Hitachi ZX350 Hydraulic System Issues and Solutions

[MikePhua]

The Hitachi ZX350 is a powerful and efficient tracked excavator widely used in construction, mining, and demolition applications. Like any heavy machinery, the ZX350’s hydraulic system may face problems over time, leading to decreased performance or even operational failure. This article outlines some common hydraulic system issues that users may encounter with the Hitachi ZX350 and provides practical solutions to resolve them.
Common Hydraulic Issues

1. High Hydraulic Oil Temperature
   One of the most common issues with the hydraulic system is high oil temperature. If the oil gets too hot, it can lead to unstable system pressure and potential damage to hydraulic components. This issue is often caused by poor oil flow, a malfunctioning cooling system, or contaminated hydraulic oil.
   Possible Causes:
   • Cooling system malfunction or blockage.
     
   • Poor quality or insufficient hydraulic oil.
     
   • Obstructions in the hydraulic system restricting oil flow.
     
2. Low Hydraulic Pressure
   A drop in hydraulic pressure can significantly affect the performance of the excavator. Low pressure is often the result of a malfunctioning hydraulic pump, leaks in the hydraulic lines, or a faulty system regulator.
   Possible Causes:
   • Worn-out or damaged hydraulic pump.
     
   • Leaks in hydraulic lines, leading to pressure loss.
     
   • Faulty hydraulic control valves or system regulators.
     
3. Slow or Unresponsive Hydraulic Movements
   If the excavator’s hydraulic movements become sluggish or stop working entirely, the problem is usually related to low hydraulic flow or a failure in the control system. This can be caused by issues with the hydraulic pump, valves, or sensors.
   Possible Causes:
   • Insufficient hydraulic flow from the pump.
     
   • Sticking or improperly adjusted hydraulic control valves.
     
   • Faulty sensors or signal issues in the control system.
     
4. Hydraulic Oil Leaks
   Hydraulic oil leaks can lead to significant performance issues and environmental hazards. Common leak points include hydraulic pumps, hose connections, and cylinder seals.
   Possible Causes:
   • Worn or damaged seals.
     
   • Loose or damaged hose connections.
     
   • Issues with the hydraulic pump itself.
     

Solutions

1. Check the Cooling System
   If the hydraulic oil temperature is too high, the first step is to inspect the cooling system. Clean or replace the cooler if it’s blocked or malfunctioning. Regularly check the oil quality, and make sure the hydraulic oil is of the correct type and at the proper level. If the oil level is low or contaminated, replace it with fresh oil.
   
2. Inspect the Hydraulic Pump and Regulator
   For low hydraulic pressure, start by inspecting the hydraulic pump. If the pump is worn or damaged, it will need to be replaced. Check the hydraulic lines for leaks, and ensure that all connections are tight and secure. If the pressure-regulating valves or system controls are faulty, repair or replace them as needed.
   
3. Examine the Hydraulic Valves and Control System
   If the hydraulic movements are slow or unresponsive, check the hydraulic valves and control system. Ensure that the valves are not sticking or improperly adjusted. Clean or replace the valves if necessary. If the control sensors are malfunctioning, replace the faulty sensors to restore proper operation.
   
4. Address Hydraulic Oil Leaks
   To resolve hydraulic oil leaks, inspect all seals, particularly around the hydraulic cylinders and pumps. If any seals are worn or damaged, replace them immediately. Also, check all hose connections for leaks, and tighten or replace damaged hoses. If the hydraulic pump is leaking, it may need to be serviced or replaced.
   

Preventive Measures

1. Regular Maintenance
   Regular maintenance is key to preventing hydraulic system issues. Regularly check the oil quality, oil levels, and oil temperature to ensure the hydraulic system is in optimal condition. Clean or replace the hydraulic filters and oil as required. Periodic inspection of the cooling system is also essential to keep oil temperatures within acceptable limits.
   
2. Proper Operator Training
   Well-trained operators who understand how to operate the hydraulic system correctly are less likely to cause damage or overload the system. Operators should be trained on how to properly use the excavator and avoid excessive force or improper usage that could harm the hydraulic components.
   
3. Use High-Quality Hydraulic Oil
   Always use high-quality hydraulic oil that meets the manufacturer's specifications. Poor-quality oil can cause excessive wear and contamination in the hydraulic system. Regularly replace the oil according to the manufacturer’s recommendations to maintain system performance.
   

Conclusion
The Hitachi ZX350’s hydraulic system is a vital part of its high performance, but like any other system, it can experience issues such as high oil temperature, low pressure, sluggish movements, and oil leaks. Regular inspections, maintenance, and timely repairs can help prevent these issues. By maintaining proper hydraulic oil levels, using quality oil, training operators, and checking for leaks or component failures, you can ensure that the hydraulic system runs smoothly and prolong the life of your machine.