Diagnosing Hydraulic Leaks on the John Deere 690E LC: Rotary Swivel vs. Swing Motor

[MikePhua]

Hydraulic leaks on excavators can significantly affect their performance and lead to costly repairs if not promptly addressed. The John Deere 690E LC is a robust and reliable piece of machinery, but like any heavy equipment, it can experience hydraulic issues over time. One of the more common problems is identifying the source of a hydraulic leak, particularly in systems like the rotary swivel or swing motor. Understanding how to troubleshoot and identify the exact cause of the leak is crucial for efficient repair and minimizing downtime.
In this guide, we will walk through the steps to diagnose whether the hydraulic leak on a John Deere 690E LC is originating from the rotary swivel or the swing motor, as well as provide insights on how to handle such issues.
Understanding the Hydraulic System of the John Deere 690E LC
The John Deere 690E LC, a large and powerful hydraulic excavator, is equipped with a complex hydraulic system that drives a variety of functions, including the swing mechanism. This system relies on two primary components for rotational movement: the rotary swivel and the swing motor.

• Rotary Swivel: The rotary swivel is a key component that allows for the rotation of the upper structure of the excavator (the house) relative to the lower structure (the undercarriage). It provides the hydraulic connection between the upper and lower parts of the excavator, enabling continuous rotation.
  
• Swing Motor: The swing motor is responsible for driving the swing function, allowing the upper structure to rotate. It works in conjunction with the rotary swivel and is powered by the hydraulic fluid from the swing circuit.
  

When diagnosing a hydraulic leak, it's essential to determine whether the issue is with the rotary swivel or the swing motor, as the repairs or replacements may differ.
Identifying the Symptoms of a Hydraulic Leak
Before diving into troubleshooting, it’s important to recognize the signs of a hydraulic leak. Some common symptoms of a hydraulic leak include:

• Visible Fluid Leaks: Oil or hydraulic fluid around the swing area or the base of the swing motor or rotary swivel is often the first sign of a hydraulic issue.
  
• Decreased Swing Function: If the swing motor or rotation becomes sluggish or unresponsive, it may be due to a loss of hydraulic pressure caused by the leak.
  
• Erratic Movement: Irregular swing movements or difficulty controlling the swing speed could also be related to fluid loss, particularly if pressure is not being maintained correctly.
  

Step-by-Step Diagnosis: Rotary Swivel vs. Swing Motor
To effectively diagnose the source of a hydraulic leak on a John Deere 690E LC, follow these steps to narrow down whether the leak is coming from the rotary swivel or the swing motor.
1. Inspect the Swing Motor
The swing motor is a critical component of the excavator's swing function. A leak in the swing motor can lead to a significant loss of hydraulic pressure and impaired swing movement.

• Visual Inspection: Start by performing a visual inspection of the swing motor area. Look for any visible signs of fluid leaking from the motor itself or from the hydraulic lines attached to it.
  • Common symptoms of a swing motor leak include fluid dripping from around the motor housing or from the seals at the point where the motor connects to the swing bearing.
    
• Check for Fluid Loss: If the fluid loss is localized around the motor area and is accompanied by sluggish or erratic swing operation, the leak is likely from the swing motor. Additionally, a loss of swing motor performance—such as difficulty in maintaining a consistent swing speed—can indicate a problem with the motor or its seals.
  
• Pressure Test: If visible leaks are not immediately apparent, a pressure test can help determine if there is a loss of pressure within the swing motor. Low pressure readings on the swing circuit could indicate an issue with the motor’s internal seals or other components.
  

2. Inspect the Rotary Swivel
The rotary swivel connects the upper and lower parts of the excavator and allows for continuous rotation. A leak in the rotary swivel is often less obvious than a swing motor leak, as the swivel is hidden behind the swing motor and may require more detailed inspection.

• Visual Inspection: Examine the area where the swing motor and rotary swivel connect. Look for signs of hydraulic fluid accumulation around the base of the swivel. In many cases, a rotary swivel leak may result in fluid seeping out from the joint between the upper and lower parts of the machine.
  
