CAT 304C FPK Hydraulic issue

[hoistthesails]

Hi!

Newbee here. Just bought a 2007 CAT 304Cr TFPK02409 3600hrs
Lovely little machine.
Everything works fine except one thing.
The valve block and thick hose from the left side of the valves to the pump makes a ratling sound when the lockout handle is down. The auto idle also stay in high revs when leaving the controls. Nothing is moving when I leave the controls.
It seems to be worse when the valve block is leaning down slope.
Lockout handle up, and it idles down and stop ratling.
I dont have a manual. Changed the filter installed form the top of the tank. (suction filter?)
I have another two steel meash filters from the filter supplier. But not sure where it goes.
I dont know if the oil is correct. Or how long since its been serviced.

Any ideas?

Pardon my bad english. I'm Norwegian

 

[hoistthesails]

*This is solved.
Opened and checked all solenoids. All fine
Changed oil and filters.
Traced and checked harness. All good.
Tried to open the thumb switch for auxiliary, but it's glued shut.
Drenched it in electric cleaner, and now its fine - for now.
Can't buy the switch, only the whole handle, and its expensive.