2020 hydraulic question

[BillFinn]

The main hydraulic pump pressure adjustment needle and seat are leaking. This makes the pump surge. We are going to order a new needle side from Amazon. Not available anymore from Deere. Any other tricks out there I could try while I wait. How about lapping it? Any good ideas on how I would do that while it's in the tractor?

 

[Tx Jim]

What type of diagnostic procedures did you use to determine stroke control valve was faulty? Has hyd oil suction screen been checked/cleaned lately & hyd filter relief valve checked to be sure it's seating as designed ? Did you ever attempt utilizing a destroking screw while engine was operating? Have you checked to be sure front pump is receiving sufficient supply from trans pump? I can't remember ever seeing/hearing of many stroke control valves requiring replacement when I was employed at a JD dealership for 21 yrs

 

[BillFinn]

Yes filter screen was replaced, we installed a rebuilt pump and now have a surge. About 1000psi swing if it's set at 2300psi if I turn pump down to 1000lbs runs smooth. Charge psi is at 65lbs don't have flow neter but running into a bucket charge flow seems pretty good. I presently have high psi line capped off with a gage so eliminating everything on tractor minus charge pump circuit. The rebuilder asked me to try a destroying bolt, which did quite pump while destroyed but did not fix our problem. Now he wants us to replace the pressure adjuster tapered spool. He thinks this is not seating correctly and causing this condition. Thankyou for your interest!

 

[Tx Jim]

IIRC trans pump pressure should be 155-165 psi & flow should be 5 GPM.

 

[BillFinn]

Rebuilder assured me we should be fine. But obviously a flow test on the charge pump will be next on the menu. Just a thought if the pump is dead headed not flowing oil wouldn't 65 lbs charge the inlet

 

[Tx Jim]

I think 65 psi isn't enough. With hyd filter cover removed clean container under filter opening rotate engine crankshaft with starter for 15 seconds & measure amount of oil in the container. There should be a little over 1 gallon of hyd oil in container.

 

[Harry in Ky]

Just personal opinion here, but I think you're placing too much faith in your "rebuilder" and he's blowing smoke at you. I don't have near the experience Jim has but I've never seen a similar system with 65 PSI charge pressure that was working properly. Then again, I've never seen one "surge" like what you describe.

 

[BillFinn]

I am checking charge pressure with a tee into cooler line between cooler top and reserve tank. Ideally I should be before main pump.