HYDRAULICS
673831-Rev A 6-23
6
Field Test Procedures
When a hydraulic system failure occurs, some simple
effective tests can be performed prior to using a test
instrument. 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 6-27.)
Preliminary Checks
Perform the following checks prior to beginning any tests.
1. Check the hydraulic oil reservoir for proper fluid level,
the presence of air or water, and unusual odor.
2. Check all hoses, tubes, and fittings for leaks. Tighten
as needed.
Eliminate all mechanical issues prior to starting hydraulic
tests.
Lift Cylinder Leakage Test
See Figures 6-12 and 6-13.
Front right lift cylinder is shown; procedure is similar for
all lift cylinders.
1. Start engine. Operate hydraulic system until oil
temperature is at 120–150° F (49–65° C).
2. Raise cutting units.
3. Park the mower safely. (See “Park Mower Safely” on
page 1-6.)
4. Support all cutting unit lift arms.
Figure 6-12
5. Disconnect hose (2) from lift cylinder rod end fitting
(1).
6. Install plug in hose (2).
7. Install cap on lift cylinder fitting (1).
8. Remove support from cutting unit lift arm being
tested.
After 15 minutes, does cutting unit drift down?
YES Cylinder is bypassing oil. Repair or replace
lift cylinder. (See “Lift Cylinders” on
page 6-59.)
NO Repeat the test for all of the lift cylinders. If
all cylinders pass test, the problem may be in
the lift valve. Proceed to step 9.
9. Support all cutting unit lift arms.
10. Connect hose (2) to lift cylinder fitting (1).
11. Start the engine and lower cutting units.
12. Stop the engine.
The hydraulic system is under pressure, and the
oil will be hot.
• Always relieve pressure in the hydraulic
system before performing service.
• Failure to follow appropriate safety
precautions may result in death or serious
injury.
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