How to Fix Kobelco Swing Motor One Side Unbrakable & Weak | Main Relief Valve Adjustment
1. Fault Symptom & Root Cause
Common failure of Kobelco excavator swing motor:
One side swing cannot brake (unbrakable)
One side swing weak / slow / low pressure
Root cause: Swing main relief valve pressure abnormal or damaged.
2. Standard Pressure: 290 kg/cm² (290 bar)
Standard pressure for Kobelco swing main relief valve:
290 kg/cm² (290 bar)
3. How to Adjust Swing Main Relief Valve Pressure
Tools: 38 mm wrench, 30 mm wrench
Loosen the lock nut (38 mm)
Mark the screw position before adjustment
Turn clockwise to increase pressure
Turn counterclockwise to decrease pressure
Adjust to 290 kg
4. How to Confirm Relief Valve Fault (Swap Test)
Remove left and right swing main relief valves
Swap and install them
Test swing function
If fault moves to the other side → relief valve is broken
5. Internal Faults of Relief Valve
Valve core & spool wear → internal leakage
Spring fatigue
Oil hole blocked by dirt
Once worn, cannot be repaired — must replace the assembly.
