hs_300e, the MB dealers sell a black sealant that works well when redoing the upper timing chain cover U-shaped seal. Talk to the Parts Department at your local MB dealer about the proper sealant for that application.

I have read where some folks recommend Hylomar for the upper timing chain cover seal replacement so it may be a matter of which is most convenient/inexpensive for you to procure.

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Fred Hoelzle