Eliot, if you plan to go to the trouble of removing the upper timing chain cover to replace the rubber seal between the upper and lower timing chain covers be sure to buy the proper sealant from your local MB dealer. It's fairly expensive, but does the job. The Parts Department tech explained to me that the Service Shop techs use that sealant for many "problem" leaks regularly. It comes in a unique tube that works like a caulking gun.

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Fred Hoelzle