VALVE GP-PILOT 2013359 - Caterpillar

View Under Steering Control Unit Console
(2) Steering control unit (SCU). (8) Instrumental panel.Hydraulic oil tank (6) provides oil for the steering, propulsion and vibratory systems. The hydraulic oil tank is located behind the operators platform on the left side of the machine.
Rear Of Platform
(6) Hydraulic oil tank.
View of Pivot Joint
(4) Steering cylinder.When the steering wheel is turned, two double acting steering cylinders (4) receive oil from steering control unit (2) so that the machine can make the desired turn. With the SCU in the spring centered position, oil is blocked to the steering cylinders. Whether the steering cylinders are activated or not, oil goes through the SCU to the brake manifold.
Under Platform/Right Side
(5) Hydraulic Oil Filter. (8) Low Charge Pressure Sensor.If hydraulic oil filter (5) becomes plugged, a pressure drop is created across the hydraulic oil filter. When the pressure decreases 350 kPa (50 psi), the filter bypass valve opens and oil flows through the filter bypass valve to the spring loaded check valve. When the pressure reaches 1220 kPa (175 psi) in the passage between the bypass and check valve, the spring loaded check valve opens and the oil flows to the hydraulic oil cooler The spring loaded check valve prevents the brake pressure from decreasing below 1220 kPa (175 psi).Low charge pressure sensor (8) is located in the input line into hydraulic oil filter (5). When charge pressure drops below 1100 kpa (160 psi) an audible alarm sounds and a light on the steering control console illuminates.Steering Pump
Steering Pump
(1) Priority valve spool. (2) Pressure compensator valve. (3) Steering pump gears.Pump Operation
The steering pump is a gear-type pump mounted to the accessory drive on the engine. The pump turns clockwise when the engine is running. The steering pump supplies oil to the steering system and charge oil to the propulsion and vibratory systems. Inside the pump is priority valve spool (1) which is a pressure compensated flow divider. Priority valve spool (1) divides flow between the steering circuit and the charge circuit. The steering circuit has priority. Pressure compensator valve (2) maintains a constant five gpm of oil flow to the steering system. Return flow from the steering circuit goes to the charge circuit.Output oil from steering pump gears (3) act against the lower end of priority valve spool (1). Oil goes through the orifice in the priority valve spool to supply pressure on the end of the spool. Oil pressure forces priority valve spool (1) up to allow oil flow to the charge system.The orifice serves as a flushing passage for the oil that puts pressure on the bottom of the priority valve spool. The orifice minimizes priority valve spool (1) from bottoming against each stop during changes in the steering load. During operation, priority valve spool (1) oscillates.When pressure compensator valve (2) opens, it allows oil flow to the steering system. This keeps a constant flow in the steering system.Operation (No Turn)
The oil from the steering pump priority valve goes through inlet check valve of