I just changed the spark plugs on my 1995 E420 -- it turned out to be easier than I was worried it might be (after reading some horror stories here). The 17mm open-end wrench was a necessary tool and made taking off the spark plug connectors relatively easy.

Unfortunately, when removing the last one, I broke the head off the orange bakelite connector:



(A new one for comparison: )




I was able to remove it from the plug and re-install it and it functions fine but obviously I want to replace it as soon as possible. My question is how do I connect the existing wire to the new connector pictured above? Does it screw on or does the metal part need to be opened? Thanks!

The wire screws out of the boot. At the tip of the wire, where it goes down into the boot, there's a metal cap with a threaded stem (visualize the valve stem cover on your tire with a small threaded stem sticking out towards you).

You can usually get the old wire unscrewed without the metal tip at the end of the wire coming off. You have to twist the wire counter clockwise. Maybe some WD-40 or Kyroil would help here.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles