I need to replace my O2 sensor (MY03 STi) and there are two types of tool available for removal/replacement. One is like a modified large spark plug socket with the side removed. The other is a sort of crows-foot spanner with square drive socket. Which one fits best? The sensor comes so close to the body that even if you could fit the socket you could not get a rachet into it. The sensor is recessed some way into the heat sheild so the crows-foot option may not reach the flats of the sensor. Anyone had experience with this?

Are people still replacing the 4-wire Zirconia types with universal fits or are there direct replacements at substaintially less than the >£300 price Subaru want for these?

 

Not replaced one but I dont think you will have enough room to get a crows foot in the best option is the socket type with the cut out for the wiring. They are not expensive anyway only about £5.

 

I've done it a few times with a plain old combi spanner............

 

You couldn't get a combination spanner on mine. For a start you can't get it over the wiring and secondly the flats on the sensor are right down inside the heat shield.

 

just done mine with a 22mm open ended spanner. Mine is an early classic though with the sensor in the headers.

You can get angled open ended spanners from the halfords professional range that may do the trick

 

easiest way is to remove the heat shields first which is a real pain. And then a 22mm combi spanner can be used. It is possible with a socket and extension from under the wheel arch with the liner removed(pulled back), but still a pain. The first time i did this the sensor was so tight that the socket rounded on it so i was forced to remove the shields.

 

Thanks guys. I can well believe this job will a tough one.

 

I get in spots like this all the time at work, not with car engines but similarly tight, mecahnicaly speaking . Too many skinned knuckles and swearwords now just steer me toward making the part I want to get to accessible. If you need to drain and remove other parts that are easy to work on, then do it.... it doesn't take long.

Not as long as a tear on your hand to heal, or for a new part to arrive