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| Illustration 1 | g01134080 |
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Schematic for the hydraulic system (1) Main control valve (2) Line relief valve for rod end of tilt cylinder (3) Line relief valve for head end of tilt cylinder (4) Pressure tap for rod end of tilt cylinder (5) Tilt cylinder (6) Lift cylinders (7) Ride control accumulator (8) Ride control diverter valve (9) Pressure tap for head end of tilt cylinder (10) Lift circuit relief valve (11) Ride control relief valve (12) Implement and steering solenoid valve (13) Ride control solenoid valve (14) Main relief valve (15) Parking brake solenoid valve (16) Parking brake oil pressure switch (17) Pressure tap for the parking brake circuit (18) Lift arm positioner valve (19) Float sequence valve (20) Check valve (21) Selector and pressure control valve (22) Line to parking brakes (23) Line from steering circuit (24) Pilot control valve (25) Brake accumulator charging valve (26) Breaker relief valve (27) Check valve (28) Portable hydraulic pump quick connect coupler (29) Line to brake accumulator (30) Pilot and braking pump (31) Steering pump (32) Implement pump (33) Hydraulic filters (34) Hydraulic tank (35) Pilot relief valve (36) Pilot system pressure tap (37) Pilot oil filter (38) Check valve (39) Portable hydraulic pump quick connect coupler | |
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| Illustration 2 | g01133655 |
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(1) Main control valve
(2) Line relief valve for rod end of tilt cylinder (3) Line relief valve for head end of tilt cylinder (5) Tilt cylinder (6) Lift cylinder (7) Ride control accumulator (8) Ride control diverter valve (10) Lift circuit relief valve (11) Ride control relief valve (12) Implement and steering solenoid valve (13) Ride control solenoid valve (14) Main relief valve (15) Parking brake solenoid valves (18) Lift arm positioner valve (19) Float sequence valve (21) Selector and pressure control valve (24) Pilot control valve (25) Brake accumulator charging valve (26) Breaker relief valve (27) Check valve (30) Pilot and braking pump (31) Steering pump (32) Implement pump (33) Hydraulic filters (34) Hydraulic tank (35) Pilot relief valve (37) Pilot oil filter (38) Check valve | |
The implement hydraulic system has two systems: the pilot system and the main system. The main (implement) oil system is an open center system controlled by the pilot oil system.
The main components of the pilot system are: hydraulic tank (34), pilot and braking pump (30), check valve (38), brake accumulator charging valve (25), pilot oil filter (37), pilot relief valve (35), check valve (27), selector and pressure control valve (21), check valve (20), implement and steering solenoid valve (12), pilot control valve (24), lift arm positioner valve (18) and float sequence valve (19).
The components of the main implement system are: hydraulic tank (34), hydraulic filters (33), implement pump (32), main control valve (1), tilt cylinder (5) and lift cylinders (6).
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| Illustration 3 | g01134059 |
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(33) Hydraulic filters (under cover)
(34) Hydraulic tank (40) Hydraulic tank filler cap | |
Hydraulic filters (33) are located in hydraulic tank (34). If the oil restriction through the hydraulic filters is too high (filter elements too dirty), a filter bypass valve in the tank will open and allow oil to bypass the hydraulic filters and return to the hydraulic tank. Remove hydraulic tank filler cap (40) to add hydraulic oil to the hydraulic tank.
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| Illustration 4 | g01134060 |
| (32) Implement pump | |
The main implement system has a single section gear type pump. The implement pump (32) uses the hydraulic tank as a common reservoir.
Implement pump (32) is mounted on the torque converter updrive housing and is driven by a gear inside the torque converter housing.
Implement pump (32) supplies oil for the operation of the lift and tilt cylinders.
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| Illustration 5 | g01138895 |
The main control valve is mounted in the front frame.
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| Illustration 6 | g01134064 |
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(1) Main control valve
(2) Line relief valve for rod end of tilt cylinder (3) Line relief valve for head end of tilt cylinder (14) Main relief valve | |
Main control valve (1) directs the oil from implement pump (32) to the lift and tilt cylinders.
Included in the main control valve housing are main relief valve (14), line relief valve for rod end of tilt cylinder (2) and line relief valve for head end of tilt cylinder (3).
Line relief valves (2) and (3) protect the tilt cylinders from external shocks. When the pressure in the tilt cylinder exceeds the setting of either line relief valve, the line relief valve opens to vent the excess pressure to hydraulic tank (34).
