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| Illustration 1 | g01062657 |
Main Hydraulic Schematic for the Braking System (1) Front service brakes (2) Hydraulic oil temperature sensor for the front service brakes (3) Parking brake (4) Parking brake limit switch (5) Parking brake pressure switch (6) Brake pedals (7) Service brake control valve (8) Parking brake control valve (9) Accumulator for the front service brakes (10) Accumulator for the rear service brakes (11) Accumulator pressure switch for the front service brakes (12) Accumulator pressure switch for the rear service brakes (13) Check valve for the accumulator for the front service brakes (14) Manifold (15) Check valve for the accumulator for the rear service brakes (16) Oil pressure sensor for the front service brakes (VIMS) (17) Oil pressure sensor for the rear service brakes (VIMS) (18) Check valve for the brake manifold (19) Check valve for the brake pump (20) High pressure screen (21) Brake manifold (22) Hydraulic oil tank for the steering system and for the braking system (23) Breaker relief valve (24) Brake pump (25) Hydraulic oil temperature sensor for the rear service brakes (26) Rear service brakes (27) Pressure switch (VIMS) (28) Case drain filter for the braking system (A) Pressure port for the front service brakes (B) Pressure port for accumulator (10) (C) Pressure port for accumulator (9) (D) Pressure port for the front service brakes (E) Pressure port for the rear service brakes (F) Pressure port for the rear service brakes | |
Note: To determine the general location of a main brake system component, refer to the section for the appropriate component's description.
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| Illustration 2 | g01063512 |
(20) High Pressure Screen. | |
High pressure screen (20) (if equipped) is located by the transmission oil filler tube on the left side of the machine. High pressure screen (20) contains a screen that protects the hydraulic system in case of a component failure. The high pressure screen may be removed and cleaned.
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| Illustration 3 | g00646971 |
(27) Differential Pressure Switch. (28) Case Drain Filter. | |
Case drain filter (28) (if equipped) is located under the access door in the cab platform. Case drain filter (28) provides additional protection of the hydraulic system against contaminants.
If the machine is equipped with the Vital Information Management System (VIMS), differential pressure switch (27) is available. Differential pressure switch (27) is for case drain filter (28) .
Breaker relief valve (23) is part of hydraulic oil tank (22) for the steering system and for the braking system. Breaker relief valve (23) controls the amount of vacuum and the amount of pressure buildup in hydraulic oil tank (22).
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| Illustration 4 | g01063516 |
(24) Brake pump. | |
Brake pump (24) is a variable displacement piston pump. The brake pump draws oil from hydraulic oil tank (22). A pressure control valve on the pump senses the load requirements of the brake circuit. The pressure control valve then maintains the pressure by upstroking the pump or by destroking the pump.
Check valve (19) is for the brake pump. The check valve is in the pump pressure line near brake pump (24). This check valve helps to reduce pressure spikes that may be in the brake circuit.
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| Illustration 5 | g01063559 |
(14) Manifold. | |
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| Illustration 6 | g01063560 |
(9) Accumulator for the front service brakes. (10) Accumulator for the rear service brakes. (13) Check valve for the accumulator for the front service brakes. (15) Check valve for the accumulator for the rear service brakes. | |
The oil then flows through manifold (14). Manifold (14) allows the oil to flow to check valve (13) and to check valve (15). The oil then flows to accumulator (9) and to accumulator (10) .
If the pressure in one accumulator is less than the pressure oil from brake pump (24), the check valve for that accumulator will allow the pressure oil to charge the accumulator. If pressure output from brake pump (24) decreases, check valves (13) and (15) prevent pressure oil from flowing back to the brake pump from the accumulators.
The accumulators store energy for the front service brakes and for the rear service brakes. Also, the accumulators supply oil for the front service brakes and for the rear service brakes. Additionally, accumulator (10) stores energy for the parking brake circuit. Accumulator (10) also supplies oil for the parking brake circuit.
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| Illustration 7 | g01063561 |
(21) Brake manifold. | |
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| Illustration 8 | g00104382 |
Location of the Service Brake Control Valve (7) Service brake control valve. | |
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| Illustration 9 | g00104494 |
(6) Brake pedals. | |
The oil then flows to brake manifold (21). Brake manifold (21) routes the oil to service brake control valve (7). When either brake pedal (6) is depressed, the pressure oil flows through service brake control valve (7). When service brake control valve (7) actuates, pressure oil flows to front service brakes (1) and to rear service brakes (26) .
Depressing either brake pedal causes spool movement in service brake control valve (7). This allows oil from the accumulators to flow to front service brakes (1) and to rear service brakes (26) .
However, depressing the left brake pedal first limits the amount of power that is available through the drive train by limiting the amount of impeller clutch pressure. This provides more engine power for the rest of the hydraulic system. Depressing the left pedal assembly even farther actuates the service brakes at each wheel.
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| Illustration 10 | g00104383 |
(A) Pressure port for the front service brakes. | |
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| Illustration 11 | g00104384 |
(F) Pressure port for the rear service brakes. | |
There are several pressure taps on this machine. Pressure tap (A) is for the front service brakes. Pressure tap (F) is for the rear service brakes.
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| Illustration 12 | g01063574 |
(11) Accumulator pressure switch for the front service brakes. (12) Accumulator pressure switch for the rear service brakes. (18) Check valve for the brake manifold. (21) Brake manifold. (B) Pressure port for the accumulator for the rear service brakes. (C) Pressure port for the accumulator for the front service brakes. (D) Pressure port for the front service brakes. (E) Pressure port for the rear service brakes. | |
Brake manifold (21) also routes the oil to pressure taps (B) and (C). To check the pressure for the front service brakes, use pressure tap (D) on brake manifold (21). To check the pressure for the rear service brakes, use pressure tap (E) on brake manifold (21) .
