OPERATOR'S MANUAL MAINTENANCE

Section E - Hydraulics
Fault Finding
Main Control Valve
E-235 E-235
9803/9880-3
Main Control Valve
Table 1.
Symptoms Possible Causes Countermeasures
Spool sticking 1. Oil temperature is abnormally high. Remove the obstruction.
2. Hydraulic oil is dirty Replace the hydraulic oil and clean the
circuit at the same time.
3. Port connector is tightened too much Check the torque.
4. Valve housing is deformed due to
Installation
Loosen the installation bolt and check.
5. Pressure is too high Attach pressure gauge to pump port and
ram port and check the pressure.
6. Spool is bent Replace the valve assembly.
7. Return spring is damaged Replace the damaged parts.
8. Spring or cap is not on straight Loosen the cap and after aligning, tighten.
9. Temperature inside valve is not even. Warm up the circuit.
Spool does not stroke 1. Valve is clogged inside with dirt Remove the dirt (flushing).
Load cannot be maintained 1. Oil leakage from the ram Check the ram.
2. Oil is by-passing from the valve spool Replace the valve assembly.
3. Oil leakage from the port relief valve Remove the port relief from the housing
and clean the housing seat and relief valve
seat.
4. Oil leakage from the lock valve Disassemble the lock valve and clean the
poppet seat and sleeve, plug seat. If the
seat is damaged, replace the poppet, or lap
the poppet and seat.
When the spool is selected
from neutral to raise position,
the load falls.
1. Foreign matter in load check valve Disassemble the check valve and clean.
2. Check valve poppet or seat damaged Replace the poppet or lap the poppet and
seat part.