some functions stopped working, like rear wheel steering, stinger wouldn't retract all the way, boom wouldn't lower all the way. Changed 2 hydraulic filters. they are seated properly. Added universal hydraulic fluid. Problem persists, boom comes down slowly and choppy. Rear wheels don't move, Stabilizer arms work ok, winch goes up and down. Fluid in tank is clear but after running is kind of foamy. Manual is no help! Does system need bleeding? if so how? Any one familiar with these machines? It's a 1972. Very frustrated. Thanks
If you ran it out of oil, you can damage the pump, or maybe only a section of the pump. Typically cranes will have multiple sectors on the pumps, so that there's a different section that runs the winch, than the section that runs the boom. You may have only lost the boom/ steering section. Alternatively, you may have a issue in the swivel, and have oil bypassing that sector within the swivel. Pushing that oil to tank. The fact that the winch is fine, leads me to believe you only have issues in the section that does the boom. Maybe just pull a line off or loose on one of the non working functions and see if its even moving oil. This should just be a old vane style pump, so it shouldn't have much problems priming itself. Time to loosen some lines and maybe put some pressure gauges on.
I'll try loosening some lines, thanks for the advice.