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| Illustration 1 | g06232027 |
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854K Wheel Dozer. (1) Steering control valve (2) Oil cooler (3) Check valve (cooler bypass) (4) Relief valve (steering pilot) (5) Oil filter (steering pilot) (6) Fluid sampling port (7) Gear pump (steering pilot) (8) Hydraulic tank (9) Check valve (primary pilot supply) (10) Check valve (secondary pilot supply) (11) Pilot valve (STIC steering) (12) Neutralizer valve (A) Steering pressure tap (right steer) (B) Steering pressure tap (left steer) (C) Pressure tap (steering pump) (D) Pressure tap (steering pilot supply) (H) Pressure tap (steering pump signal) | |
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| Illustration 2 | g06232040 |
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(7) Gear pump (steering pilot)
(9) Steering pump | |
The pilot oil can be supplied by one of three sources:
- Steering pilot gear pump (7)
- Steering pump
- Secondary steering system (if equipped)
Steering pilot gear pump (7) is the main source of pilot oil. The pump is a gear pump that is located on the steering pump.
Pilot oil may also be supplied from the steering pump. The main steering pump supplies pilot oil if the pilot oil pump fails. Refer to Systems Operation, "Steering High Pressure System" for more information.
The secondary steering system (if equipped) can also provide pilot oil. The secondary steering system is activated if the pump drive fails or if the engine fails. Refer to Systems Operation, "Secondary Steering System" for more information.
During normal operation, gear pump (7) withdraws oil from hydraulic tank (8). Pressure tap (D) is available on the diagnostic plate for testing pilot oil pressure. The pilot oil then travels through filter (5). Machines are equipped with a filter bypass switch that is attached to filter (5). The warning switch will alert the operator when the filter is clogged. When the filter is clogged oil bypasses the filter.
From the steering pilot oil filter (5), the pilot oil can travel through one of two routes. One route is through pilot oil relief valve (4). The other route for pilot oil is through the pilot valve (STIC steering).
Relief valve (4) limits the pilot oil pressure of the pilot oil system. Relief valve (4) is set to
The pilot oil can also travel through primary pilot supply check valve (9) to stic pilot valve (11). The secondary pilot supply check valve (10) prevents pilot oil from flowing away from the pilot valve.
As the operator moves the pilot valve (STIC steering), pilot oil travels through neutralizer valves (12) to the steering control valve. Pilot oil acts upon steering control valve (1) that is located in the steering control valve housing. This action allows high-pressure steering oil to travel to the steering cylinders. When the neutralizer valve comes in contact with the frame, the neutralizer valve shifts. The pilot oil that is acting on the spool valve is directed back to the hydraulic tank. Steering control valve (1) is then allowed to shift back to the NEUTRAL position.