With such ow hours and use, I would suspect air in the system. Have you used it for any extended period of time? My 463(older version of S70) makes some weird noises if it has been parked for several months, but clears up after a couple hours of heavy use.
If you have not changed the hydro filter, do that first. Cut the old out apart and check for metal debri. small amounts are normal.
Check ALL hose connections for tightness. Loose fittings can cause an air leak and cavitation, causing noise.
