HYDRAULICS
8O-57
FLOW TESTS
Follow the directions for each test carefully. The
hydraulic oil must be at normal operating temperature
before performing the test to ensure proper test results.
Read and understand the flow meter directions and
instructions before attempting to test the hydraulic sys-
tem (Figure 8O-7).
Figure 8O-7. Flow Meter and Hydraulic System
Charge Pump Test
The hydrostatic charge pump supplies oil flow to the
steering unit and traction circuit.
1. Shut down the engine and remove the ignition
key.
2. Connect the flow meter IN port to the charge
pump outlet fitting on the traction pump
(Figure 8O-8).
3. Connect flow meter OUT port to the charge pump
outlet hose (Figure 8O-8).
4. Open the tester load valve, set the parking brake,
start the engine, and advance the engine speed to
full throttle.
5. Record the charge pump no load flow indication
(a).
6. Slowly close tester load valve until a reading of
1000 psi (6894 kPa) is obtained, record flow indi-
cation (b).
7. Subtract flow indication (b) from flow indication
(ba. The result is the charge pump leakage.
Conclusion
• If leakage is less that ½ gpm (3.8 lpm), pump is not
at fault. Continue test.
• If leakage is ½ to 1 gpm (3.8 lpm), pump and/or
charge relief valve is marginal. Continue test.
• If leakage is 1 gpm (3.8 lpm) charge pump and/or
steering circuit relief may be faulty. Continue test.
8. Slowly close tester load valve until flow drops off
and pressure stays constant. This is the steering
relief setting which should be 1160 psi (7992 kPa)
+/- 10%.
Conclusion
• If relief pressure is within range, relief and pump are
not at fault.
• If flow and pressure drop off before reaching range,
steering relief or charge pump may be at fault.
NOTE:
The steering relief valve must be replaced as an
assembly.
9. Open tester load valve.
Steering Circuit Test
10.Turn steering wheel completely to the right and
then to the left and hold at each stop. Record
pressure reading in each postion.
Load
Valve
Hydraulic
System
Flow Meter
CAUTION
Do not exceed 1250psi (8618 kPa) during the follow-
ing test.
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