Changed the seat bar solenoid but still locks up. Could it be air in the Hydraulic system? How about the brake solenoid? How do I check each thing and rectify the problem. Funny thing is when it gets really warm it works fine but it is awful hard to get it up to a good operating temperature when it is minus 30 here. Celcius that is. Also to note sometimes it locks up so hard it stalls the machine and once in a while the oil temperature light comes on but not always.