Bobcat 337 Hydraulic Tank Issues and Solutions

[MikePhua]

The Bobcat 337 mini-excavator is known for its compact size, reliability, and versatility in various construction and landscaping tasks. However, like any heavy equipment, it can experience issues over time, particularly with the hydraulic tank and associated hydraulic systems. Problems with the hydraulic tank can lead to a range of performance issues, including sluggish operation, overheating, or even failure of hydraulic components.
In this article, we will delve into the common issues related to the hydraulic tank on the Bobcat 337, provide troubleshooting advice, and discuss solutions to ensure that your excavator runs smoothly.
Understanding the Hydraulic Tank in the Bobcat 337
The hydraulic system in a mini-excavator like the Bobcat 337 is responsible for powering the machine’s primary functions, including digging, lifting, and swinging. The hydraulic tank stores hydraulic fluid that is pumped through the system to various actuators and motors. The performance of the hydraulic system heavily depends on the condition of the hydraulic tank and its components.
The hydraulic tank, or reservoir, plays a key role in filtering and circulating the hydraulic fluid to the hydraulic pump. Over time, contaminants, moisture, or air can compromise the system's efficiency, leading to a range of issues.
Common Problems with the Hydraulic Tank

1. Low Hydraulic Fluid Levels
   One of the most common problems with the hydraulic tank is low fluid levels. This can occur due to leaks in the system or fluid evaporation. When the fluid level is too low, the hydraulic pump may struggle to draw enough fluid, causing reduced performance or even damage to the hydraulic components.
   • Signs of low hydraulic fluid include sluggish operation of the boom, arm, or bucket, increased engine load, and erratic movement of the machine.
     
   • Possible causes of fluid loss: Leaks in hoses, connections, seals, or the tank itself.
     
2. Contaminated Hydraulic Fluid
   Contaminants such as dirt, dust, or water can get into the hydraulic fluid, causing blockages and wear in the system. Water contamination can result in corrosion inside the hydraulic pump, valves, and cylinders, leading to premature failure of critical components.
   • Signs of contamination: Excessive noise in the hydraulic system, inconsistent movement of the boom and arm, or reduced lifting capacity.
     
   • Causes of contamination: Leaky seals, external contaminants entering the hydraulic tank, or improper maintenance practices.
     
3. Hydraulic Fluid Overheating
   Overheating is a common issue with hydraulic systems, especially if the hydraulic tank does not have proper ventilation or cooling mechanisms. Overheated fluid can cause reduced viscosity, which can impair the performance of the hydraulic system and increase wear on components.
   • Signs of overheating: Loss of lifting power, erratic or slow movement, unusual smells (burning fluid), or a hot hydraulic tank.
     
   • Causes of overheating: Blocked cooling fins on the hydraulic oil cooler, inadequate oil circulation, or poor maintenance of the cooling system.
     
4. Hydraulic Tank Leaks
   Leaks in the hydraulic tank can be a major issue, as they lead to fluid loss, reduced system pressure, and potential damage to components. Leaks may develop in the tank itself or in the hoses and seals connecting to it.
   • Signs of leaks: Visible oil on the ground beneath the excavator or around the hydraulic system, fluctuating fluid levels, or poor hydraulic performance.
     
   • Causes of leaks: Cracked tank, worn seals, or loose connections.
     
5. Air in the Hydraulic System
   Air entering the hydraulic system can cause cavitation, which occurs when the fluid is not able to maintain consistent pressure. This can cause irregular movement, excessive noise, and even damage to pumps and motors.
   • Signs of air in the system: Spongy or jerky hydraulic movements, slow or erratic response when engaging the controls, and increased pump noise.
     
   • Causes of air in the system: Leaks in suction lines, faulty seals, or incorrect fluid levels.
     

Troubleshooting the Hydraulic Tank on the Bobcat 337

1. Check Hydraulic Fluid Levels
   Start by checking the hydraulic fluid levels in the tank. Ensure the fluid is at the recommended level indicated in the Bobcat 337 user manual. If the fluid is low, inspect the system for leaks. Tighten any loose connections and replace worn or damaged seals.
   • Tip: Always use the recommended hydraulic fluid type specified in the manual. Mixing fluids can lead to performance issues and increased wear.
     
2. Inspect for Contamination
   If the fluid appears cloudy, dirty, or contains visible particles, it may be contaminated. Perform a hydraulic fluid flush to remove the contaminants from the system. This involves draining the old fluid, replacing the filter, and refilling with clean fluid.
   • Tip: Check the hydraulic filter for blockages or excessive wear. If the filter is clogged, replace it with a new one to maintain proper fluid flow.
     
3. Inspect for Leaks
   Examine the hydraulic tank, hoses, and fittings for any signs of leaks. Check the tank for cracks or signs of wear. If a leak is found, tighten connections or replace damaged parts. For major leaks or damage to the tank, consider replacing the tank.
   • Tip: When checking for leaks, also check the return lines, as they are often overlooked but can contribute to fluid loss.
     
4. Monitor the Cooling System
   Ensure that the hydraulic oil cooler is working properly. Inspect the cooling fins for dirt or debris that could obstruct airflow. If the cooler is clogged, clean it with compressed air or wash it carefully to improve cooling efficiency.
   • Tip: Check the hydraulic system’s temperature gauge regularly to monitor the system’s performance. If overheating persists, check for internal damage to the cooler or improper fluid circulation.
     
5. Bleed Air from the Hydraulic System
   If you suspect air is trapped in the hydraulic system, follow the manufacturer’s procedure to bleed the system. This typically involves operating the machine at idle and engaging the controls to allow any trapped air to escape from the hydraulic cylinders and lines.
   • Tip: Check all seals and connections for wear before bleeding the system to prevent the recurrence of air entry.
     

Solutions to Common Hydraulic Tank Issues

• Low Fluid Levels: Regularly check fluid levels and address any leaks promptly. Refill with the correct hydraulic fluid to avoid system failure.
  
• Contaminated Fluid: Perform regular fluid and filter changes as part of your routine maintenance schedule. Keep the hydraulic tank sealed to prevent contaminants from entering.
  
• Overheating: Ensure the hydraulic oil cooler is functioning properly and maintain regular cleaning of cooling fins. Monitor fluid temperatures closely during operation.
  
• Leaks: Tighten or replace any leaking connections. For a cracked tank, it may be necessary to replace the entire tank to avoid further damage.
  
• Air in the System: Bleed the system to remove air and check for faulty seals that may be allowing air to enter the system.
  

Conclusion
Maintaining the hydraulic tank and system in a Bobcat 337 mini-excavator is crucial for ensuring optimal performance and longevity of the machine. Regular inspection, proper fluid maintenance, and quick troubleshooting can help prevent many common issues such as fluid contamination, leaks, and overheating. By addressing these issues early on, you can avoid costly repairs and downtime, keeping your equipment in excellent working condition.