jm.,,I can't spin a hydro unit,,I made this to deal with only closed center systems,steer valves,SCV's,power brakes and Pumps,,I have a jack shaft with a 4020 pump mounted on one end that can be disconnected, I bored that shaft and plug welded the splinned end of a pump shaft into it,, a diverter valve that will send charge oil and pressure oil to and from ether end of the shaft,,on the end opposite of the mounted pump I have a fixture to mount a pump to test,,at that point I disconect the permanent pump..shift the diverter valve to the pump to test and let it supply the test stand for that flow/pressure test,,I spin the jack shaft with a 30HP motor and have it belted to spin the jack shaft at 2100 RPM,to simulate a tractor running full throttle,, I have a charge pump mounted to the end of the motor. When not testing a pump i shift the permanent pump back onto the jack shaft and shift the diverter valve to send charge oil back to it,,then that pump supplys the test bench to test other components by plugging into the manifold on the bench,,a pressure port on the left end,,2 ports to a steer motor ,,then 2 ports to a 8X2 cylinder, then 2 ports to 2 gauges to test a brake valve, the the last one on the right end is return oil..I mounted an oil cooler of an old combine Hydro static,,there is no fan on it but I could add one if needed,,so far I have not needed to run a fan