Help with hydraulic issue

[Lt220]

I recently purchased 2007 JD 4320 hydro. Everything works on it but i'm having severe issues with air in the fluid. I have checked for leaks on suction side and no problems have been found. When I crank the tractor the sound of the hydraulic oil rushing through the lines from the pump is all you can hear. The power steering squeals really bad. I've replaced the power steering valve hoping that would fix the issue but it didn't. My question is could the pump be going bad and causing the issue? It definitely seems to be starving for fluid. The fluid and filter are both new.

 

[beenthere]

Do you have any known hydraulic pressures at any of the hyd. ports? Any other symptoms to cause the ps valve to indicate replacement?

 

[wdchyd]

Do you have a screen in the the reservoir? Maybe clogged, or a bad pump shaft seal sucking air.

 

[Lt220]

Im going to drain all the fluid tomorrow and check the sump screen to make sure it's clean. Im not sure if it's sucking air at the sump line or not. It doesn't appear to be. I'll know more tomorrow when I check the screen.