The pneumatic (PSE) system running the soft-close doors, trunk, central locking and the pop-out trunk handle is a common age failure, with door pumps still available but the trunk pump now NLA and the membrane going brittle. Fixes range from resetting a fuse or refurbishing/converting to manual mode, to replacing the vacuum pump. …
PSE vacuum soft-close doors, trunk and pop-out handle
Mercedes-Benz S-Class (W140) · mechanical