Blockage in Supply or Output Lines to Main Hydraulic Pump.
Thermal shock is an extremely rare condition caused when hydraulic system is
operated for some time without turning steering wheel. Fluid in reservoir and system
is hot and steering control unit is relatively cool (more than 50°F [10°C] temperature
differential). When steering wheel is turned quickly, the result is temporary seizure
and possible damage to internal parts of steering control unit. The temporary
seizure may be followed by total free wheeling. Failure to follow this caution may
result in damage to equipment.
Air in Hydraulic System.
Repair leak in pump suction circuit.
Leaking Fitting on Steering Circuit.