Main cat O2 replacement, bumper off?

[m1tch]

Hi all,

I have tried to replace the main cat O2 sensor with a replacement, it seems that there is very very limited access to the sensor, I can't use my 22mm ring spanner due to a lip around the cat heat shield and the O2 socket I have just bought fits fine however I can't get anything in there to really apply enough leverage.

Do I need to take the bumper off to get enough access to the sensor to replace it? As I am guessing its the original its been on there for a million years so is going to need a fair amount of torque to crack it loose etc.

Any advice is helpful!

[Call the midlife!]

Going from memory can you not remove the nappy and get at it from underneath? Fairly sure the rear light has to come out to get to the plug though.


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[Carolyn]

You need a long socket.  Some members have them and know where to get them.  Mine was inherited many moons ago.  I'm sure someone will inform you where to get it.

something like this:
 m http://www.ebay.co.uk/itm/Sealey-SX022- ... SwLqFV8Uc4 m

[ptennisnet]

If it's the post cat sensor, I had to take the cat section out and get some heat on it - I only have one of those propane weed guns so it wasn't elegant but it did work.

[Fin]

Going from memory can you not remove the nappy and get at it from underneath? Fairly sure the rear light has to come out to get to the plug though.


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Replaced mine a couple of weeks ago. This is exactly how I did it.

[PhilzMR2]

No need to remove bumper or rear light. Spray with Plusgas or similar the day before and on the day you do the job. Use a long O2 sensor socket which is like a spark plug socket with a slit for the sensor cable. Use a half inch drive breaker bar or extension. Mine came out easily after Plusgas spraying. Job took under 30 mins.

[m1tch]

No need to remove bumper or rear light. Spray with Plusgas or similar the day before and on the day you do the job. Use a long O2 sensor socket which is like a spark plug socket with a slit for the sensor cable. Use a half inch drive breaker bar or extension. Mine came out easily after Plusgas spraying. Job took under 30 mins.

Thanks for that, I bought the long O2 socket especially, not really able to get a breaker bar under there so might need to jack the car up, will get some plusgas, think the sensor has been in there as OEM so its seen a few miles!

[m1tch]

Hmm that thing in on TIGHT! I have even managed to run an impact gun with a few adapters to try and get enough torque on this thing to break it lose - tempted just to buy a new cat at cats2u as I am not sure of how good the current cat is in terms of emissions - is the main cat O2 used for emissions at all? The manifold O2 sensors seem to be ok in terms of showing values.

[m1tch]

Its out! Phew, that took a while, managed to get it out by using one of those universal joint things on the socket and then about 2 extension bars at a 45 degree angle to get the assembly clear of under the car to then use a breaker bar! Found out that the sensor itself seems to be slightly bent which didn't really help and was probably the reason why the sensor had stopped giving any readings!

Anyway, good used sensor back in and the car does seem happier - not getting any popping on the overrun when blipping the throttle.

[jonbill]

I'm a bit surprised it makes a difference - I thought the post cat o2 sensor is just reporting on whether the cat is working or not but the ecu doesn't use it to vary anything.... anyone know?

[shnazzle]

Mentioned this a while ago. It does affect fueling. If it detects the cat needs more fuel to be more efficient, it will do so.
It's rare for a car to use the post-cat this way, but the 2 does