Troubleshooting the Hitachi EX120 Excavator: Common Problems and Solutions

[MikePhua]

Hitachi's EX120 series excavators have earned a reputation for their durability and reliability in various construction and excavation projects. However, like any piece of heavy machinery, they can experience mechanical issues over time. From hydraulic problems to engine issues, understanding the common faults in the EX120 and knowing how to address them can save operators time and money. This article will discuss some of the most frequent issues faced by EX120 owners and operators, and offer solutions based on user experiences and expert advice.
Common Problems in Hitachi EX120 Excavators

1. Hydraulic System Issues
   

One of the most common complaints among EX120 operators involves the hydraulic system. The hydraulic pump and motors are crucial components that drive the boom, arm, and bucket, and any malfunction here can severely impact the machine's performance.

• Symptom: Reduced lifting power, slow boom or arm movement, or complete hydraulic failure.
  
• Possible Causes: Low hydraulic fluid levels, clogged hydraulic filters, or a malfunctioning hydraulic pump.
  
• Solution: Check and top off hydraulic fluid levels, replace clogged filters, and inspect the hydraulic pump for any signs of wear or damage. Regular maintenance and oil changes are crucial for the longevity of the hydraulic system.
  

A particular story from an operator in a large construction project revealed that frequent hydraulic failures were traced back to old filters and low fluid levels, which had been overlooked during routine checks.

1. Engine Stalling or Poor Performance
   

Another issue that users often face with the EX120 is engine stalling or poor engine performance. The engine could run rough, lack power, or completely stall under load. This can occur during heavy digging tasks, and when it happens, it can stop the work in its tracks.

• Symptom: Engine stalling, rough idling, or low engine power, especially during high load conditions.
  
• Possible Causes: Dirty fuel filters, clogged air filters, or fuel system issues (e.g., air in the fuel lines, bad fuel injectors).
  
• Solution: Replace fuel and air filters regularly, and inspect the fuel system for any leaks or blockages. If stalling persists, it’s worth checking the fuel injectors and ensuring that the engine is getting the proper amount of fuel.
  

In some cases, particularly in harsh weather conditions, operators found that moisture in the fuel line had caused stalling. Adding a fuel water separator and ensuring proper fuel treatment helped resolve the issue.

1. Electrical Failures
   

Electrical issues are another frequent cause of frustration for EX120 owners. These can manifest as erratic behavior in the operator controls, faulty sensors, or an inability to start the machine altogether.

• Symptom: The machine won’t start, warning lights flashing, or malfunctioning electrical systems.
  
• Possible Causes: Dead or weak battery, faulty alternator, or issues with the machine’s wiring.
  
• Solution: Check the battery for charge and corrosion. If the battery is old or the alternator isn’t charging properly, they may need to be replaced. Inspect the electrical wiring and connectors for any loose connections or corrosion, particularly if the machine has been exposed to harsh conditions.
  

A story from a mining site highlights how a seemingly simple electrical issue – a loose wire – caused intermittent problems with starting the machine. After tightening the connections and cleaning the terminals, the issue was resolved.

1. Track and Undercarriage Wear
   

The undercarriage is another critical component that experiences wear, especially when working in tough or uneven terrain. Issues with the track system can result in poor performance, such as reduced mobility and more strain on the machine’s engine.

• Symptom: Uneven track wear, track slippage, or difficulty moving.
  
• Possible Causes: Worn-out sprockets, track rollers, or tension problems.
  
• Solution: Regularly inspect the undercarriage for signs of wear and adjust the track tension as needed. If the sprockets or rollers are excessively worn, they should be replaced to avoid further damage.
  

One operator in a quarry reported that their EX120’s performance improved dramatically after replacing the track rollers and adjusting the tension. This not only helped the machine move better but also decreased overall strain on the engine.

1. Cooling System Issues
   

The cooling system plays a vital role in maintaining engine temperatures. Overheating can lead to serious engine damage, making it essential to regularly check the cooling system for potential problems.

• Symptom: High engine temperature or frequent overheating.
  
• Possible Causes: Low coolant levels, blocked radiator, or malfunctioning thermostat.
  
• Solution: Inspect the radiator for blockages and clean it regularly. Ensure that the coolant levels are topped off and that the thermostat is functioning properly.
  

A fleet manager mentioned that many of their overheating issues were traced to debris blocking the radiator, which prevented airflow and caused excessive engine heat. Simple routine cleaning and checks on the cooling system helped prevent these issues.
Preventive Maintenance Tips for Hitachi EX120 Excavators
Maintaining the Hitachi EX120 is essential for ensuring long-term performance. Preventive maintenance can catch minor problems before they become major issues. Here are a few tips:

1. Regular Fluid Checks: Always check fluid levels—engine oil, hydraulic fluid, coolant, and fuel. Keeping them topped off can prevent many common issues.
   
2. Inspect the Filters: Dirty or clogged filters are a major cause of engine and hydraulic system problems. Regularly replace air, fuel, and hydraulic filters.
   
3. Track Tension Adjustment: Regularly check the track tension to ensure proper movement and prevent unnecessary wear on the undercarriage.
   
4. Battery and Electrical System Checks: Inspect the battery for corrosion and ensure that all electrical connections are secure.
   
5. Routine Cleaning: Dust and dirt can cause parts to wear faster, so regularly clean the radiator, air filters, and other components, especially if working in dirty environments.
   

Real-World Experience: Hitachi EX120 Performance Under Tough Conditions
One particular operator shared an experience where their EX120 performed admirably despite challenging conditions. The machine was frequently used in a demolition project, where it encountered significant dirt, debris, and even concrete dust. The operator made sure to regularly check and clean the filters and cooling system. With consistent preventive maintenance, the EX120 managed to stay in service without major issues for over a year, even in these demanding conditions.
In contrast, a different operator who neglected regular maintenance faced several hydraulic failures and engine stalling issues, ultimately leading to costly repairs and downtime. This highlights the importance of routine inspections and addressing small problems before they escalate.
Conclusion: Maximizing the Lifespan of the Hitachi EX120
The Hitachi EX120 is a highly capable excavator, but like any piece of machinery, it requires regular maintenance and attention to perform at its best. From hydraulic and engine issues to electrical failures and undercarriage wear, staying on top of preventive maintenance can prevent many of the common issues faced by EX120 operators. By addressing problems early and adhering to recommended service schedules, you can ensure your EX120 remains a reliable workhorse for years to come.