1
GENERAL INFORMATION 1.1
Hydraulic System
Oil is drawn from the hydraulic oil reservoir through a
100 micron element. From there it travels to the main
hydraulic pump. (fig. C5003).
•The hydraulic pump is a gear type which is driven by a
shaft and coupler through the hydrostatic drive pump at
engine speed. The oil then flows from the gear pump to
the hydraulic control valve. (C5248).
•The hydraulic control valve is equipped with an
adjustable relief valve which is adjusted to 2200 psi (148
bar). The control valve is a series type with 3 spools
(banks). The various spools activate the boom, bucket and
auxiliary hydraulic functions.
When the spools are in neutral, oil flows from the
hydraulic gear pump, through the control valve and
returns to the 10 micron hydraulic filter. From the
hydraulic filter, the fluid flows to charge the tandem
hydrostatic pump and pressurize the hydraulic brake
release system and then back to the hydraulic reservoir.
Each control valve section spool end contains a centering
spring which returns the spool to neutral when the foot
pedal, or control handle, is released. (fig.C5195).
•The boom section, on foot control operated loaders, has
a detent mechanism to hold the spool in the float position.
The auxiliary section is operated by foot pedal operation,
or may have an optional electrical solenoid operated
control, and may be engaged momentarily by the control
lever mounted switch, forward or reverse, or by engaging
the dash mounted toggle switch for constant power in the
forward direction only.
The system relief valve operates when ever a hydraulic
function has been restricted or overloaded (fig. C5063).
To protect against excessive pressure build up, the relief
valve opens and allows oil to return to the valve outlet.
The system relief valve is adjustable, and is preset at
2200 psi (148 bar).
•Load check valves are located between the ports of each
spool circuit. The function of the load check valve is to
hold the boom arms or bucket in position during initial
spool movement.
1-5
C5003
Control valve location
C5248
Gear pump Location
Relief valve
C5063
C5195
Spring return
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