HYDRAULIC SYSTEM RT540E SERVICE MANUAL
2-8 Published 4-20-2015, Control # 502-01
SUPPLY PRESSURE AND RETURN CIRCUIT
Description
The supply pressure and return circuit is made up of several
circuits which route hydraulic oil from the hydraulic pumps to
the directional control valves for the individual operating
circuits. The supply pressure and return circuit consists of
the reservoir and integral filter, two hydraulic pumps, a
hydraulic oil cooler, and a 12-port hydraulic swivel. Refer to
HYDRAULIC PUMPS in this section for descriptions and
maintenance instructions for each hydraulic pump. Refer to
Section 6 - SWING for description and maintenance
instructions for the 12-port hydraulic swivel.
The supply pressure and return circuit uses Ports 5 and 6 for
pump supply and the dual Port 4 for return. Each operating
circuit’s description and components begin with the circuit’s
directional control valve.
Hydraulic Reservoir and Filter
The reservoir (Figure 2-3), attached to the right side of the
carrier frame, has a capacity of 442.3 l (116.8 gal) total,
395.9 l (104.6 gal) to the full mark. The all-steel reservoir has
an internally mounted full-flow filter and integral baffles that
help cool the hydraulic oil and prevent hydraulic oil foaming.
Hydraulic oil flows through three tubes at the rear of the
reservoir to the three hydraulic pumps. Almost all of the
return flow goes through the filter at the top of the reservoir.
The return line that goes directly into the reservoir (instead of
through the filter) is from the No. 10 port (drain) of the 12-port
swivel.
A magnetized drain plug in the bottom of the reservoir
collects metal particles from the hydraulic oil if it becomes
contaminated.
A sight gauge is located on the front of the reservoir to
indicate hydraulic oil level.
1. A breather/fill cap located on the top of the reservoir
allows air to enter or exhaust the reservoir. It consists of
a breather, fill neck, gaskets and strainer. It is important
that the breather be kept clean to prevent damage to the
reservoir. The breather/fill cap also provides for filling the
reservoir.
A large access cover on top of the reservoir provides for
cleaning. The access cover can also be used to fill the
reservoir after it has been completely drained.
An oil temperature gauge is located on the lower front of the
reservoir to indicate oil temperature.
The hydraulic oil filter (Figure 2-4) is located in the top of the
reservoir. The filter housing contains a replaceable filter
element. Returning hydraulic oil flows through the filter head,
through the filter element and into the reservoir.
An element condition indicator on the filter head indicates
when to change the filter element. When back pressure
caused by a dirty filter element exceeds 172.3 kPa/1.72 bar
(25 psid), the filter head’s bypass feature functions to allow
the hydraulic oil to bypass the filter element and flow into the
reservoir through the bypass outlet instead. A bypass filter
screen prevents gross contamination from passing through
the filter even during bypass. Refer to Return Hydraulic Filter
for filter changing instructions.
Pump Distribution
Pump No. 1 is mounted off drive pads of the torque
converter. Pump No. 2 is mounted on the left front side of the
engine.
Pump No. 1
Pump No. 1 is a variable displacement axial piston pump
with a maximum displacement of 112 cm
3
/rev (6.83 in
3
/rev).
The pump differential or standby pressure is 2413 kPa/24
bar (350 psi). Pump No. 1 supplies oil to the integrated
outrigger/rear steer valve, boom lift, telescope, hoist, brakes
and pilot functions.
Pump No. 2
Pump No. 2 is a single positive displacement gear pump with
a displacement of 39 cm
3
/rev (2.40 in
3
/rev) delivering a
theoretic flow of 84 lpm (21.9 gpm). Pump No. 2 supplies oil
to the front steer and swing circuits.
Pump No. 3
Pump No. 3 is a single positive displacement gear pump with
a displacement of 19 cm
3
/rev (1.16 in
3
/rev) delivering a
theoretic flow of 57.2 lpm (10.6 gpm). Pump No. 3 supplies
oil to the transmission oil cooler fan motor.
Reference Only
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