Interesting no one responded to this post, I did this repair yesterday, but reused the old components, as I didn't have access to any new parts on a sunday.

I cleaned the area, cap and seal sterile with chlorinated brake cleaner, and used an MB branded hi temp silicon. I coated the seal, pushed it into its recess in the cover and beaded around the cover edge, then installed and torqued to cover back on. all surfaces were oil free. It work perfect! I've ordered the new pieces and will install when they arrive, but i'm dry for now. . .

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Mark
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THE WHITE FLEET
2016 GLE300d 4-MATIC 38K BROWN!
2012 S350 Bluetec==94k WHITE

2007 ML320 CDI==166K WHITE (FOR SALE)

Under new management:
2005 E320 CDI--140K--WHITE
1995 E300-Diesel-133.5K--THE CAR IS BLUE
1986 300SL--97.5K (European) AND WHITE. Back in Europe!
1991 190E 2.3-73K California Perfect.--WHITE
1995 E320-Wagon-159K--WHITE (recently scrapped)
1987 300D Turbo-213K--WHITE
1987 190D 2.5 Turbo-288K--WHITE