Leaking Bobcat 335 Swing Slew Motor: Troubleshooting and Solutions

[MikePhua]

The Bobcat 335 mini excavator, known for its compact size and impressive digging capabilities, is a staple on many job sites. However, like any piece of heavy equipment, it can experience issues, and one common problem that operators encounter is a leaking swing slew motor. This issue can not only compromise the performance of the excavator but also lead to significant downtime if not addressed promptly. In this article, we’ll explore the causes of a leaking swing slew motor, the steps to diagnose and repair the problem, and some tips for maintaining your Bobcat 335 to avoid future issues.
Understanding the Swing Slew Motor
Before diving into the causes and solutions for a leaking swing slew motor, it’s essential to understand the function of this critical component. The swing slew motor is responsible for enabling the rotational movement of the excavator’s upper structure, allowing it to swing the boom and bucket in various directions. This motor is powered by hydraulic fluid, which provides the necessary force to turn the upper portion of the excavator.
A leak in the swing slew motor can lead to a decrease in hydraulic pressure, affecting the machine’s ability to rotate effectively. Additionally, a loss of hydraulic fluid can lead to system contamination and potential damage to other components, further escalating the repair costs.
Common Causes of a Leaking Swing Slew Motor

1. Worn Seals
   The most common reason for hydraulic leaks in a swing slew motor is worn or damaged seals. Over time, seals that prevent hydraulic fluid from escaping can deteriorate due to the constant pressure and exposure to heat. If a seal fails, hydraulic fluid can leak out, leading to a drop in pressure and affecting the performance of the motor.
   Solution: Inspect the seals around the swing slew motor for signs of wear or damage. If you find any cracks, tears, or compression, the seals will need to be replaced. It’s important to use the correct OEM (original equipment manufacturer) seals for the Bobcat 335 to ensure proper fit and function. Be sure to clean the area thoroughly before replacing the seals to prevent contamination.
   
2. Damaged Hydraulic Hoses
   Another potential cause of leakage is damage to the hydraulic hoses that supply fluid to the swing slew motor. Hydraulic hoses can become worn or punctured over time due to abrasion, impact, or exposure to harsh environments. A damaged hose will allow fluid to leak out, resulting in a loss of pressure and decreased motor function.
   Solution: Inspect all hydraulic hoses leading to the swing slew motor for visible signs of damage, such as cracks, bulges, or fraying. If a hose is damaged, replace it immediately. Ensure that the new hose is properly rated for the pressure levels in the Bobcat 335’s hydraulic system.
   
3. Loose or Damaged Fittings
   Hydraulic systems rely on a series of fittings and connectors to ensure that fluid flows efficiently between components. If these fittings become loose or damaged, they can cause a hydraulic leak. This is especially true around the connections to the swing slew motor.
   Solution: Check all fittings and connectors for tightness. If any fittings are loose, use the appropriate tools to tighten them. If the fittings are damaged or corroded, replace them with new ones. Ensure that the connections are properly torqued to avoid future leaks.
   
4. Contaminated Hydraulic Fluid
   Contaminants in the hydraulic fluid can also cause leaks and damage to seals, hoses, and other components. Dirt, debris, or water can enter the hydraulic system, causing wear on critical components and leading to a loss of pressure. Contaminated fluid can also clog filters and valves, further compromising the system.
   Solution: Regularly check the condition of the hydraulic fluid. If the fluid appears contaminated or has changed color, it’s essential to flush the system and replace the fluid with fresh, clean fluid. Be sure to use the manufacturer’s recommended hydraulic fluid for optimal performance.
   
5. Overpressurized System
   In some cases, a leaking swing slew motor may be the result of an overpressurized hydraulic system. If the pressure exceeds the recommended levels, it can cause the seals and hoses to rupture, leading to fluid leaks.
   Solution: Use a pressure gauge to check the hydraulic system’s pressure. If the pressure is too high, check for any malfunctioning pressure relief valves or other components that might be causing the system to overpressurize. Replace or repair any faulty components to bring the pressure back to the recommended level.
   

Steps for Diagnosing and Repairing the Leak

1. Shut Down the Machine: Safety should always be your first priority. Before attempting any repairs, ensure that the machine is turned off, the hydraulic system is depressurized, and all moving parts are secured.
   
2. Locate the Leak: Identify the source of the leak. This can be done by closely inspecting the swing slew motor and the surrounding hydraulic components for signs of fluid. You may need to use a flashlight or mirror to get a better view of hard-to-reach areas.
   
3. Clean the Area: Once the leak has been identified, thoroughly clean the area around the swing slew motor and hydraulic components. This will help you get a better look at the problem and prevent dirt and debris from entering the system during repairs.
   
4. Replace Worn Components: If you’ve determined that the leak is caused by worn seals, hoses, or fittings, replace the damaged components. Use OEM parts whenever possible to ensure compatibility and performance.
   
5. Refill Hydraulic Fluid: After replacing the faulty components, refill the hydraulic system with the correct type and amount of hydraulic fluid. Be sure to bleed any air from the system to ensure proper fluid circulation.
   
6. Test the System: Start the machine and operate the swing slew motor to test whether the repair was successful. Monitor the motor for any signs of leakage or decreased performance. If the problem persists, double-check your repairs and ensure that all components are properly installed.
   

Maintenance Tips to Prevent Future Leaks
To minimize the risk of hydraulic leaks in the future, here are some essential maintenance tips for the Bobcat 335:

• Regularly inspect seals and hoses: Perform routine checks of the hydraulic system to ensure that seals and hoses are in good condition. Replace any worn components before they fail.
  
• Monitor hydraulic fluid levels: Keep an eye on the hydraulic fluid levels and top them off as needed. Low fluid levels can lead to poor performance and increased wear on the system.
  
• Use clean hydraulic fluid: Always use clean, high-quality hydraulic fluid in your system to prevent contamination and premature wear.
  
• Protect against debris: Keep the machine’s hydraulic components clean and free from dirt, sand, and debris. Use covers or guards to protect hoses and fittings from damage.
  

Conclusion
A leaking swing slew motor on the Bobcat 335 mini excavator can cause significant disruption to your work, but with proper diagnosis and timely repairs, the issue can be resolved efficiently. By understanding the common causes of leaks, such as worn seals, damaged hoses, and contaminated fluid, operators can take proactive steps to address the problem and maintain the hydraulic system’s integrity. Regular maintenance and care will not only extend the life of the swing slew motor but also ensure that your Bobcat 335 continues to operate at peak performance on the job site.