I have a 2008 s63 with 91k getting a loud whining noise when I turn the steering wheel in either direction don't see any leaks and fluid level is full also getting a message "park assist currently unavailable see oper. Manual " any help would be great

Have you had it "scanned" by a garage? I use my service garage (not Mercedes benz) as they are cheap. They have a scanning tool which will pull up all faults. This will identify the issue as reported by the Benz Computer. Hope this helps a little.

It could be the steering pump or serpentine belt. These cars are still hydraulic steering not electric.

First thing is check your power steering fluid level.

Second is replace the poly-V / serpentine / auxillary drive belt.

Third change the power steering pump.

Nick