out about 1.5 turns and then stops. I can screw it back in to the bung but it will only unscrew about 1.5 turns which is only about half way. Need to get it out.. Carbon deposit?

Any advice much appreciated.

David

 

Rust and or Carbon Deposits. I am assuming you are using an O2 Sensor Socket, if not get one. Past that penetrating oil that creeps and heat would be my approach, Good Luck.

 

Hi David,
Cut the wire off, slip a closed-end box wrench over the barrel hex, and hit the wrench with a mallet.
Andy ;-)

 

Hi Guys,

Thanks for your help. I go t it out, using heat and persuasion method. But the threads in the bung are now bunged up enough that the new sensor won't thread in. Attached is a shot of the old sensor, threads are pretty galled up. But I assume the SS in the exhaust system is a lot harder than the sensor thread material, so I tried threading in the other old sensor in the hope it would clean up the threads in the bung enough to allow the new sensor to engage (up stream one which came out easily) and it also would not thread in so I forced it a bit and it got galled up. Seems I need to clean up the threads in the bung. No idea how to do that without taking it to a machine shop. Which of course means another day on my back disassembling exhaust components and who know what other collateral damage.

[img]file:///C:/Users/dpenick/AppData/Local/Temp/msohtmlclip1/01/clip_image001.jpg[/img]

Reminder, this car has 49,000 miles and is in very nice condition. I doubt the sensors have been replaced nor the exhaust system has been disassembled before. I started this saga because of PO401. I understand we are just eliminating possible sources before we clean the SAI ports.

Any suggestions on how to clean up the threads in the cat bung so the new sensor can go in, much appreciated. For example, what is the thread if I need to

buy a tap?

David

 

Just clean up the threads with a tap and install a new sensor. Pretty common issue.
I'm just seeing this now, but I knew the sensor would come out looking the way it does based on your first post.

 

O2 thread chaser. Will do the trick.

 

Make sure and throw some anti-seize on there before threading on new ones. It'll make them easier to insert and a breeze to remove.

-Scott

 

Hi Scott,
Good point.
If adding some apply it sparingly and in such a way that it doesn't contaminate the sensor.
The ones in the Bosch box I seem to recall come with it applied.
Andy

 

Hi All,

I tried two different thread chasers today, could not get either one to start. I guess its on to the tap unless anyone has another suggestion. The Bosch sensors did both come with a dab of anti-seize on them, but I applied more.

David.

 

Hi All, I just wanted to report that the threads got cleaned up with a tap and the sensor is installed and test driven. All good. Thanks very much for your help. One thing that was a bit tricky, the taps I could find were all a little too long. Ended up cutting off about 1.5 inches with my Makita. Then of course no square drive left but I was able to run it in with mu trusty vice grips. With the lack of clearance and all the odd angles, working on my back, etc. I was worried about getting the tap in straight and there is no way to know if you are cutting new or cleaning up old threads, but it seems to have found the originals and the sensor took a good torque. Plenty of anti-seize for next time..