Sakai SV400D-2, Shop Manual

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9-048
HYDRAULIC SYSTEM TROUBLESHOOTING
3-5. Blade (SV400TB/FB-2)
If a problem occurs in the blade control system, determine the cause and carry out action as required,
according to the following general troubleshooting items.
When checking whether or not the pressure is correct, refer to the pressure standard value for
each hydraulic circuit.
3-5-1. Blade up/down operation not possible
Check point Cause Check/Action
1. Oil Level of Hydraulic Oil
Tank
Oil level in hydraulic oil tank is low. Fill the tank until the correct oil level is
obtained.
2. Flow Dividing Valve
(Steering Blade) for
Separation
The oil flow is not divided because the
spool is stuck on one side, interrupting
the hydraulic circuit.
Clean the spool or replace the flow
dividing valve.
3. Blade Circuit Pressure The circuit does not obtain the required
pressure because the setting pressure
of the control valve relief valve is low. Measure the blade circuit pressure. If
low, check the relief valve, and then
adjust or replace the valve.
4. Control Valve The blade cylinder does not operate
because the control valve spool does
not change. If the control valve lever does not move,
check and clean the spool, or replace
the control valve.
5. Blade Cylinder Cylinder thrust decreases due to internal
leakage of the blade cylinder. Repair or replace the blade cylinder.
6. Steering Pump Suction
Filter (also used for
blade circuit)
Steering pump discharge rate decreases
due to clogged filter.
Clean or replace the suction filter.
7. Steering Pump (also
used for blade circuit)
Discharging pressure is insufficient due
to efficiency degradation of steering
pump.
Measure the steering circuit pressure. If
low, replace the steering pump.
3-5-2. Blade movement is slow or force is small
Check point Cause Check/Action
1. Oil Level of Hydraulic Oil
Tank
Oil level in hydraulic oil tank is low. Fill the tank until the correct oil level is
obtained.
2. Control Valve Oil bypasses the passage from the relief
valve because the control valve relief
valve is open. Measure the blade circuit pressure. If
low, check the relief valve, and then
adjust or replace the valve.
3. Blade Cylinder Internal leakage of blade cylinder Repair or replace the blade cylinder.
4. Steering Pump Suction
Filter (also used for
blade circuit)
Steering pump discharge rate decreases
due to clogged filter.
Clean or replace the suction filter.
5. Steering Pump (also
used for blade circuit)
Discharge rate is insufficient due to
efficiency degradation of steering pump.
Measure the steering circuit pressure. If
low, replace the steering pump.