with this test.
-Disconnect the rod end of the suspect cylinder.
-Use tractor hydraulics to extend it fully.
-Disconnect hydraulic hose for the rod end of the cylinder, at the loader end
-Put the end of that hose in a clean bucket, and secure it.
-Start the tractor and extend that cylinder again. DO NOT RETRACT!!!!!
-If a stream of fluid comes out of the hose, the piston needs to be re-packed.
-If it only drips, your problem is elsewhere.
-Shut off the tractor and reconnect the hose and cylinder if okay, or finish removing the cylinder for repair if required.
-Once removed, place the cylinder end in the oil bucket and push down on the rod end to collapse it and purge the oil from the cylinder. Now there is a minimum of oil to contend with when the cylinder is disassembled, either by you or the repair shop.
A glycerine filled 5,000 psi pressure guage costs about $20. That plus the appropriate 'T' fitting will eliminate doing this kind of test and can be used anywhere on the system to locate specific problems.