International 520B Transmission Charge Pump Issues and Solutions

[MikePhua]

The International 520B is a versatile and durable tractor loader, widely used in construction and agricultural applications. However, like all heavy equipment, it can encounter issues that require troubleshooting and maintenance. One such issue is a transmission charge pump failure, which can severely affect the machine’s performance and efficiency. Understanding the role of the charge pump, the causes of failure, and how to fix it can help operators extend the life of their equipment and avoid costly repairs.
Background of International Harvester and the 520B
International Harvester (IH), founded in 1902, was a leader in manufacturing agricultural and construction machinery. Over the years, it became known for producing durable and innovative machines, with the 520B loader being one of its significant contributions to the heavy equipment market. Though IH ceased operations in the 1980s, the legacy of its machines, including the 520B, continues to be felt in the industry.
The International 520B was designed to tackle a variety of tasks, from digging trenches to loading materials and moving heavy objects. It features a powerful engine and a robust transmission system, making it ideal for tough construction sites. However, as with all mechanical systems, maintenance and proper understanding of its components are crucial to maintaining its efficiency.
What is a Transmission Charge Pump?
The transmission charge pump is an integral part of the hydraulic system in machines like the International 520B. It is responsible for circulating hydraulic fluid throughout the transmission to maintain pressure and proper operation. Without sufficient hydraulic pressure, the transmission cannot shift properly, leading to poor machine performance or complete failure of the transmission system.
The charge pump ensures that hydraulic fluid is supplied at the right pressure, preventing damage to the transmission components. If the pump fails, it can result in erratic shifting, loss of power, or complete transmission failure. The 520B loader, with its complex hydraulic and transmission systems, depends heavily on a properly functioning charge pump.
Common Causes of Transmission Charge Pump Failures
Several factors can lead to the failure of the charge pump in the International 520B. Here are some common causes:

1. Low Hydraulic Fluid Levels: One of the most frequent causes of charge pump failure is low or contaminated hydraulic fluid. If the fluid levels drop too low, the pump cannot function correctly, leading to a loss of hydraulic pressure.
   
2. Contaminants in Hydraulic Fluid: Dirt, debris, or moisture can enter the hydraulic system and cause blockages or damage to the pump. Contaminants can also cause the fluid to break down, reducing its lubricating and cooling properties.
   
3. Aging or Worn Pump Components: Over time, the internal components of the charge pump, such as seals and gears, can wear out. This wear and tear can lead to insufficient fluid pressure, resulting in transmission issues.
   
4. Faulty Relief Valve: The relief valve regulates the pressure within the hydraulic system. If the valve malfunctions, it can cause excessive pressure, damaging the charge pump and other hydraulic components.
   
5. Electrical Issues: In some cases, electrical problems, such as faulty sensors or wiring, can interfere with the pump's operation. If the electrical system fails to send the correct signals to the pump, it may not function correctly.
   

Diagnosing Charge Pump Failures in the 520B
Diagnosing a transmission charge pump failure in the International 520B requires a systematic approach. Operators or technicians should follow these steps:

1. Check Hydraulic Fluid Levels and Quality: Start by inspecting the hydraulic fluid levels. If the fluid is low, top it up with the recommended type. If the fluid appears dirty or contaminated, it may need to be replaced. Contaminated fluid should be flushed from the system.
   
2. Inspect for Leaks: Hydraulic fluid leaks can reduce pressure and lead to pump failure. Inspect hoses, seals, and fittings for signs of leakage. Replace any damaged components immediately.
   
3. Listen for Abnormal Sounds: A faulty charge pump may produce unusual noises such as whining or grinding. These sounds indicate that the pump is under strain or that its internal components are damaged.
   
4. Test the Pressure Relief Valve: The pressure relief valve should be checked for proper function. If the valve is stuck open or closed, it can cause pressure problems that affect the charge pump.
   
5. Monitor Pump Performance: If the loader is experiencing poor hydraulic performance, such as delayed shifting or slow response times, the charge pump may not be generating sufficient pressure. This can be confirmed using a pressure gauge to check the fluid pressure in the system.
   

Replacing the Transmission Charge Pump
If the diagnosis points to a faulty transmission charge pump, it will need to be replaced. The process generally involves the following steps:

1. Disconnect the Battery: Always disconnect the machine’s battery before performing any work on the hydraulic system to avoid electrical hazards.
   
2. Drain Hydraulic Fluid: Before removing the charge pump, drain the hydraulic fluid from the system. Be sure to dispose of the fluid properly.
   
3. Remove the Old Charge Pump: Access the pump by removing any components that obstruct it, such as covers or protective shields. Loosen and remove the pump mounting bolts, and then carefully extract the old pump from the transmission.
   
4. Install the New Pump: Install the new charge pump in reverse order, ensuring that it is securely mounted and aligned with the system. Be sure to replace any seals and gaskets to prevent leaks.
   
5. Refill Hydraulic Fluid: After the new pump is installed, refill the hydraulic system with fresh, clean fluid. Make sure the fluid is of the correct type and is at the recommended level.
   
6. Check for Leaks: Once the system is refilled, check for leaks around the pump and other hydraulic components. Run the machine and monitor its performance to ensure the pump is functioning properly.
   

Preventive Maintenance for the Transmission Charge Pump
To avoid future charge pump failures in the International 520B, regular maintenance is essential:

1. Regularly Check Fluid Levels: Ensure that hydraulic fluid is always at the correct level. Low fluid can damage the charge pump and other components.
   
2. Change Hydraulic Fluid Periodically: Over time, hydraulic fluid can become contaminated with dirt and debris. Regularly changing the fluid helps prevent wear and ensures smooth operation.
   
3. Replace Filters: Hydraulic filters should be changed regularly to keep contaminants from entering the system. Clogged filters can cause pressure drops and pump damage.
   
4. Monitor Pump Performance: Keep an eye on the machine’s hydraulic performance. If you notice any decrease in efficiency, inspect the system for potential issues with the charge pump.
   
5. Avoid Overloading: Overloading the machine can put additional stress on the transmission and hydraulic system, leading to premature pump failure. Always operate the machine within its specified limits.
   

Conclusion
The International 520B is a reliable and powerful machine, but like all complex systems, it can experience issues such as transmission charge pump failure. By understanding the causes of pump failure, diagnosing the problem early, and performing regular maintenance, operators can extend the life of the equipment and minimize costly repairs. Ensuring the proper operation of the charge pump is essential for maintaining the efficiency and functionality of the loader, allowing it to perform effectively on the job site for years to come.