it may be air in the hyd. system. I had to take the low pressure line loose from the pump to remove the starter i was having trouble with. after i got it back together i bled the system by loosening the high pressure line. i got air bubbles and after a while the hook up raised, but after a while i have to bleed it again and i still get air bubbles. i have dome this several times, but same results. i took it back apart and replaced the o ring on the low pressure fitting and the hose that connects the two tubes that comes from the sump to the pump. same results. this tractor is powered by a 3 cyl. perkins diesel. the hyd. pump run off the cam shaft gear.