Toro Groundsmaster 3500 30807 Service Manual page 97

Traction Circuit Testing − Wheel Motor Efficiency
Test:
Wheel motor efficiency is the second in a series of tests
recommended to determine traction circuit perform-
ance. Hydraulic fluid flow of 1.5 GPM (5.7 LPM) or more
through a stationary wheel motor under load indicates
an internal leak in the wheel motor. A worn wheel motor
is less efficient. Eventually, enough fluid by−pass will
cause the wheel motor to stall under heavy load condi-
tions. Continued operation can generate excessive
heat, cause damage to seals and other components in
the hydraulic system, and affect overall machine per-
formance.
There are moments during wheel motor operation (ger-
oller position) when fluid flow through the motor is less
restricted. If a wheel motor is tested in this position, the
test results will be higher should not be used to determ-
ine wheel motor efficiency. Test wheel motors in three
(3) different wheel positions to obtain accurate test res-
ults. Record test readings for all three (3) wheel posi-
tions.
Hydraulic fluid flows through both front wheel motors (in
parallel) before passing through the rear wheel motor (in
series). In this configuration, the rear wheel motor can
mask front wheel motor performance issues, and the
front wheel motors can mask rear wheel motor perform-
ance issues. Start by testing both front wheel motors to-
gether, then individually if necessary. Finish by testing
the rear wheel motor.
Special Equipment Required:
S Pressure Gauge
S Flow Meter with Pressure Gauge that has at least
an 18 GPM (68 LPM) capacity.
S Phototach (non−contact tachometer).
1. Park machine on a level surface with the cutting units
lowered and the PTO switch off. The engine should be
off and the parking brake engaged.
2. Read Precautions for Hydraulic Testing in this
chapter.
3. Make sure that traction pedal is adjusted to the neu-
tral position.
4. Attach a heavy chain to the rear of the machine frame
and an immovable object to prevent the machine from
moving during testing.
Front Wheel Motor Test:s
Hydraulic fluid flows through both front wheel motors (in
parallel) before passing through the rear wheel motor (in
series). To accurately test the front wheel motors, the
rear wheel motor must be removed from the traction cir-
cuit.
Groundsmaster 3500
1
1. Lower hydraulic fitting
1. Disconnect hose from the lower hydraulic fitting on
the bottom of the hydrostat (Fig. 27).
NOTE: An alternate testing location would be at the hy-
draulic hose from the hydrostat and the hydraulic tube
supplying the front wheel motors under the left floor
plate.
2. Install flow tester between the hydrostat and the dis-
connected hose. Make sure the tester flow control valve
is fully open.
3. Disconnect both hydraulic lines from the rear wheel
motor, then reconnect the lines to each other. Plug ports
in wheel motor to prevent contamination.
4. Chock front wheels to prevent wheel rotation.
5. Start engine. Move throttle to full speed (Diesel en-
gine = 3220 + 50 RPM, Gas engine = 3420 + 30 RPM).
6. Make sure hydraulic fluid is at normal operating tem-
perature by operating the machine for approximately 10
minutes. Make sure the hydraulic tank is full.
7. Verify with a phototach that the pump speed is ap-
proximately 2850 RPM.
Use extreme caution when performing wheel mo-
tor tests. The wheel motors will be trying to move
the machine forward.
8. Sit in the operators seat, release the parking brake,
and set the Transport/Mow slide to the transport posi-
tion.
9. Slowly depress forward traction pedal until 1000 to
1500 PSI (68.9 to 103.4 Bar) is displayed on the pres-
sure gauge.
Flow meter should read less than 1.5 GPM (5.7
LPM).
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Figure 27
2. Piston pump
CAUTION
Hydraulic System