TM 5-3805-290-23-1
THEORY OF OPERATION - CONTINUED
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HYDRAULIC SYSTEM
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1.
General.
a.
Schematic for 924G Wheel Loader implement system is located in (WP 0210 00).
b.
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. Hydraulic tank is vented.
System only consumes horsepower from engine as required.
c.
Implement Hydraulic System.
(1)
Implement hydraulic system is composed of coupler cylinder, ride control accumulator, ride control sole-
noid valve, combination valve, tilt cylinder, lift cylinders, main control valve, pilot valve, screen, solenoid
valve (hydraulic lockout), oil pilot accumulator, pressure reducing valve, hydraulic tank, piston pump,
coupler control valve, manifold, check valve (return restrictor), ball valve (dead engine, lift arm lower),
coupler, ride control solenoid valve, tilt cylinder, lift cylinders, bypass valve for lowering loader arms,
bank valves, pilot valves, screen, shutoff for pilot valves, pilot valves accumulator, and control levers.
(2)
Access piston pump by removing panels under platform. Lift cylinders are mounted under loader arms in
front frame. Bypass valve for lowering loader arms is located inside front frame by left tower. Ride control
solenoid valve is mounted on left side of machine.
(3)
Access to pilot accumulator by opening door to engine compartment. Access to bank valves by removing
an access panel. Access pressure reducing valve and combination valve by removing access panels under
platform. Manifold is mounted in center of machine on piston pump.
(4)
Implement hydraulic system features pilot-operated control valves. Control valves are closed center
valves. System is load sensing with a variable displacement pump. Control valves are parallel. Implement
hydraulic system is a Proportional, Priority, Pressure-Compensated (PPPC) System.
d.
Braking and Hydraulic Fan System. Braking and hydraulic fan system circulates oil to cooler, to cool oil in
hydraulic system. Also, brake and hydraulic fan system provides supply oil to brake system.
e.
Steering System. Steering system steers machine by changing angle of articulation of machine. This system also
provides oil to pilot oil system.
2.
Oil Filter (Hydraulic).
a.
Pressure oil from braking and hydraulic fan pump goes into fan motor, then to cooler. Then, hydraulic oil flows
through inlet line to filter. Oil flows through outlet line to tank.
b.
During normal operation, oil goes through filter element and out through outlet line. Hydraulic tank filter element
stops any debris in oil. If filter element becomes full of debris, restriction to flow of oil causes a pressure increase
inside filter. Pressure oil then causes bypass valve, located in filter housing, to move against force of spring. Oil
then goes past open bypass valve and into hydraulic tank. When hydraulic oil is cold, increased pressure from cold
hydraulic oil can also cause bypass valve to open. When hydraulic oil heats up, hydraulic oil pressure drops. Drop
in hydraulic oil pressure closes bypass valve.
