W221 Hydraulic Trunk Opening/Closing Complete System Upgrade $320 if you send in your parts first. Ships back filled with hydraulic fluid.

Hydraulic cylinder upgrade: Top Hydraulics replaces the original seals with a far superior material. The cylinder is part of pump assembly p/n 2218001548 aka A 221 800 15 48. Do not cut the lines - they unbolt at the pump. There is a surcharge of $50/ea. for damaged lines. In the rare event that the polished cylinder shaft has rust on it, Top Hydraulics can replace the shaft with a polished and hardened stainless steel shaft for an additional $100.

Pump upgrade: The upgrade service includes overhaul of the pump, noise reduction in the pump to a level lower than a new pump, and replacement of the electric motor if necessary. This will make the pump better than a new one.