HEAD 2690388 - Caterpillar

Illustration 1 g00386693
Location of the Steering Pilot Valve (1) STIC. (2) Steering pilot valve.
Illustration 2 g00367214
Pilot Valve (Steering) (3) Handle (4) Link (5) Link (6) Plunger (7) Plunger (8) Spring (9) Spring (10) Cap (11) Cap (12) Spring seat (13) Spring seat (14) Spring (15) Spring (16) Return port to the hydraulic tank (17) Spring (18) Spring (19) Passage (20) Passage (21) Spool (22) Spool (23) Port to the left neutralizer valve (24) Inlet port from the selector and pressure control valve (25) Port to the right neutralizer valveWhile the engine is running, pilot oil flows from the selector and pressure control valve to the steering pilot valve. Pilot oil enters the steering pilot valve through port (24) .STIC (1) is attached to handle (3). When the STIC is not being moved, springs (8) and (9) keep handle (3) in the CENTERED position. Pilot oil flows through inlet (24) to metering spools (21) and (22). In this position, the spools block the flow of pilot oil to the steering control valve. This causes the pilot oil to flow back to the hydraulic tank for the steering and brake systems.When the STIC is moved to the LEFT TURN position, handle (3) also moves to the left. This causes link (4) to move plunger (6) downward. As the plunger moves downward, the plunger overcomes the force of spring (8). This causes the spring to compress. As the plunger moves downward through cap (10), the plunger also causes the following components to move downward: spring seat (12), spring (14), spring (17) and spool (21) .When spool (21) moves downward, passage (19) opens. Pilot oil can now flow from inlet port (24) into passage (19). The pilot oil then flows through passage (19) and past spool (21). The pilot oil then flows out of port (23). The pilot oil flows from port (23) to the left neutralizer valve. Next, the pilot