How to Fix Kobelco SK200-10 / SK210-10 Boom Up Slow | Full Troubleshooting
Overview
Boom raising slowly is one of the most common hydraulic faults on Kobelco -10 series excavators (SK200-10, SK210-10, SK250-10). This article combines two real repair cases to explain the two main causes and step-by-step solutions:
P2 pump pressure too low → 8-bank Big Arm 3 proportional valve spool stuck
P1 pump oil circuit cut off → 3-bank boom cut-off solenoid or logic valve stuck
Image: Service diagnosis — P1:29.3MPa (normal), P2:15.5MPa (abnormal)
Case 1: P2 Pump Low Pressure (P1 Normal, P2 Only 15.5MPa)
Cause: Big Arm 3 Proportional Valve Sticking (8-bank Solenoid Group)
Enter Service Diagnosis → operate Boom Up → check pressure
P1 pump: 29.4MPa (normal), P2 pump: 15.2MPa (too low)
Do swing relief test: P2 can reach 29.4MPa → pump & unloading valve are normal
Remove the valve spool → found sticking & dirt blockage
Clean spool and valve body → pressure restored, boom speed back to normal
After cleaning the valve spool, replace hydraulic return filter and pilot filter to prevent spool from sticking again.
Image: 8-bank solenoid group — Big Arm 3 proportional valve location
Case 2: P1 Pump Oil Abnormally Cut Off
Cause: 3-bank Boom Cut-off Solenoid / Boom Logic Valve Stuck
When lifting boom: P1 pressure jumps to 33MPa quickly, P2 only 12MPa
P1 pump oil is cut off and does not participate in boom operation
First check 3-bank boom cut-off solenoid
Check if solenoid is wrongly powered on or spool stuck
If solenoid is normal → check boom logic valve
Check logic valve spool sticking or return spring broken
Image: 3-bank solenoid — Boom cut-off solenoid position
Complete Repair Flowchart
Boom up slow → Check pressure in Service Diagnosis
P2 low but swing normal → Clean 8-bank Big Arm 3 proportional valve
P1 oil cut off → Check 3-bank solenoid first, then boom logic valve
Replace filters after hydraulic repair
