Post Cat Ogygen sensor - a warning to anyone attempting this job

[Mike6]

For some months lights would come on the dash and scanner indicated heater elements on bank 2 sensor. Reset the code and lights would stay off for a few weeks. My car is the 2005, 2.5SE.
Decided to replace both sensors but they seem to be in short supply, Bosch that is. You can get other makes or those generic ones where you cut the cable and reconnect at the top end of the engine but stayed clear of these. In the end, managed to get them from AutoDoc but they took a few weeks to arrive.
Jacked the car up but simply didnt have enough space to get under there and access the sensors so booked the car into my friendly local garage.
They did the job but said it was a nightmare getting the old ones out. They eventually had to resort to unorthodox methods but stripped the threads of the old sensors and retaped the thread in the exhaust. They thought that originally special grease had not been applied to the thread and basically the sensors over time welded themselves into the exhaust.
They charged £216 for fitting them which I thought was not bad for nearly 3 hours of work. I spoke to the mechanic who did the job and he said
it was an entertaining job which came close to destroying the downpipe but he was happy I wouldnt have a problem.
So beware if this is a job you are contemplating yourself.

 

[TOMGREEN413]

I won't be......

 

[colb]

Just been through this on my 2.5 see here https://z4-forum.com/forum/viewtopic.php?t=142161&start=15
Exhaust studs are awful to deal with and the exhaust sensors just as bad if seized in.

 

[yg54sg]

I have just been through this pain , 3 came out fine with a bit of head on the aftercat bank 2 of a blow lamp but the aftercat on bank 1 the threads from the sensor partially stayed in the pipe, had to use a tap and die kit to remake the thread, its now nearly perfect but slightly off centre but no leaks. I found that the Bosch sensors were available but the part numbers for one of the after cat sensors was not available so just used the same for both , I think it just means the cable is slightly longer. Mine had been in for 150k. I won't look forward to that again in 10 years time! :rofl:

 

[colb]

My exhaust down pipe bolts saga and the seized in Post Cat sensor see earlier post link for full story.
By far the the best soloution for getting the exhaust studs out is to slot the flange at the splined end of the flange to release the tension on the splined end of the studs, bottom two easy to do with a thin grinder disc but access to the top two a bit of a fiddle using a reciprocating hacksaw, once the slots are made air hammer on the studs pushes them out. As to the seized Lambda sensor only successful way of getting it out after usual cut out sensor sockets just rounded the sensor hex and just slipped around was the investment of a set of Extractor Sockets which required the top of the sensor being cut off so the socket would fit over the rounded off Hex, achieved this using a sharp chisel in the air hammer, hacksaw made little impression on the sensor. Once cut down and the socket put on with the aid of a breaker bar it broke free and unscrewed out. Had been thinking I may have had to take the Cat out to work on the sensor extraction, the extractor socket saved the day. Ran a thread chaser down the hole and then refitted the new sensor, it came with a very small amount of anti seize on the thread but I added some copperslip grease to the threads as well. Used a good fitting 7/8 open end spanner on the new one to tighten in. All buttoned up and checked the performance of the sensors using live data on my Launch diagnostics, all was well thank goodness.