Cabriolet owners repeatedly flag the powered top as the big aging expense: multiple hydraulic cylinders with seals that dry-rot and leak, plus the fabric separating at the seam above the rear window. Costs cited run into the thousands, though some faults are trivial (electric relays) and the top's tensioning straps can be a cheap DIY fix.
Convertible top hydraulics and seam separation
Mercedes-Benz CLK55/CLK63 AMG (C209) · mechanical