Excavator Track Weakness During Turning and Hydraulic Imbalance

[MikePhua]

The Role of Track Power in Excavator Maneuverability
Excavators rely on independent track drives to rotate, pivot, and reposition with precision. When one track becomes weak or unresponsive during turning, it disrupts not only mobility but also operational safety and productivity. This issue is especially noticeable during counter-rotation or tight turns, where synchronized torque delivery is essential. Weak turning can stem from hydraulic imbalance, motor wear, or control signal failure—and diagnosing it requires a layered approach.
Terminology Notes

• Travel Motor: A hydraulic motor mounted to each track, responsible for propelling the machine forward or backward.
  
• Case Drain Line: A low-pressure return line that carries leakage oil from the motor back to the tank, preventing internal pressure buildup.
  
• Crossline Relief Valve: A valve that limits pressure spikes between opposing hydraulic circuits, protecting components during turning.
  

Common Symptoms of Track Weakness
Operators may observe:

• One track moves slower or hesitates during turns
  
• Machine veers off course when attempting straight travel
  
• Loss of torque or stalling during counter-rotation
  
• Audible whining or vibration from the affected side
  
• Increased fuel consumption due to inefficient movement
  

In one case, a contractor in Alberta reported that their mid-size excavator struggled to turn left under load. After inspecting the travel motor, they discovered a blocked case drain line causing internal pressure buildup and reduced motor efficiency.
Root Causes and Diagnostic Strategy
Track weakness during turning can originate from several sources:

• Hydraulic Motor Wear
  • Worn pistons or seals reduce volumetric efficiency
    
  • Diagnosed via flow testing and temperature monitoring
    
• Case Drain Blockage or Restriction
  • Prevents proper oil return, causing cavitation and overheating
    
  • Confirmed by measuring case drain flow and inspecting hoses
    
• Control Valve Malfunction
  • Sticky or misaligned spool valves disrupt flow balance
    
  • Requires disassembly and bench testing
    
• Crossline Relief Valve Failure
  • Causes pressure spikes or uneven torque delivery
    
  • Inspected by checking relief settings and valve response
    
• Electrical Signal Loss (in electronically controlled systems)
  

• Faulty joystick, sensor, or wiring affects motor command
  
• Diagnosed using multimeter and control module scan
  

A technician in Georgia resolved a similar issue by replacing a cracked crossline relief valve that had been bypassing pressure during left turns. The machine had over 6,000 hours and had operated in rocky terrain without regular hydraulic service.
Repair Procedure and Component Recommendations
To restore full turning power:

• Inspect travel motor for wear and internal leakage
  
• Test case drain flow rate and replace blocked or collapsed hoses
  
• Clean or replace control valve spool and seals
  
• Adjust or replace crossline relief valves to factory spec
  
• Flush hydraulic fluid and replace filters if contamination is found
  
• Calibrate electronic controls if applicable
  

Recommended components:

• OEM travel motor or high-quality remanufactured unit
  
• Case drain hose rated for high-temperature hydraulic return
  
• Crossline relief valve with adjustable pressure settings
  
• Hydraulic filter rated for 10 microns
  
• Diagnostic pressure gauges and flow meters
  

Preventive Maintenance and Long-Term Solutions
To prevent future track imbalance:

• Replace hydraulic fluid every 1,000 hours or annually
  
• Inspect case drain lines and flow monthly
  
• Monitor travel motor temperature during operation
  
• Use fluid analysis to detect early contamination or wear metals
  
• Grease undercarriage components weekly in high-duty cycles
  

Some operators retrofit their machines with external diagnostic ports and pressure sensors to enable real-time monitoring. Others install upgraded relief valves with better thermal stability for extreme environments.
Real-World Anecdotes and Lessons Learned
A demolition crew in Texas shared how their excavator began dragging on the right side during slab removal. After replacing the motor with no improvement, they discovered the issue was a partially blocked case drain line hidden behind a bracket. Clearing the line restored full torque and reduced fuel burn.
In another case, a mining operator in Chile experienced intermittent turning loss during haul road grading. The root cause was a joystick signal dropout due to a frayed wire under the cab. Replacing the harness and recalibrating the control module resolved the issue.
Recommendations for Fleet Managers and Technicians

• Maintain a travel system service log with pressure readings, flow tests, and fault codes
  
• Train operators to recognize early signs of imbalance or noise
  
• Stock spare motors, relief valves, and diagnostic tools for field service
  
• Partner with OEM dealers for updated service bulletins and retrofit kits
  
• Consider proactive motor replacement during major hydraulic service intervals
  

For machines operating in high-duty cycles or extreme climates, consider synthetic hydraulic fluids and enhanced cooling systems to reduce thermal stress.
Conclusion
Weak turning in excavators is often a symptom of deeper hydraulic imbalance or component wear. By applying structured diagnostics and targeted repairs, technicians can restore full mobility and prevent costly downtime. In the rhythm of excavation, turning power is more than movement—it’s control, precision, and confidence. When both tracks pull in harmony, the job flows forward.