5-34 4252490-Rev A
HYDROSTATIC POWER TRAIN
5
Field Test Procedures
When a hydraulic system failure occurs, some simple
tests can be performed prior to using test instruments.
The results of these tests can lead you to the suspected
component failure. More extensive test procedures,
using test instruments, are presented later in this section.
(See “Instrument Test Procedures” on page 5-35.)
Preliminary Checks
Perform the following checks prior to beginning any tests.
1. Check the hydraulic oil reservoir for improper fluid
level, the presence of air or water, and unusual odor.
2. Check all lines and fittings for leaks. Tighten as
needed.
3. Eliminate all mechanical issues prior to starting
hydraulic tests.
Charge Pump Test
The charge pump supplies oil for charging the traction
circuit and traction pump.
If faults exist in the charge pump, proceed with an
instrument test for the charge pump. (See “Charge
Pressure Test” on page 5-36.)
Traction System Test
See Figure 5-19.
NOTE
Be sure tow valve is closed before beginning traction
system test.
1. Operate hydraulic system until oil temperature is
120–150° F (49–65° C).
Figure 5-19
2. Install wheel restraints (1) to both front wheels.
IMPORTANT
For 3WD models, it is important to lift and support
the rear of the machine, or the machine will move.
3. For 3WD models, lift the machine so that the rear
wheel is off the ground. Support the machine with
jackstands.
4. Release park brake, lower the cutting units, and
move throttle lever to full throttle. Slowly push the
traction pedal forward.
Does the engine labor or stall?
YES The traction pump is not faulty.
NO A fault exists in the hydrostatic drive circuit,
which includes the traction pump and wheel
motors. Proceed to instrument test. (See
“Instrument Test Procedures” on page 5-35.)
TN1761
1
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