Cat 922B Hydraulic problems Need HELP!

My service manual for 59A1 up says to fill the overhauled pump with oil before installing it and that rpm should be at least 600 to seat the vanes against the outer housing until the pump primes up. It also says that if it doesn't prime up within a few seconds, damage to the pump is likely.

I would take off the incoming line from the tank (it comes in from the side while the one out to the filter comes out the top toward the front) and fill the pump with oil, reinstall the line and perhaps pressurize the tank a bit and check for air leaks at the joints on the line from tank to pump. Might not be a bad idea to check the line by blowing back down it or otherwise making sure it's not obstructed. Either an obstruction or an air leak will cause problems, but you might also be in need of a pump cartridge.

I have had a gear pump go out on skid loader seemingly overnight. I'm sure it was worn before, but when it lost it's prime and the hired help started it up in the am and kept running the loader trying various things to get it to work, it was toast before they quit. New pump fixed it right up.

Could there be water in the hydraulic system ? I have seen this happen where a machine sat in a very cold winter for long period of time . The water settles to low points of the suction line , then freezes and no hydraulics until the oil was warmed with a torch.