Doosan DX225 Bucket Slow or Weak: Hydraulic Pressure & Repair Guide

 

Doosan DX225 Bucket Slow or Weak – Technician-Level Troubleshooting Guide

This guide explains the hydraulic causes and technician-level troubleshooting steps for a bucket slow or weak condition on the Doosan DX225 / DX225LC hydraulic excavator.

Test Point	Pressure Specification	Adjustment Method
Pilot Pump Outlet	40 ± 5 bar	Regulator Screw
Main Pump (Stall)	330 bar	Main Relief Valve
Power Boost	350 bar	Solenoid Logic
Joystick Signal	23.5 ± 1.5 bar	Pilot Valve

1. Bucket Hydraulic System Overview

• Main hydraulic pumps (P1 / P2)
• Pilot control system
• Main control valve bucket section
• Bucket cylinder
• Power mode / power boost logic
• Priority and LS circuits

2. Required Tools and Conditions

• 600 bar pressure gauge
• Pilot pressure gauge (0–60 bar)
• Flow meter
• Thermometer
• Two technicians
• PPE (gloves, eye protection)

3. Safety Precautions

• Park on level ground
• Warm hydraulic oil to operating temperature
• Clear the working area
• Use two people during pressure tests
• Follow manufacturer safety rules

4. Hydraulic Pressure Specifications

4.1 Pilot Pressure

• Pilot pump outlet: 40 ± 5 bar
• Joystick pilot line: 23.5 ± 1.5 bar

Adjustment: Turn screw clockwise to increase, counterclockwise to decrease.

4.2 Main Pump Pressures (Power Mode)

Condition	Main Pressure	Pilot Pressure
Neutral	20–40 bar	30 bar +10 bar
Cylinder Stall	330 bar +5 bar	30 bar +10 bar
Stall + Power Boost	350 bar +10 bar	30 bar +10 bar

4.3 Swing Priority Valve

• Digging mode: 0 bar
• Trenching mode: 20–40 bar

5. Step-by-Step Troubleshooting

Step 1 – Check Pilot Pressure

• Normal: 23.5 ± 1.5 bar
• If low: adjust regulator, clean pilot filter, check leaks

Step 2 – Check Main Pump Pressure

• Normal stall: 330 bar
• Power boost: 350 bar
• If low: adjust pump regulator, check relief valve, inspect pump

Step 3 – Check Bucket Control Valve

• Spool sticking
• Internal leakage
• Weak relief valve
• Regen valve stuck

Step 4 – Check Bucket Cylinder

• Rod seal leakage
• Internal bypass
• Scoring inside cylinder

Step 5 – Check Flow & LS Circuit

• Use flow meter if pressure is correct but bucket is slow
• Check LS line
• Check swing priority valve

6. Common Causes & Fixes

• Low pilot pressure → adjust regulator
• Low main pressure → adjust pump, check relief valve
• Valve leakage → clean or overhaul
• Cylinder bypass → rebuild cylinder
• LS signal issue → repair LS line

7. Technician Notes

• Always test with warm oil
• Check pilot pressure first
• Use flow meter for pump adjustments
• Document all readings

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