John Deere 690DR Excavator Right-Side Propel Issue

[MikePhua]

Introduction
The John Deere 690DR rubber-tired excavator, produced in the early 1990s, is renowned for its versatility and durability. However, like all heavy machinery, it can experience operational challenges. A notable issue reported by operators involves the right-side propel system, where the machine exhibits reduced or no movement on one side, accompanied by unusual hydraulic noises and unintended blade movement. This article delves into the potential causes of this problem and offers troubleshooting steps to address it.
Symptoms of the Propel Issue
Operators have observed the following symptoms:

• The right-side wheels remain stationary despite input from the propel control.
  
• A noticeable decrease in engine RPM and a change in hydraulic pump noise when attempting to move the right side.
  
• The dozer blade descends when the right-side propel control is engaged, regardless of direction.
  
• When the machine is manually pushed, the right-side wheels drag without turning.
  

These symptoms suggest a hydraulic or mechanical malfunction affecting the right-side propel system.
Potential Causes
Several factors could contribute to the observed issues:

1. Hydraulic Swivel Joint Malfunction
   

The hydraulic swivel joint, responsible for transferring hydraulic fluid between the rotating upper structure and the stationary lower frame, can develop internal leaks over time. Such leaks may lead to cross-contamination of hydraulic circuits, causing unintended movements like the blade lowering when the propel control is engaged.

1. Brake Release System Failure
   

Each wheel motor is equipped with a brake that holds the wheels stationary when not in use. A malfunction in the brake release system, such as a failed solenoid or hydraulic valve, can prevent the brake from disengaging, resulting in the wheels not turning. Notably, the John Deere 690 series utilizes separate brake release lines for each side, allowing for isolated testing and diagnosis.

1. Pilot Circuit Leakage
   

The pilot circuit controls various hydraulic functions, including the propel system. High leakage within the pilot circuit can lead to insufficient pressure, affecting the operation of the right-side propel. This issue is more pronounced when the machine operates in a manner that doesn't engage other hydraulic functions, as the pilot circuit isn't adequately charged.

1. Undercarriage Wear
   

Excessive wear in the undercarriage components, such as the drive sprockets, bushings, and chains, can impede the movement of the right-side wheels. While less likely given the machine's low operating hours, it's still a possibility that should be considered.
Troubleshooting Steps
To diagnose and address the issue:

1. Inspect the Hydraulic Swivel Joint
   

Check for signs of external leaks around the swivel joint. If leaks are present, internal contamination may have occurred, necessitating the replacement or repair of the joint.

1. Test the Brake Release System
   

Identify the brake release line for the right-side wheel motor. Using a hydraulic hand pump or auxiliary power source, apply pressure to the brake release line and observe if the wheels begin to turn. If they do, the issue lies within the brake release system.

1. Check the Pilot Circuit
   

Monitor the pressure within the pilot circuit using a pressure gauge. A significant drop in pressure when operating the right-side propel indicates leakage. Inspect components like control valves and pilot lines for wear or damage.

1. Examine the Undercarriage
   

Inspect the undercarriage components for signs of wear or damage. Pay particular attention to the drive sprockets and chains for any irregularities that could hinder movement.
Preventative Maintenance
To prevent future issues:

• Regularly inspect and maintain the hydraulic system, including the swivel joint and brake release components.
  
• Monitor the pilot circuit pressure and address any deviations promptly.
  
• Perform routine checks on the undercarriage to identify and address wear before it leads to operational problems.
  

Conclusion
The right-side propel issue on the John Deere 690DR excavator can stem from various hydraulic and mechanical factors. By systematically diagnosing the problem and addressing the underlying causes, operators can restore full functionality to the machine, ensuring efficient and safe operation. Regular maintenance and timely interventions are key to prolonging the lifespan of this versatile excavator.