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Thursday, August 1, 2013

924G and 924Gz Wheel Loaders Hydraulic System / General Information

General Information

Schematic for the implement system for the 924G Wheel Loader with the VersaLink front end
(1) Coupler
(2) Accumulator for the ride control
(3) Solenoid for the ride control
(4) Combination valve
(5) Tilt cylinder
(6) Lift cylinder
(7) Lines to the third function
(8) Lines to the fourth function
(9) Main control valves
(10) Pilot valves
(11) Connector with an orifice
(12) Screen
(13) Solenoid Valve (hydraulic lockout)
(14) Accumulator for the pilot valves
(15) Pressure reducing valve
(16) Hydraulic tank
(17) Piston pump
(18) Coupler control valve
(19) Manifold
(20) Check valve (return restrictor)
(21) Ball valve (dead engine, lift arm lower)
(A) Test port for the signal pressure of the piston pump for the work tool
(B) Test port for the signal pressure of the piston pump for the steering system
(C) Test port for the piston pump for the work tools
(D) Test port for the steering system
(E) Test port for pilot supply pressure
(F) Pressure switch for the secondary steering
(G) Lines to the steering system
(H) Lines from the relief valve in the steering system
(J) Line from the coupler to the load sensing pressure for the steering system
(K) DUMP
(L) TILT BACK
(M) LOWER
(N) RAISE
(P) Auxiliary
(Q) Auxiliary
(R) Auxiliary
(S) Auxiliary
(T) Line from the service brake
The 924G Wheel Loader hydraulic system is made up of three systems: Implement Hydraulic System, Brake And Fan Drive System and Steering System.
All three systems share a common hydraulic tank. The hydraulic tank is vented.
The location for the hydraulic tank is behind the cab.

The location for the sight glass for the hydraulic oil is in the middle of the machine. View the sight glass from the left side of the machine. Stand on the platform.

Implement Hydraulic System

The implement hydraulic system is composed of the following components: (1) Coupler cylinder, (2) Accumulator for the ride control, (3) Ride control solenoid valve, (4) Combination valve, (5) Tilt cylinder, (6) Lift cylinders, (9) Main control valve, (10) Pilot valve, (12) Screen, (13) Solenoid valve (hydraulic lockout), (14) Accumulator for pilot oil, (15) Pressure reducing valve, (16) Hydraulic tank, (17) Piston pump, (18) Coupler control valve, (19) Manifold, (20) Check valve (return restrictor) and (21) Ball valve (dead engine, lift arm lower).


Left side of the machine(1) Coupler. (2) Accumulator for the ride control. (3) Ride control solenoid valve. (5) Tilt cylinder. (6) Lift cylinders. (17) Piston pump. (16) Hydraulic tank. (18) Coupler control valve. (21) Bypass valve for lowering the loader arms.
Access to the piston pump (17) is achieved by removing panels under the platform. The lift cylinders (6) are mounted under the loader arms in the front frame. The bypass valve (21) for lowering the loader arms is located inside the front frame by the left tower. The ride control solenoid valve (3) is mounted on the left side of the machine.


Right side view of the machine(4) Combination valve. (9) Bank valves. (10) Pilot valves. (12) Screen. (13) Shutoff for the pilot valves. (14) Accumulator for the pilot valves. (15) Pressure reducing valve. (17) Manifold. (20) Check valve.
Access to the pilot accumulator (14) is achieved by opening the door to the engine compartment. Access to the bank valves (9) is achieved by removing an access panel. Access to the pressure reducing valve (15) and access to the combination valve (4) is achieved by removing the access panels under the platform. The manifold (19) is mounted in the center of the machine on the piston pump.


Control levers
(13) Switch for the solenoid valve (hydraulic lockout)
(22) Lift lever
(23) Tilt lever
(24) Auxiliary lever for the third hydraulic function
The implement hydraulic system features control valves that are pilot operated. The control valves are closed center valves. The system is load sensing with a variable displacement pump. The control valves are parallel to each other.
The implement hydraulic system is a pppc system. PPPC stands for the following.

  • Proportional
  • Priority
  • Pressure Compensated
The system only consumes horsepower from the engine as the system requirements are needed.
The 924G uses a box boom construction. Because of the box boom design, the orientation of the tilt cylinder is different from the 924Gz machine.

Braking and Hydraulic Fan System

The braking and hydraulic fan system circulates the oil to the cooler in order to cool the oil in the hydraulic system. Also, the brake and hydraulic fan system provides supply oil to the brake system.
For more information about the specifications for the braking and hydraulic fan system, refer to Service Manual module, RENR6430, "Hydraulic System Specifications".
For more information about the brake and fan drive system, refer to Service Manual module, RENR6428, "Braking and Hydraulic Fan System, Specifications, Systems Operation Testing and Adjusting".

Steering System

The steering system steers the machine by changing the angle of the articulation of the machine. This system also provides oil to the pilot oil system.
For more information about the specifications for the steering systems, refer to Service Manual module, RENR6430, "Hydraulic System Specifications".
For more information about the steering system, refer to Service Manual module, RENR6427, "Steering System, Systems Operation Testing and Adjusting".


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