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| Illustration 1 | g02279875 |
Components of the Secondary Steering Valve (1) Outlet to the steering control valve (2) Primary steering check valve (3) Secondary steering check valve (4) Inlet from primary steering pump (5) Inlet from secondary steering pump (6) Resolved pump oil pressure sensor 1 (7) Resolved pump oil pressure sensor 2 | |
The secondary steering valve is located on the upper left inside frame. The secondary steering valve is also located above the secondary steering pump.
The secondary valve contains two check valves. The check valves act as a selector valve. Check valve (2) monitors the primary steering oil pressure. Check valve (3) monitors the secondary steering oil pressure.
During normal operating conditions, oil pressure from the primary steering pump keeps check valve (2) unseated. At the same time, secondary steering check valve (3) is seated.
This operation allows pressure oil to flow from the primary steering pump, through the secondary steering valve, to the steering control valve through outlet (1). With secondary steering check valve (3) against the seat, no pressure oil flows to the secondary steering pump.
If the primary steering pump fails, the flow of pressure oil from the primary steering pump stops. After a brief pause, the electric motor that is attached to the secondary steering pump starts. This action causes the secondary steering pump to pump oil.
The oil from the secondary steering pump flows to the secondary steering valve. The pressure oil causes secondary steering check valve (3) to unseat. With no oil pressure from the primary steering pump, the pressure oil from the secondary steering pump causes primary steering check valve (2) to seat.
The oil then flows to the steering control valve through outlet (1). With primary steering check valve (2) against the seat, no oil is allowed to flow to the primary steering pump.
Note: When a loss of primary steering pressure occurs, the Caterpillar Message Display indicates a Warning Category 3 alarm.
Note: When the secondary steering pump activates, a Warning Category 3 occurs. This action causes the secondary steering alert indicator and the master action light to flash. This action also causes the action alarm to sound.
ReferenceFor additional information on the pump pressure sensors, refer to Systems Operation, "Secondary Steering System (Electrical)".
ReferenceFor additional information on the Caterpillar Message Display, refer to Service Manual, UENR0359, "Medium Wheel Loader Series K Monitoring System".