Hitachi EX225US Hydraulic System Troubleshooting

[MikePhua]

The Hitachi EX225US is a compact yet powerful crawler excavator, renowned for its efficiency in urban construction and tight-access projects. However, like all complex machinery, it can experience hydraulic system issues that impact performance. One such problem involves intermittent loud banging noises under hydraulic pressure, accompanied by erratic boom and arm movements. This article delves into the potential causes of these issues, diagnostic approaches, and recommended solutions.
Symptoms and Initial Observations
Operators have reported a sporadic loud banging noise in the hydraulic system under pressure, particularly when operating the boom and arm. This noise is often accompanied by violent shaking of the boom and arm when under load. Interestingly, other functions such as the bucket, swing, and travel mechanisms continue to operate normally. This selective malfunction suggests a localized issue within the hydraulic system.
Potential Causes

1. Contaminated Hydraulic Fluid: The presence of metal shavings in the hydraulic fluid can lead to blockages and damage to sensitive components. Such contamination may originate from wear in the hydraulic pump or other internal components.
   
2. Control Valve Malfunction: A faulty or worn control valve can cause irregular pressure distribution, leading to inconsistent hydraulic performance. This could explain the specific malfunctioning of the boom and arm functions while other systems remain unaffected.
   
3. Pressure Imbalance: Fluctuating pressure readings, such as a drop to 0 bar in one line and a spike to 340 bar in another, indicate potential issues with the hydraulic pump or pressure relief valves. These imbalances can result in erratic movements and noises.
   
4. Hydraulic Pump Issues: A failing hydraulic pump may not maintain consistent pressure, leading to overheating and cavitation. This can produce knocking sounds and cause the hydraulic fluid to foam, further exacerbating the problem.
   

Diagnostic Approach

1. Visual Inspection: Begin with a thorough inspection of the hydraulic system for visible signs of leaks, damaged hoses, or worn seals. Check the condition of the hydraulic fluid for contamination or discoloration.
   
2. Pressure Testing: Utilize a pressure gauge to monitor hydraulic pressures at various points in the system. Look for inconsistencies or drops in pressure that could indicate blockages or failing components.
   
3. Component Testing: Isolate and test individual components such as the control valve and hydraulic pump. Listen for unusual noises and check for smooth operation.
   
4. Fluid Analysis: If contamination is suspected, collect a sample of the hydraulic fluid and have it analyzed for metal particles or other contaminants.
   

Recommended Solutions

1. Replace Contaminated Components: If metal shavings are found in the hydraulic fluid, replace the affected components, such as the hydraulic pump or control valve, and thoroughly flush the system to remove all contaminants.
   
2. Repair or Replace Control Valve: A malfunctioning control valve should be either repaired or replaced to restore proper hydraulic function.
   
3. Address Pressure Imbalances: Adjust or replace pressure relief valves to ensure balanced pressure distribution throughout the system.
   
4. Hydraulic Pump Maintenance: If the hydraulic pump is found to be faulty, consider rebuilding or replacing it to prevent further issues.
   

Preventive Measures

1. Regular Maintenance: Adhere to the manufacturer's recommended maintenance schedule, including regular fluid changes and component inspections.
   
2. Use Quality Fluids: Always use the recommended hydraulic fluids and filters to ensure optimal performance and longevity of the hydraulic system.
   
3. Monitor System Performance: Regularly monitor the hydraulic system for any signs of irregularities, such as unusual noises or performance issues, and address them promptly.
   

Conclusion
Hydraulic system issues in the Hitachi EX225US can stem from various sources, including contaminated fluid, control valve malfunctions, pressure imbalances, and pump failures. A systematic diagnostic approach, combined with timely repairs and preventive maintenance, can restore the excavator's performance and prevent future issues. Operators should remain vigilant and proactive in maintaining the hydraulic system to ensure the longevity and reliability of the equipment.