Diagnosing and Fixing Slow Travel Issues on the CAT E120B Excavator

[MikePhua]

Introduction: Understanding Travel Performance on the CAT E120B
The CAT E120B excavator is known for its reliability and efficient hydraulic performance, but like all heavy machinery, it can experience issues that affect travel speed and overall productivity. Slow travel speed is a common concern that impacts job efficiency and machine maneuverability on site. This article explores typical causes of slow travel on the CAT E120B, diagnostic steps, temporary and permanent fixes, along with maintenance tips and relevant terminology.
Common Causes of Slow Travel on CAT E120B

• Hydraulic System Problems: Contaminated or low hydraulic fluid, clogged filters, or worn hydraulic pumps.
  
• Travel Motor Wear: Internal damage or wear to travel motors causing reduced output.
  
• Control Valve Issues: Faulty or sticking travel control valves restricting fluid flow.
  
• Track and Undercarriage Problems: Excessive track tension, worn sprockets, or damaged rollers creating mechanical resistance.
  
• Electrical or Sensor Faults: Problems with the electronic travel controls or sensors affecting speed regulation.
  

Technical Terms and Components Explained

• Travel Motor: Hydraulic motor driving the sprockets that move the tracks.
  
• Control Valve: Valve directing hydraulic flow to the travel motors based on operator input.
  
• Hydraulic Filter: Component filtering contaminants from hydraulic fluid to protect system components.
  
• Track Tension: The tightness of the tracks on the undercarriage affecting movement efficiency.
  
• Electronic Control Module (ECM): Computer managing hydraulic and electrical systems, including travel control.
  

Diagnostic Procedures for Slow Travel

• Check hydraulic fluid level and condition; replace or top up if necessary.
  
• Inspect and replace hydraulic filters if clogged or dirty.
  
• Examine travel motors for external damage or leakage.
  
• Test control valves for smooth operation and absence of sticking or internal wear.
  
• Measure track tension and inspect undercarriage components for excessive wear.
  
• Use diagnostic tools to scan ECM for error codes related to travel system.
  

Temporary Fixes and Maintenance Tips

• Ensure hydraulic fluid is clean and at correct levels.
  
• Relieve excessive track tension to manufacturer’s recommended specifications.
  
• Clean or replace filters to restore proper fluid flow.
  
• Lubricate moving undercarriage parts to reduce friction.
  
• Perform regular preventive maintenance to avoid component failure.
  

Case Study: Restoring Travel Speed on a CAT E120B
A contractor noticed the CAT E120B was sluggish in movement during earthmoving tasks. Inspection revealed a clogged hydraulic filter and worn travel motor seals causing pressure loss. After replacing the filter and servicing the travel motors, travel speed and responsiveness significantly improved, reducing operator fatigue and increasing site productivity.
Additional Considerations

• Track wear beyond specification can cause drag, further slowing travel speed.
  
• Operating the machine in harsh environments accelerates wear on hydraulic and mechanical parts.
  
• Use genuine CAT replacement parts for critical components to ensure reliability.
  

Glossary of Terms

• Hydraulic Pressure: Force exerted by fluid in the hydraulic system to perform work.
  
• Seal Leak: Escape of hydraulic fluid through damaged seals reducing system pressure.
  
• Sprocket: Toothed wheel driving the track chain.
  
• Travel Speed Sensor: Device measuring speed to inform the ECM and adjust performance.
  
• Hydraulic Pump: Device that moves hydraulic fluid through the system creating pressure.
  

Conclusion: Maintaining Optimal Travel Performance on the CAT E120B
Slow travel on the CAT E120B excavator can result from various hydraulic, mechanical, or electrical issues. Early diagnosis and a systematic approach to maintenance and repair can restore proper speed and functionality, improving operational efficiency. Understanding the underlying causes and employing preventive maintenance practices help ensure the machine remains productive and reliable in demanding work conditions.