Got a ford 3910 1988 model with a steering issue. Replaced leaky power steering hydraulic cylinder, worked good for about an hour then the gearbox at the end of the steering wheel shaft started leaking. Bad gasket. Replaced gasket and tractor worked great for about 5 minutes. Then the steering wheel got hard to turn and locked up. Shut it down for a couple minutes. Cranked back up and it worked fine for about 2 minutes then locked up again. Limped it to the barn. It has been suggested that I bleed the power steering system. Any suggestions on how to do this? Thanks!