I think that 95% of the difficulty is the rust and when heated the sensor heats up as well as the header so both expand so probably not much help. When using a blowtorch to heat a part for removal you can heat the outer part to make it bigger.

With a closed socket you should be able to remove crusted in sensors it took maybe 150 N·m to remove post cat sensors I couldn't get impact in there but the slotted sockets tend to stretch open enough to slip so I cut off the cord so I could use a solid impact deep well socket.

If I didn't have impact I would do the same for the pre cat sensors: cut off the cord and use a solid socket (22mm 7/8"). One is slightly tighter if you have to hammer it on all the better.

Also: I add some more anti seize. I have a special kind with copper. Short term I can tell you it really really works I had to swap a sensor that was warranty replacement after maybe six months and it turned out with no difficulty whatsoever.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)