Komatsu D65 85-15 Bulldozer Hydraulic Main Control Valve Assembly Part Numbers: 723-63-24100, 723-63-22600 Common Faults & Troubleshooting Specific action is weak/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