Does anyone know what this might entail and have some advise/tips or even a how-to for removing and reinstalling? I keep getting the O2 sensor light and found that a they have a tendancy to get real dirty real quick in my area and this would save me a 100 mile trip to the dealer, assuming I could clean it out myself. Also I like to have a plan before I dismantle any part of the car, I'm not terribly fond of the keep removing this until it comes out philosophy.

 

I have been working on cars for a while and have never had to clean one, but there's a first time for everything. The O2 sensors are fairly easy to get to on the MINI. Find some pics on here of the stock header or even an aftermarket one to see where they are located. You could even just look down the back of the engine and see the "top" one. The "bottom" one is right after the cat. Disconnect the battery then unplug which ever one you are going to clean first. There is probably enough room to get a box end wrench on the sensor if you don't have a O2 sensor socket. You could use any carb/choke cleaner to clean them as long as the can says oxygen sensor safe.
Here's a pic from the OBX header thread, you can see the O2 sensor bungs...

 

I've found them pretty easily when the car is on jacks, I was more worried for how fragile they may be and if I need to do anything special with reinstall. Do you have a photo of just the O2 sensor by any chance? It looks like I'll probably end up doing my own DIY with this one.

 

I found this one on Google, don't know what it fits, but it gives you an idea.

They are not as fragile as the name implies, they have to live in a exhaust pipe. Just don't kink the harness, and re-route it exactly the way the factory did and put some never seize on the threads before screwing it back in.

 

Thanks, I think I'll be having a look at this tonight, not really sure what would need to be cleaned there though, guess I'll find out...

 

The tip of the sensor should be black when you pull it out, from carbon build up. You can try wiping most of it off, just try not to get the carbon in the little slots.

 

Thanks for the tip I'm going to go get the jack stands out now...

 

Well I've decided its under warranty, its real tight under there (I don't have room enogh to turn an open ended wrench which is why I'll wait), I can wait until my next oil service (1-2 months away) to have it more throughly checked out. Thanks for the help I'll be sure to get as many details as possible from the tech who inspects it.