Fred is correct about the timing chain cover for an inspection of all the rails. Only a glimpse of the corner one upper through the oil fill, removing valve covers gets a better look at both uppers. Uppers take more chain slap, so when they're brittle and break it takes out the lowers--along with valves,leave shards in the oil pan, etc. Not much point in rolling in a new chain without changing at least the upper rails.

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Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)