Troubleshooting Hydraulic Issues on JLG 600A When Hot

[MikePhua]

Introduction:
The JLG 600A is a popular model of aerial work platforms (AWPs), used in a variety of construction, maintenance, and industrial applications. One common issue that operators encounter with this model is hydraulic failure when the machine becomes hot. Hydraulic systems are essential for the smooth operation of aerial lifts, controlling movements such as lifting, tilting, and extending the boom. When these systems stop functioning properly, particularly in hot conditions, it can lead to delays and safety concerns. In this article, we’ll explore the potential causes of this problem, along with troubleshooting steps and preventative measures to keep the hydraulic system functioning at its best.
Understanding the Hydraulic System in the JLG 600A
Before delving into the causes of hydraulic failure, it’s important to understand how the hydraulic system in the JLG 600A works. This system consists of hydraulic fluid, pumps, valves, cylinders, and hoses, all working together to create the force needed to lift and extend the boom, as well as operate other essential functions. The fluid plays a key role in transmitting power from the pump to the hydraulic cylinders, which in turn perform the lifting and tilting motions.
The hydraulic fluid is pressurized by a pump and routed through various valves and hoses to operate the different movements of the platform. Over time, exposure to high heat or contamination can degrade the fluid and damage components, leading to poor performance or complete failure of the hydraulic system.
Common Causes of Hydraulic Failure When Hot

1. Overheating of Hydraulic Fluid:
   One of the most common reasons for hydraulic systems to fail when the machine becomes hot is overheating of the hydraulic fluid. Hydraulic fluid is designed to operate within a certain temperature range, typically between 100°F and 150°F (37°C to 65°C), depending on the type of fluid and machine specifications.
   • What Happens When It Overheats: When the hydraulic fluid exceeds its maximum temperature, it can lose its viscosity, making it less effective at transmitting power. Overheated fluid can also cause seals to fail, leading to leaks and reduced system efficiency.
     
   • Potential Causes of Overheating:
     • Low Fluid Levels: Insufficient hydraulic fluid can cause the system to overheat as the pump struggles to operate efficiently.
       
     • Clogged Filters: If the hydraulic fluid filters are clogged with debris or contaminants, it can restrict fluid flow, causing overheating.
       
     • Faulty Cooling System: In some cases, the JLG 600A may rely on a heat exchanger or cooling system to maintain proper fluid temperature. If this system fails or is not functioning properly, the hydraulic fluid can overheat.
       
   Real-World Example: An operator working with a JLG 600A lift shared that their machine would stop lifting after extended use on hot days. After inspecting the system, they found that the hydraulic fluid was overheating due to low levels and a clogged filter. After topping off the fluid and replacing the filter, the issue was resolved.
   
2. Contaminated Hydraulic Fluid:
   Another common issue that can affect the hydraulic system is fluid contamination. Contaminants such as dirt, water, or metal shavings can enter the system and cause damage to the hydraulic components. Contaminated fluid can cause pump cavitation, reduce the effectiveness of the fluid, and increase the wear on seals and other components.
   • Sources of Contamination:
     • Improper Maintenance: If the hydraulic fluid is not changed regularly, it can accumulate contaminants over time.
       
     • Leaks in Hoses or Seals: Worn or damaged seals can allow contaminants to enter the system, especially if the lift is used in harsh environments.
       
     • Dirty Environment: Worksites with dust, dirt, or debris can expose the machine to contamination if the hydraulic system is not properly sealed.
       
   • Symptoms of Contaminated Fluid: Contaminated hydraulic fluid can cause erratic machine operation, slower response times, or complete failure of hydraulic movements. In some cases, the fluid may appear cloudy or have an unusual odor.
     
   Story from the Field: An operator in a dusty environment was experiencing slow or unresponsive movement of the JLG 600A’s boom. After conducting a hydraulic oil analysis, they found that the fluid was contaminated with dirt and other particles, reducing the system’s effectiveness. After flushing the system and replacing the fluid, the machine’s performance returned to normal.
   
