HOSE 8Z7078 - Caterpillar

Illustration 1 g00853705
Secondary Steering Control Valve in the NEUTRAL Position (1) Pressure reducing valve. (2) Inlet from the steering pump. (3) Steering cylinder crossover relief valve. (4) Inlet from the secondary steering pump. (5) Outlet to the hydraulic oil tank for the steering system and for the braking system. (6) Secondary steering relief valve. (7) Diverter valve. (8) Pilot port. (9) Spool. (10) Port for the shuttle valve. (11) Springs. (12) Retainer. (13) Pilot oil port. (14) Return oil passage. (15) Port for right turns. (16) Passage of the supply oil. (17) Port for left turns. (18) Return passage. (19) Relief valve.
Illustration 2 g00853708
Typical example of the steering control valveNote: The secondary steering control valve is located on the left inner frame behind the cab.Standard steering control valves and standard secondary steering control valves consist of the same basic components. Additionally, standard steering control valves and standard secondary steering control valves have the same basic functions, unless there is a loss of primary pump flow.Reference: For additional information about the operation of primary steering control valves, refer to the Service Manual module Systems Operation, "Steering Control Valve" for the machine that is being serviced.Although the basic components of a standard steering control valve and of a standard secondary steering control valve are the same, secondary steering control valves contain the following additional components:
Inlet (4) for the secondary steering pump
Secondary steering pump relief valve (6)
Diverter valve (7) If the primary steering pump fails, diverter valve (7) sends oil from the secondary steering pump. The oil is then pumped into oil passage (16). This will continue to occur when the machine is moving forward or backward.When the operator moves the STIC steering control lever in order to make a left turn, pilot oil flows from the pilot control valve through the right neutralizer valve. The oil then flows through the neutralizer check valves and to pilot oil port (13). The pilot oil acts against retainer (12). The force of the oil overcomes springs (11). This causes spool (9) to move to the left.When spool (9) moves to the left, oil in passage (16) flows past spool (9). The oil then flows into port (17) for left turns. The oil then flows through the lines to the rod end of the left steering cylinder. The oil in port (17) then flows through the lines to the head end of the right steering cylinder.Steering oil pressure is maintained at 14000 700 kPa (2050 100 psi). The pressure is maintained by a relief valve in port (6).