Bobcat E35 Left Track Won’t Move Indicates Hydraulic or Electrical Disruption

[MikePhua]

The Bobcat E35 and Its Drive System Architecture
The Bobcat E35 is a compact excavator designed for precision digging, trenching, and grading in confined spaces. Introduced as part of Bobcat’s R-Series, the E35 features a zero-tail swing design, advanced hydraulics, and electronically controlled drive motors. With an operating weight around 7,700 lbs and a 33.5 hp diesel engine, it balances maneuverability with breakout force.
The undercarriage uses two independent hydraulic drive motors—one for each track—controlled by joystick input and managed through a central controller. When one track fails to respond, the issue may stem from hydraulic flow restriction, electrical signal loss, or mechanical obstruction.
Terminology Notes

• Drive motor: A hydraulic motor that powers each track independently based on fluid pressure.
  
• Travel solenoid: An electrically actuated valve that enables hydraulic flow to the drive motor.
  
• Joystick controller: The electronic interface that sends directional signals to the travel system.
  
• Case drain line: A low-pressure return line that allows excess fluid and leakage from the motor to return to the tank.
  

Common Causes of One-Sided Track Failure
When the left track won’t move, consider these possibilities:

• Faulty travel solenoid or disconnected wiring
  
• Blocked or kinked hydraulic hose feeding the left motor
  
• Failed drive motor due to internal wear or contamination
  
• Electrical signal loss from joystick or controller
  
• Debris lodged in the sprocket or track frame
  
• Damaged case drain line causing backpressure buildup
  

In many cases, the issue is not catastrophic but results from a minor fault in the control or fluid path.
A Story from the Colorado Rockies
In 2022, a utility crew in Aspen used a Bobcat E35 to trench for fiber optic cable. After a cold morning start, the operator noticed the left track was unresponsive. The machine pivoted right but refused to move left. After checking the hydraulic fluid and inspecting the hoses, the technician discovered a cracked connector on the left travel solenoid. Moisture had entered the plug, causing intermittent signal loss. Replacing the connector and sealing it with dielectric grease restored full function. “It wasn’t the motor—it was the message that never got there,” the operator said.
Diagnostic Strategy for Left Track Inactivity
To isolate the fault:

• Inspect hydraulic fluid level and condition
  
• Check travel solenoid voltage and listen for activation click
  
• Swap solenoid connectors left to right to test signal integrity
  
• Use a pressure gauge to measure output at the left motor port
  
• Inspect hoses for damage, kinks, or loose fittings
  
• Test joystick function and controller output
  
• Manually rotate the track to check for mechanical binding
  

If the motor receives pressure but does not rotate, suspect internal failure. If no pressure is present, trace the signal and valve path upstream.
Repair and Preventive Measures
Depending on findings:

• Replace damaged solenoid or connector with OEM-rated parts
  
• Flush hydraulic lines and replace filters if contamination is found
  
• Rebuild or replace drive motor if scoring or leakage is detected
  
• Clean and lubricate track frame and sprocket
  
• Calibrate joystick and controller if signal drift is present
  
• Install protective boots over connectors in wet environments
  

Always torque fittings to spec and use fluid compatible with Bobcat’s hydraulic system. Avoid mixing connector types or splicing wires without proper shielding.
Maintenance Tips for Reliable Track Function
To prevent future issues:

• Inspect travel solenoids and wiring monthly
  
• Change hydraulic fluid every 1,000 hours or annually
  
• Replace filters every 500 hours
  
• Monitor track response during cold starts and high-load cycles
  
• Keep connectors clean and sealed from moisture
  
• Log voltage and pressure readings during service intervals
  

Some operators install LED indicators to confirm solenoid activation. Others use diagnostic ports for quick pressure checks at the drive motors.
Final Thoughts
When the left track of a Bobcat E35 won’t move, the issue is often electrical or hydraulic—not mechanical. With methodical inspection and respect for the machine’s control logic, the problem can be resolved without major teardown. In compact excavators, motion depends on signal, pressure, and precision. When one link fails, the whole chain stops—but with the right tools and insight, it’s easy to get back on track.