Pressure switch (11) is for the accumulator for the front service brakes. Pressure switch (12) is for the accumulator for the rear service brakes. Both pressure switches are located on brake manifold (21).
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| Illustration 13 | g01063578 |
(16) Oil pressure sensor for the front service brakes. (17) Oil pressure sensor for the rear service brakes. (18) Check valve for the brake manifold. (21) Brake manifold. | |
If the machine is equipped with the Vital Information Management System (VIMS), two oil pressure sensors will be located on brake manifold (21). Oil pressure sensor (16) is for the front service brakes. Oil pressure sensor (17) is for the rear service brakes.
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| Illustration 14 | g00104454 |
(5) Parking brake pressure switch. (8) Parking brake control valve. | |
Check valve (18) is in the drain line from the parking brake line. The oil also flows into parking brake control valve (8). Accumulator (10) also provides pressure oil for parking brake control valve (8). Pressure oil also flows to parking brake pressure switch (5) .
When parking brake control valve (8) moves to the disengaged position, oil from the accumulator flows through parking brake control valve (8). The oil then flows to the parking brake. This causes parking brake (3) to disengage.
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| Illustration 15 | g01063594 |
Location of the Parking Brake (3) Parking brake. | |
Parking brake (3) engages automatically when the supply pressure from the accumulators drops below 6035 ± 515 kPa (875 ± 75 psi). This causes parking brake pressure switch (5) to open.
When the oil pressure increases to approximately 8270 kPa (1200 psi), parking brake pressure switch (5) closes. This stops the Warning Category 3 alarm if the transmission was in a forward speed position or in a reverse speed position. However, if the transmission was in neutral, the Warning Category 1 would stop.
Parking brake limit switch (4) functions as an override switch for the transmission.
Axle Oil Cooler
854G Wheel Dozer (S/N: AMP1-337) and 992G Wheel Loader (S/N: ADZ1-540)
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| Illustration 16 | g01063778 |
Hydraulic Schematic for the Axle Oil Cooler (29) Rear axle housing. (30) Rear brake manifold. (31) Axle oil cooler for the rear axle. (32) Axle oil cooler for the front axle. (33) Front brake manifold. (34) Front axle housing. (35) Axle oil cooler pump for the front axle. (36) Axle oil cooler pump for the rear axle. | |
Axle oil cooler pumps (35) and (36) circulate the oil which flows through both axle housings.
Axle oil cooler pump (35) circulates the oil through axle oil cooler (32) and front brake manifold (33) and through front axle housing (34) .
Axle oil cooler pump (36) circulates the oil through axle oil cooler (31) and rear brake manifold (30) and through rear axle housing (29) .
854G Wheel Dozer (S/N: AMP338-UP; A4W1-UP) and 992G Wheel Loader (S/N: ADZ541-UP; AZX1-UP)
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| Illustration 17 | g01066925 |
Hydraulic Schematic for the Axle Oil Cooler (37) Screen group for the front axle. (38) Screen group for the rear axle. (39) Check valve for the rear axle. (40) Rear service brakes. (41) Rear brake manifold. (42) Front brake manifold. (43) Front service brakes. (44) Axle oil cooler for the rear axle. (45) Axle oil cooler for the front axle. (46) Check valve for the front axle. (47) Axle oil cooler pump for the rear axle. (48) Axle oil cooler pump for the front axle. | |
Axle oil cooler pumps (47) and (48) circulate the oil which flows through both axle housings.
Axle oil cooler pump (47) circulates the oil through axle oil cooler (44). When the engine is started and the axle oil is cold, the oil from axle oil cooler pump (47) can not easily flow through axle oil cooler (44). The oil pressure will increase in axle oil cooler (44) and the check valve (axle oil cooler bypass) (39) will open. Check valve (39) limits the maximum oil pressure in axle oil cooler (44) to 586 ± 69 kPa (85 ± 10 psi). When the temperature of the oil increases, the pressure of the oil decreases. When the spring force is greater than the force of the oil pressure, check valve (39) will close. The axle oil flows through axle oil cooler (44). From axle oil cooler (44), oil circulates through screen group (38) and rear brake manifold (41) and through both brake housings of rear axle (40) .
Axle oil cooler pump (48) circulates the oil through axle oil cooler (45). When the engine is started and the axle oil is cold, the oil from axle oil cooler pump (48) can not easily flow through axle oil cooler (45). The oil pressure will increase in axle oil cooler (48) and the check valve (axle oil cooler bypass) (46) will open. Check valve (46) limits the maximum oil pressure in axle oil cooler (45) to 586 ± 69 kPa (85 ± 10 psi). When the temperature of the oil increases, the pressure of the oil decreases. When the spring force is greater than the force of the oil pressure, check valve (46) will close. The axle oil flows through axle oil cooler (45). From axle oil cooler (45), oil circulates through screen group (37) and front brake manifold (42) and through both brake housings of front axle (43).
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| Illustration 18 | g01063597 |
(2) Hydraulic oil temperature sensor for the front service brakes. | |
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| Illustration 19 | g01063599 |
(25) Hydraulic oil temperature sensor for the rear service brakes. | |
Hydraulic oil temperature sensor (2) for the front service brakes is located on the front axle housing. Hydraulic oil temperature sensor (25) for the rear service brakes is located on the rear axle housing.
The hydraulic oil temperature sensors activate a warning in the cab when the temperature of the oil reaches approximately 90°C (194°F). When the temperature of the oil cools to approximately 85°C (185°F), the warning stops.