Bulldozer Komatsu D65E-12 D85E-12 D85ESS-2 Main Control Valve Assembly – Part Number 723-63-12101 723-63-12100
Common Faults & Troubleshooting
Specific action is weak or not working: Stuck spool in that section, spool/sleeve wear causing internal leakage, damaged O-rings. First measure the outlet pressure of that section to diagnose.
All actions are weak: Usually caused by insufficient main pump pressure or a failed main Relief Valve pressure setting. Check system pressure first before disassembling the valve.
Erratic or jittery movement: Stuck spool, fatigued springs, unstable pilot control pressure, contaminated oil.
Oil leakage: Aged O-rings on valve body joints and spool seals, causing external seepage or internal leakage.
High oil temperature: Excessive internal leakage in the valve group, abnormal throttling.
Repair & Purchasing Recommendations
Minor faults: Clean the spool, replace the O-ring seal kit, lap the spool.
Scored spool or worn sleeve: Replace the spool parts or the complete valve assembly.
When ordering: Confirm the specific sub-model and the original old part number.