• Listen for Unusual Sounds: When the hydraulic system is leaking at the rotary swivel, you might hear an unusual hissing or whistling sound. This is due to the escaping pressurized fluid. Pay attention to any sounds coming from the swivel when the machine is in operation.
  
• Check for Excessive Play: If the rotary swivel is leaking, it may cause excessive play or slop in the swing mechanism. This can result in an uneven or jerky swing, as the system is unable to maintain consistent hydraulic pressure.
  
• Pressure Test: Just like with the swing motor, a pressure test can help identify a leak in the rotary swivel. Low pressure in the swivel circuit, especially when combined with fluid loss, strongly suggests a failure of the rotary swivel seals or internal components.
  

3. Check for Leaks at the Hoses and Fittings
Leaks can also occur in the hoses and fittings connecting the rotary swivel or swing motor to the hydraulic system. Over time, these hoses may degrade, crack, or loosen, leading to hydraulic fluid leakage.

• Hose Inspection: Examine all hoses connected to the swing motor and rotary swivel for signs of wear, cracking, or abrasion. Ensure that the hoses are securely connected and that fittings are not loose.
  
• Hydraulic Fittings: Check the hydraulic fittings where hoses connect to the motor and swivel. Loose or damaged fittings can result in hydraulic fluid leaking under pressure.
  

4. Conduct a System Pressure Test
A pressure test is one of the most effective ways to identify whether the leak is coming from the swing motor or the rotary swivel. A qualified technician can use a gauge to measure the pressure in each part of the hydraulic circuit.

• Swing Circuit Test: By testing the swing circuit, it’s possible to determine if there’s a pressure drop indicative of a leak in either the swing motor or the rotary swivel.
  
• Rotary Swivel Circuit Test: If the swing circuit pressure is stable but the leak persists, it suggests that the issue lies within the rotary swivel. If both circuits are affected, further investigation will be required to locate the exact source.
  

Repairing the Hydraulic Leak: Swing Motor vs. Rotary Swivel
Once the source of the leak has been identified, repairs can begin. The approach will vary depending on whether the issue lies with the swing motor or rotary swivel.

• Swing Motor Repair: If the leak is found in the swing motor, the motor may need to be disassembled, and worn seals or internal components may need to be replaced. In some cases, it may be more cost-effective to replace the entire swing motor, especially if it has sustained significant damage.
  
• Rotary Swivel Repair: If the leak is located in the rotary swivel, repairs will likely involve replacing the seals or O-rings that are allowing fluid to escape. In some cases, the entire rotary swivel assembly may need to be replaced if it is damaged beyond repair.
  

Preventive Maintenance to Avoid Hydraulic Leaks
Regular maintenance of the hydraulic system is essential to prolong the life of the swing motor, rotary swivel, and associated components. Here are some preventive measures to help reduce the likelihood of hydraulic leaks:

1. Routine Fluid Checks: Regularly monitor hydraulic fluid levels and inspect for signs of contamination or degradation. Low fluid levels can exacerbate leaks and lead to more significant hydraulic system failures.
   
2. Seal Inspections: Check all hydraulic seals for signs of wear, cracking, or damage. Seals are critical for maintaining hydraulic pressure and preventing leaks.
   
3. Hose and Fitting Maintenance: Periodically inspect hoses and fittings for wear and ensure that all connections are tight. Replace any damaged hoses promptly.
   
4. Pressure Testing: Regularly perform pressure tests on the hydraulic circuits to ensure that the system is operating at the correct pressure. Low pressure can indicate issues with the swing motor, rotary swivel, or other hydraulic components.
   

Conclusion
Diagnosing and repairing hydraulic leaks in the John Deere 690E LC requires careful inspection and a methodical approach to pinpoint the source of the issue. By understanding the function of the rotary swivel and swing motor, operators and technicians can effectively troubleshoot leaks and implement the appropriate repairs. Regular maintenance and timely repairs are key to keeping the hydraulic system in optimal working condition and ensuring the longevity and performance of the machine.