3. Faulty Hydraulic Pump:
   The hydraulic pump is the heart of the hydraulic system, responsible for pressurizing the fluid and supplying power to the system. If the pump begins to fail, it can cause issues such as reduced hydraulic performance, overheating, or total failure of the system when the machine gets hot.
   • Causes of Pump Failure:
     • Worn Bearings or Components: Over time, the internal components of the pump can wear down, causing a loss of efficiency and overheating.
       
     • Air in the System: Air in the hydraulic lines can prevent the pump from delivering fluid properly, leading to erratic operation and overheating.
       
   Example: A JLG 600A operator experienced a complete loss of hydraulic function after using the machine for extended periods on a hot day. Upon inspection, the hydraulic pump was found to have internal wear, causing a loss of pressure and overheating. Replacing the pump solved the problem.
   
4. Hydraulic Hose or Valve Issues:
   Hydraulic hoses and valves are subject to significant pressure and wear, especially when the machine is in continuous use. Over time, hoses can develop cracks or leaks, causing fluid loss and pressure drops. Similarly, worn or malfunctioning valves can restrict fluid flow and prevent the system from working properly, particularly when it becomes hot.
   • Symptoms of Hose or Valve Failure:
     • Loss of Fluid Pressure: If hoses are leaking or valves are malfunctioning, you may notice a drop in lifting power or slower boom movement.
       
     • Visible Leaks: Check for any visible signs of leaking fluid around the hoses and valves. Leaks can quickly drain the system and cause a complete hydraulic failure.
       
   Real-World Tip: A technician who worked on a JLG 600A with persistent hydraulic issues shared that they found a valve sticking open when the machine got hot. This caused a loss of pressure and prevented the machine from operating as intended. Cleaning and servicing the valve restored normal function.
   

Troubleshooting Hydraulic Failures in Hot Conditions

1. Check Fluid Levels and Condition:
   Start by checking the hydraulic fluid levels and quality. If the fluid is low or appears dirty, top it up or replace it entirely. Ensure that the fluid is the right type for your specific machine and operating conditions.
   
2. Inspect for Leaks:
   Look for visible signs of leaks around hydraulic hoses, valves, and fittings. If you find any, replace the damaged components to prevent fluid loss.
   
3. Clean or Replace Filters:
   Clogged hydraulic filters can lead to overheating and system failure. Clean or replace the filters as needed, ensuring that they are free from debris and contaminants.
   
4. Test the Hydraulic Pump:
   If fluid levels and filters are not the issue, inspect the hydraulic pump for wear or damage. A test of the pump’s output pressure can help identify any underlying issues.
   
5. Check the Cooling System:
   If your JLG 600A has a cooling system to regulate hydraulic fluid temperature, ensure that it’s functioning properly. Clean any debris from the cooling fins and ensure that the coolant is circulating correctly.
   

Preventative Measures to Avoid Future Issues

1. Regular Maintenance:
   To prevent overheating and hydraulic failure, adhere to a regular maintenance schedule that includes fluid checks, filter replacements, and inspections of hoses and pumps.
   
2. Proper Fluid Management:
   Use the manufacturer-recommended hydraulic fluid and replace it according to the service schedule. Ensure that the fluid is clean and free from contaminants.
   
3. Environmental Considerations:
   If operating in hot or dusty environments, consider installing additional filters or dust screens to protect the hydraulic system from contamination. Additionally, avoid running the lift for extended periods in extreme heat whenever possible.
   

Conclusion:
Hydraulic system issues in the JLG 600A, especially when the machine becomes hot, can be caused by several factors, including overheating fluid, contamination, pump failure, or issues with hoses and valves. By carefully troubleshooting the system, operators can identify the root cause and perform the necessary repairs to restore function. Regular maintenance, including fluid checks, filter replacements, and inspection of components, is crucial to preventing these issues from occurring in the first place. With proper care, the JLG 600A’s hydraulic system can continue to perform effectively, even in challenging conditions.