Main Control Valve Part Numbers 723-47-27500, 723-47-27501, 723-47-27503, 723-47-27507 Compatible with Komatsu PC400-7, PC450-7, PC400-8, PC450-8 excavators Common Faults & Solutions Spool and Valve Bore Wear Symptoms: Weak digging force; performance worsens when hot; boom/arm cylinder drifts; high hydraulic oil temperature Cause: Dirty hydraulic oil scratches spool and valve bore Stuck Spool Symptoms: Heavy joystick, delayed boom, arm, bucket and travel action; no movement