300E- Changing Oxygen Sensor
 

I want to change the oxygen sensor as it's been in there at least 60k miles. To avoid damaging the threads in the exhaust system or rounding off the hex on the sensor, should I remove it when the pipe is cold or warm? Can I use an ordinary open-end or box-end wrench? I have some Permatex Anti-Seize #133A. Is this appropriate to use on the new one?

Thanks,

Gary

I just did mine a few months ago. It was uneventful. I hit it with some PB Blaster and while it soaked, I unhooked the wires so I could get a box-end wrench on it and it came right out. I just screwed the new one in and did not use any sort of sealant or anti-sieze.

FWIW

I'm having a very difficult time getting the oxygen sensor to budge on my 1988 300ce. Could someone please confirm that I am correct in trying to loosen it in a counterclockwise (CCW) direction. Thanks.

yes it is a standard right hand thread I would use some anti seize on the threads, undo the wires and put a box end on it if you need and some type of penatrent, if you can't budge it and another wrench as a cheater were gloves and brace yourself so you get a good pull without slipping

Thanks.

Try tapping on the end of the wrench when properly secured to the O2 sensor. Often this seems to work for me.

Haasman

I did one on a euro 280SL that was a real bear. On the advice of a long-time tech, I sprayed with PB Blaster and let it sit overnight. Then I heated the pipe with a propane torch.

I braced myself so I could use my foot and leg against the wrench. It moved about 1/4 turn at a time, and I had to re-heat the pipe 3-4 times to keep it moving.

The trouble is that if you are working on the floor, it is impossible to use a handle long enough for the leverage you need.

Applying LOTS of heat is the answer.
I normally use an Oxygen sensor socket to remove them.
It is a 1/2" drive , 7/8", six-point socket.
When used in conjunction with a powerbar, it gets those stubborn sensors out.
I also run an 18 mm thread-chaser into the pipe, before installing a LIGHTLY coated ( Anti-seeze ) sensor.;)