When the pressure from implement pump (32) exceeds the setting of main relief valve (14), the relief valve opens to vent the excess pressure to hydraulic tank (34).
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| Illustration 7 | g01134066 |
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(30) Pilot and braking pump
(31) Steering pump | |
The pilot system has a two section gear type pump. The two pump sections are: pilot and braking pump (30) and steering pump (31). The pumps use the hydraulic tank as a common reservoir.
Pilot and braking pump (30) supplies oil for the parking brake, service brake, and the pilot oil for the steering and implement systems.
Steering pump (31) supplies oil for the operation of the steering system to turn the machine.
Reference: For more information on the steering system, refer to Systems Operation, Testing and Adjusting, Steering System.
Reference: For more information on the braking system, refer to Systems Operation, Testing and Adjusting, Braking System.
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| Illustration 8 | g01134068 |
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(25) Brake accumulator charging valve
(38) Check valve | |
Oil for the parking brake, service brake and pilot systems is drawn from hydraulic tank (34) to pilot and braking pump (30). The oil then flows through check valve (38) to brake accumulator charging valve (25).
Brake accumulator charging valve (25) has two functions. Brake accumulator charging valve (25) maintains the pressure in the brake accumulator at a constant range while the engine is running. Also brake accumulator charging valve (25) divides pump flow between the brake accumulator system and the pilot system.
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| Illustration 9 | g01134069 |
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(35) Pilot relief valve
(37) Pilot oil filter | |
Oil flows from brake accumulator charging valve (25), through pilot oil filter (37) to pilot relief valve (35). Pilot relief valve (35) maintains the pilot system at a constant pressure, pilot relief valve (35) relieves excessive pilot system pressure through a line to the hydraulic tank (34).
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| Illustration 10 | g01138907 |
| (27) Check valve | |
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| Illustration 11 | g01134072 |
| (21) Selector and pressure control valve | |
The pilot oil flows through check valve (27) to selector and pressure control valve (21).
While the brake and pilot pump is supplying oil to the pilot oil system, selector and pressure control valve (21) will block the flow of alternate oil into the pilot oil system.
If the brake and pilot pump fails, or oil is not available, then selector and pressure control valve (21) will allow alternate oil to flow into the pilot oil system from the steering system and the main hydraulic system.
When the engine is off, selector and pressure control valve (21) provides pilot oil to pilot control valve (24) via implement and steering solenoid valve (12) to lower the bucket. High pressure oil from the head end of lift cylinders (6) enters the pilot system through selector and pressure control valve (21). The selector and pressure control valve (21) reduces the oil pressure and lets lower pressure oil flow to pilot control valve (24) via implement and steering solenoid valve (12). When pilot control valve (24) is moved to the LOWER position, pilot oil flows to the lift spool in main control valve (1). The lift spool moves to the LOWER position allowing the bucket to be lowered.
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| Illustration 12 | g01138908 |
| (12) Implement and steering solenoid valve | |
Oil from check valve (27) also flows to implement and steering solenoid valve (12).
When the implement and steering solenoid valve (12) is energized, pilot oil flows through implement and steering solenoid valve (12) to pilot control valve (24).
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| Illustration 13 | g01134075 |
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(24) Pilot control valve (under cover)
(41) Joystick control lever | |
Joystick control lever (41) controls the movement of pilot control valve (24). The pilot oil is blocked at pilot control valve (24) when joystick control lever (41) is in the HOLD position. Moving joystick control lever (41) will send pilot oil through pilot control valve (24) to main control valve (1) to move the tilt spool or the lift spool.
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| Illustration 14 | g01138909 |
The lift arm positioner valve and the float sequence valve are located in the right side of the front frame.
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| Illustration 15 | g01134076 |
| (18) Lift arm positioner valve | |
Lift arm positioner valve (18) controls the movement of the lift arms during lowering. When the lift arm positioner valve is activated, the lift arms will lower to a preset height above the ground.
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| Illustration 16 | g01134078 |
| (19) Float sequence valve | |
When the joystick control lever is moved past the LOWER position to the FLOAT position, the spool in float sequence valve (19) moves. This causes a makeup valve in main control valve (1) to open and allow oil from the rod end of lift cylinders (6) to return to hydraulic tank (34). Both the rod end and the head end of lift cylinders (6) are open to hydraulic tank (34). Lift cylinders (6) can move freely and the bucket can follow the contour of the ground.