Relieving Hydraulic System Pressure; Traction Circuit Component Failure - Toro Groundsmaster 4700-D Service Manual

Relieving Hydraulic System Pressure

Before disconnecting or performing any work on the hy-
draulic system, all pressure in the hydraulic system
must be relieved. Park machine on a level surface, lower
cutting decks fully, stop engine and apply parking brake.
To relieve hydraulic pressure in traction circuit, move
traction pedal to both forward and reverse directions. To
relieve hydraulic pressure in steering circuit, rotate
steering wheel in both directions.

Traction Circuit Component Failure

The traction circuit on Groundsmaster 4500--D and
4700--D machines is a closed loop system that includes
the piston (traction) pump, two (2) front wheel motors
and the rear axle motor. If a component in the traction
circuit should fail, debris and contamination from the
failed component will circulate throughout the traction
circuit. This contamination can damage other compo-
nents in the circuit so it must be removed to prevent
additional component failure.
If a component failure occurs in the traction circuit, it is
recommended that the entire traction circuit be disas-
sembled, drained and thoroughly cleaned to ensure that
all contamination is removed from the circuit. If any de-
bris remains in the traction circuit and the machine is op-
erated, the debris can cause additional component
failure.
An alternative method of removing traction circuit con-
tamination would be to temporarily install a high pres-
sure hydraulic oil filter (see Special Tools) into the circuit.
The filter should be used when connecting hydraulic test
gauges in order to test traction circuit components or af-
ter replacing a failed traction circuit component (e.g.
traction (piston) pump or wheel motor). The filter will en-
sure that contaminates are removed from the closed
loop and thus, do not cause additional component dam-
age.
Groundsmaster 4500--D/4700--D
System pressure in mow circuit is relieved when the cut-
ting decks are disengaged (PTO switch in OFF posi-
tion).
To relieve hydraulic pressure in lift circuit, fully lower the
cutting decks to the ground. Turn ignition switch to OFF.
Once the filter has been placed in the circuit, operate the
traction circuit to allow oil flow through the circuit. The fil-
ter will remove contamination from the traction circuit
during circuit operation. The filter can be removed from
the machine after contamination has been removed
from the traction circuit.
IMPORTANT: When operating the traction system
with the high pressure filter installed, make sure
that flow is always directed through the filter before
entering a replaced component (e.g. do not press
the traction pedal in the reverse direction if the filter
is placed for forward direction flow). If flow is re-
versed, debris from the filter will re- -enter the trac-
tion circuit.
NOTE: If traction circuit contamination exists, the trac-
tion pump case drain could allow contaminates to enter
other hydraulic circuits on the machine.
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