Doosan DX225 Low Hydraulic Pressure: Troubleshooting & Fixes

 

Doosan DX225 Low Hydraulic Pressure – Weak Machine Power Troubleshooting Guide

Low hydraulic pressure on the Doosan DX225 causes weak boom, arm, bucket, swing, and travel performance. This guide explains all symptoms, causes, and step-by-step troubleshooting to restore full hydraulic power.

Component	Target Spec / Action	Common Symptom of Failure
Pilot Pump	35 – 40 Bar	All functions are slow and jerky
Main Relief Valve	Check for contamination	Machine stalls or cannot lift loads
Pump Solenoid	Check Voltage/Resistance	Pump fails to upstroke under load
Hydraulic Oil	Replace every 2,000 hrs	Excessive heat and "foaming" oil

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1. Symptoms of Low Hydraulic Pressure (DX225)

• 
  Weak digging power
• Slow boom, arm, or bucket movement
  
• Machine cannot lift heavy loads
• Travel motor weak, especially on slope
• Swing slow or stops under load
• Engine does not bog down during heavy operation
• Hydraulic functions feel soft or lazy
• High hydraulic oil temperature

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2. Main Causes of Low Hydraulic Pressure on Doosan DX225

A. Hydraulic Pump Problems

• Weak main pump (A/B pump wear)
• Pump not upstroking (low displacement)
• Faulty pump control solenoid
• Incorrect pump standby pressure
• Broken or weak pump regulator spring

B. Hydraulic Oil & Filtration Issues

• Low hydraulic oil level
• Wrong hydraulic oil grade
• Clogged hydraulic return filter
• Clogged pilot filter
• Contaminated hydraulic oil

C. Pilot Pressure Problems

• Low pilot pressure from pilot pump
• Faulty pilot pressure reducing valve
• Joystick pilot signal weak
• Pilot filter clogged

D. Main Control Valve (MCV) Issues

• Spool internal leakage
• Relief valve stuck open
• Relief valve pressure too low
• Center bypass leakage

E. Hydraulic Relief Valve Problems

• Main relief valve weak
• Function relief valves (boom/arm/bucket) weak
• Relief valve contamination

F. Sensor & Electrical Issues

• Pump pressure sensor faulty
• Hydraulic oil temperature sensor faulty
• ECU limiting pump output due to error codes
• Broken wiring to pump control solenoid

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3. Step-by-Step Troubleshooting (DX225 Low Hydraulic Pressure)

Step 1 – Check Hydraulic Oil Level & Condition

• Check oil level with machine on level ground
• Inspect oil color (milky = water contamination)
• Check for burnt smell (overheating)
• Replace oil if contaminated

Low or contaminated oil is the most common cause of weak hydraulics.

Step 2 – Check Hydraulic Filters

• Replace return filter
• Replace pilot filter
• Check suction strainer inside tank

A clogged pilot filter causes slow boom/arm/bucket movement.

Step 3 – Measure Pilot Pressure

• Connect gauge to pilot line
• Check pilot pressure at neutral and during operation
• Adjust pilot pressure if low

Normal pilot pressure: 35–40 bar (varies by model)

Step 4 – Test Main Pump Pressure

• Measure pump standby pressure
• Measure pump working pressure
• Check pump upstroke response
• Check pump control solenoid voltage

If pump does not upstroke, machine will feel very weak.

Step 5 – Check Relief Valve Settings

• Test main relief valve pressure
• Test boom/arm/bucket relief valves
• Clean or replace weak relief valves

Step 6 – Inspect Main Control Valve (MCV)

• Check for internal leakage
• Check spool movement
• Check center bypass leakage
• Check function relief valves

Step 7 – Check Electrical & Sensor Inputs

• Scan for error codes
• Check pump pressure sensor
• Check hydraulic temp sensor
• Check wiring to pump solenoid

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4. Preventive Maintenance

• Replace hydraulic filters every 500 hours
• Use correct hydraulic oil grade
• Check pilot pressure regularly
• Clean hydraulic oil cooler
• Inspect hoses and fittings for leaks
• Service relief valves during major maintenance

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5. Quick Mechanic Tips

• Weak boom only: Boom relief valve or boom spool leakage
• Weak arm only: Arm relief valve or arm spool leakage
• Weak bucket only: Bucket relief valve or linkage issue
• Weak travel: Travel motor or pump output issue
• All functions weak: Main pump or pilot pressure problem

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Conclusion

Low hydraulic pressure on the Doosan DX225 is usually caused by pump wear, pilot pressure issues, clogged filters, relief valve problems, or MCV internal leakage. Following the step-by-step troubleshooting guide above will help you quickly identify the root cause and restore full hydraulic performance.

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