Cat 320 B Hydraulic issues

I'm having some issues with my 320B excavator and here are the symptoms:

Little or no response on all hydraulic functions.

Lots of flow through the suction line from the tank to the pumps.

Little or no engine lugging or power loss when hydraulics are used.



This problem started to gradually get worse in about a half hour period before not working at all. Changed all filters and strainers with no results. help. please.



Thanks

Cat 320 B Hydraulic issues