I know this seems like a dumb question, but I looked all through my W126 (engine 116) engine manual and there isn't a word on how to change one of these. I have 4 new ones that I hope are the right ones (BERU ZLE121, marked '1 K ohms'), and 1 of these is definitely fried on the 4th cylinder right bank rear. They are rubber-cased with a metal jacket, and feel like there's all sorts of stuff inside.
I read a post that said all you need to do is insert the wire and turn the boot clockwise, presumably to screw it in/on. Peering into the hole, though, I see a metal sleeve about the diameter of the wire, and a strange looking cylindrical cup-like piece about 1/8" diameter, that looks like it would touch the end of the wire when the wire is pushed all the way in. Nothing that looks like a screw though.
Can anyone tell me the procedure to replace one of these? How does the old wire come out? Does it need to be 'dressed' before inserting in the new boot?

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1986 560SL
2002 Toyota Camry
1993 Lexus