How to Fix Slow Bucket Cylinder Movement on Kobelco Excavator
Step 1: Electronic Diagnostic via Monitor
First, we must determine if the sensors are sending correct signals. Access the service menu (Hold Buzzer Switch + Turn Key ON) and navigate to Page 6 to check C-2 PUMP 2 pressure.
[Monitor Page 6 - C-2 Pump Data Screenshot]
- Engine OFF : Pressure should be 0.0 MPa.
- Abnormal : If it shows 5.0 - 8.0 MPa with engine off, the High-Pressure Sensor is faulty.
Step 2: Inspect the Bucket Cylinder 2-Speed Solenoid
The 2-speed solenoid is responsible for high-speed flow. If the sensor is fine, check the current of the "D-6 ARM IN-2-SPEED" on Page 7 of the monitor.
| Condition | Standard Current |
| During Cylinder Retraction | Approx. 400 mA |
| Cylinder Overflow/End Stroke | Approx. 200 mA |
If the current is abnormal, replace the solenoid valve. We recommend using original parts (e.g., Part No. 40C50) for maximum reliability.
Step 3: Check the Mechanical Valve Spool
Remove the valve cover and pull out the spool. Look for wear, scratches, or sticking caused by hydraulic contamination. A jammed spool will block the auxiliary oil flow, slowing down the bucket arm cylinder.
