6-46 673831-Rev A
HYDRAULICS
6
Lower Relief Valve Pressure Test
See Figures 6-46 through 6-47.
Before performing this test, perform field test procedures.
(See “Field Test Procedures” on page 6-23.)
1. Operate hydraulic system until oil temperature is
120–150° F (49–65° C).
2. Park the mower safely. (See “Park Mower Safely” on
page 1-6.)
Figure 6-46
3. Remove plug (1) and assemble fitting (2) to “G” test
port on lift valve (3).
4. Connect hose and pressure gauge (4) to fitting (2).
5. Bypass seat switch and engage park brake (park
brake switch in the on position).
Figure 6-47: Lower Relief Valve Pressure Test
Verify engine rpm is within specification (3000 rpm ± 50)
to ensure accurate hydraulic test results.
6. Start engine and run at full throttle (3000 rpm ± 50).
7. Lower the cutting units and hold the lift/lower joystick
in the lower position.
8. Record pressure reading.
9. Stop engine.
Is lower relief pressure 450 ± 10% psi (31 ± 10%
bar)?
YES Lower relief valve is good. Proceed to
step 10.
NO Test lift/steer pump. (See “Lift/Steer Pump
Test” on page 6-47.) Test lift cylinders. (See
“Lift Cylinder Leakage Test” on page 6-23.)
Repair or replace lower relief valve. (See “Lift
Valve” on page 6-53.)
10. Disconnect and remove test equipment. Install all
hoses and fittings as noted prior to removal.
11. Install and connect all components as noted prior to
test.
12. Check hydraulic oil level. Add oil as needed. (Refer to
“Parts and Maintenance Manual” for correct oil
specifications.)
13. Start engine. Check hydraulic system for leaks.
Repair as necessary.
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.
Required Tools and Materials
• Pressure Gauge 500 psi (35 bar)
• Test Hose 500 psi (35 bar)
• -6 ORFS straight fitting
250
psi
BAR
0
5
10
1
5
2
0
2
5
30
3
5
3
0
0
350
4
0
0
450
500
200
150
1
0
0
5
0
0
1
2
3
4
Do not run mower lift system relief valve over
relief longer than 10 seconds, or damage may
occur to hydraulic system components.
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