Case 4490 Hydraulic Issues

We picked up a used 4490 with around 3.5k hours?for some tillage jobs using a 20ft disc.? The first issue we had was with the alternator going?out causing crab steering issues which made us park it.? This spring we put a new alternator in it and fixed the crab steer issues.? Then the hydraulic issues started.? When lifting the disc while the hyd.?oil was colder it seemed to lift ok but a little slow.? As the oil warmed up the lifting got slower and slower each pass until it wouldn't lift at all (Case Hy-Tran Hyd Oil).? A neighbor recommended to test how much pressure we got coming out of the SCV's using a liquid filled pressure gauge and to change out the hydraulic filters.? I changed filters and?tested each and they ranged from 850-900lbs when the tractor was warm, slightly higher when cold.? I've been told it should be around 1200??

How would you recommend a guy trouble shoot an issue like this moving forwards?? I know very little about hydraulics.? I wanted to isolate the issue to lower the labor fees of getting it tested at a shop.? Could be the hydraulic pump going bad, or a hydraulic bypass issue but is there ways of testing that myself?

I'll add some pics I snapped.

Any advice for a new Case?guy?

link for the pics: https://imgur.com/a/WoSGi

A common complaint when a hyd pump is getting weak is that they lift better when the oil is cold and gets worse as the oil warms. Simply because the oil gets thinner as it warms. To be sure the pump is the problem it would be best to bring the tractor to a qualified service shop with the proper testing equipment that can do a complete testing procedure. That pump is rather expensive, I would hate to purchase one if it is not necessary, Rod.