Hydraulics "jumpy" and noisy

[Wyld Bill]

Hey guys I really need your help.
Posted this quite a while ago but didn't get much help.

I have a 2004 Mahindra 2615 hydrostatic tractor.
This past summer I let a buddy of mine borrow it (first mistake I know)
While he had it the ailing bucket control valve finally failed completely.
So he marked all the hose connections, removed the hoses, spilled a bunch of hydro fluid on the ground, installed a new control valve, and added Mahindra hydraulic fluid to top it off.
I got the tractor back in late fall and noticed the hydraulics were a bit "jerky"
I didn't use the tractor much until we started getting snow. I changed all of the hydro filters.
Now I'm noticing a real problem with the tractor.
There is a lot of hesitation in the hydraulics. I mostly notice it in the FEL use but some times in the steering too.
It's like a surge, hesitation, accompanied by a noise like "dut, dutttutut" as it is "fetching up"
So could it be that he mixed Mahindra fluid with the John Deere fluid I had in there?
Did he get dirt in the system and ruined the pump?
Could the hoses be hooked up wrong some how?
Am I sucking air???

 

[J_J]

Yes, it does sound like air causing intermittent operation.

However if you have used the loader many times since then , the air should have been purged.

If you continue to have air in the system, check the pump input tube for leaks.

Also, look in the tank for air bubbles.

If your loader works in all positions, then the hoses appear to be correct.

You might do a pressure check to see to see if the pressure is intermittent, or bouncing around with the lever at max.

 

[SSdoxie]

It does sound like wither restriction in suction line or drawing air in the suction line. My old Kubota would do this when the suction screen in bottom of the transmission started getting plugged. Is there a suction screen in the tractor?
One way to test for air in suction is to apply some (not a lot) air pressure to the reservoir while operating to see of problem goes away.