PUMP GP-PISTON 3742570 - Caterpillar

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Steering System Schematics------ Pilot Oil Lines (1) Left Steering Cylinder (2) Right Steering Cylinder (3) Pilot Control Valve (4) Steering Wheel (5) Steering Control Valve (6) Crossover Relief Valve (7) Shuttle Valve (8) Check Valves (9) Spool Valve (10) Check Valves (11) Shuttle Valve (12) Backup Relief Valve (13) Steering Pump (14) Pilot Oil Pump (15) Pressure Reducing Valve (16) Hydraulic Tank (17) Screen (18) Diverter Valve Group (19) Diverter Valve (20) Secondary Steering Pump (21) Secondary Steering Relief Valve (22) Selector Valve (23) Pressure Switch (24) Secondary Steering (if equipped) (A) Pilot Valve (Oil Manifold) (B) Pilot Circuit (C) Case Drain (Implement Pump)Your machine may be equipped with command control steering. Machines that have command control steering will steer differently than other machines. The turning speed of the machine depends on the rotational position of the steering wheel. The machine will continue to articulate as the steering wheel is rotated. When the steering wheel is allowed to return to the center position, further articulation of the machine is prevented.The primary steering system has two basic circuits. These circuits are the pilot oil system and the high pressure system. The 824H Wheel Dozer is equipped with secondary steering. Secondary steering is a third circuit.Pilot Oil System
The pilot oil system controls the movement of spool valve (9). The primary source of pilot oil is pilot oil pump (14). Oil from the pilot oil pump flows to a screen. The oil then flows into pilot circuit (B). Pilot oil then flows through shuttle valve (11) and into pilot control valve (3). As the operator turns steering wheel (4), pilot oil is allowed to flow through pilot control valve (3). Pilot oil then flows through quad check valves (8). Pilot oil then flows to the end of spool valve (9). The pilot oil pressure shifts the spool valve into the desired position.Excessive pilot oil that cannot pass through spool valve (9) flows through an orifice and back to hydraulic tank (16) .Pilot oil can also be supplied by the steering pump. If pilot oil pump (14) fails, steering oil pump (13) will supply pilot oil. Steering oil pump (13) sends oil through pressure reducing valve (15). This drops the steering oil pressure to the pressure of the pilot oil system. The oil then flows through shuttle valve (11) and into pilot control valve (3) .High Pressure System
The high pressure circuit supplies the oil for steering cylinders (1) and (2). Steering oil pump (13) withdraws oil from hydraulic tank (16). Steering oil pump (13) is a load sensing piston pump. The steering pump has a variable displacement. Steering oil pump (13) supplies oil to spool valve (9). A load sensing line connects to the flow compensator valve on steering oil pump (13). Relief valve (12) maintains the maximum allowable system pressure.As steering wheel (4) is rotated, pilot oil shifts spool valve (9). High pressure oil is then allowed to flow to the steering cylinders. As high pressure oil is sent to