Troubleshooting Hydraulic Issues in the Poclain 75 CKB (1983 Model)

[MikePhua]

The Poclain 75 CKB, a tracked excavator manufactured in the 1980s, is widely recognized for its robust hydraulic system that powers the digging arm, bucket, and other attachments. However, like any heavy machinery, the Poclain 75 CKB is susceptible to hydraulic issues that can lead to reduced performance or complete system failure. When the hydraulics fail to operate, it can be a significant problem, often affecting productivity. This article explores the causes and solutions for hydraulic issues in the Poclain 75 CKB (1983 model) and provides insights into troubleshooting and repairing these problems.
1. Overview of the Poclain 75 CKB Excavator
The Poclain 75 CKB is part of Poclain’s CKB series of tracked excavators, known for their high efficiency in various excavation tasks, such as digging, lifting, and material handling.
Key features include:

• Engine power: Approximately 75 horsepower
  
• Operating weight: Around 16 tons (14,500 kg)
  
• Hydraulic system: A closed-center, load-sensing hydraulic system designed for precise control
  
• Bucket capacity: Typically between 0.5 to 1 cubic meter, depending on configuration
  

The hydraulic system in the Poclain 75 CKB is essential for all major movements and functions, including the operation of the boom, arm, and bucket. When this system malfunctions, it’s crucial to diagnose the problem as quickly as possible to minimize downtime and repair costs.
2. Understanding the Hydraulic System in the Poclain 75 CKB
The hydraulic system in the Poclain 75 CKB is designed to operate under high pressure and is responsible for driving key components of the excavator. The system includes:

• Hydraulic pump: The heart of the system, converting mechanical energy from the engine into hydraulic energy to power the various functions of the machine.
  
• Hydraulic cylinders: Used in the boom, arm, and bucket to create the necessary force for lifting and digging.
  
• Control valves: Direct the flow of hydraulic fluid to different parts of the machine based on operator input.
  
• Hydraulic fluid: The medium that transfers the energy, usually oil-based, which must be maintained at proper levels and cleanliness for the system to work efficiently.
  

When any part of this system fails, the machine’s hydraulic functions may stop working, leading to issues like slow response, unresponsiveness, or a complete hydraulic failure.
3. Common Causes of Hydraulic Failures
Several factors can contribute to hydraulic system issues in the Poclain 75 CKB. Understanding these causes can help in troubleshooting and determining the necessary repairs.
3.1 Low Hydraulic Fluid Levels
One of the most common causes of hydraulic failure is low hydraulic fluid. The hydraulic system relies on a sufficient amount of fluid to function correctly. Low fluid levels can result in the system losing pressure, leading to weak or nonfunctional hydraulics. This issue could be caused by:

• Leaks in hydraulic hoses or fittings: Small cracks or loose connections can cause gradual fluid loss.
  
• Improper fluid maintenance: Not topping off fluid regularly can lead to a slow depletion over time.
  

3.2 Clogged Hydraulic Filters
Hydraulic systems rely on clean fluid to avoid damage to components such as pumps and valves. If the fluid becomes contaminated with dirt, metal particles, or debris, it can clog the filters, restrict fluid flow, and ultimately lead to system failure. This is a particularly common issue in older models like the 1983 Poclain 75 CKB.
3.3 Faulty Hydraulic Pump
The hydraulic pump is crucial in providing pressure to the system. If the pump fails, the entire hydraulic system will cease to function. The pump can fail due to internal wear, contamination, or issues with the drive shaft.
Signs of a failing hydraulic pump include:

• Loss of pressure: The pump may fail to generate the necessary pressure to power the hydraulic functions.
  
• Unusual noise: A worn-out or damaged pump may produce grinding, whining, or screeching sounds.
  
• Reduced flow: The hydraulic cylinders may move slower than usual or not at all.
  

3.4 Leaking Seals
Seals within the hydraulic cylinders, pump, or control valves can wear over time and fail to keep the hydraulic fluid in place. This can result in leaks, leading to a drop in fluid levels and pressure. Leaking seals are a common issue in older machines like the Poclain 75 CKB.
3.5 Malfunctioning Control Valves
Control valves direct the hydraulic fluid to the appropriate cylinders based on the operator’s inputs. If these valves fail, the fluid may not reach the correct components, causing some parts of the machine to remain unresponsive. Common issues with control valves include sticking, wear, and internal damage.
3.6 Air in the Hydraulic System
Air trapped in the hydraulic system can cause erratic or unresponsive behavior. This may occur due to:

• Improper fluid filling: If the hydraulic fluid is added too quickly or with improper techniques, air bubbles may be trapped inside.
  
• Leaks: Air can enter the system through loose fittings or damaged seals.
  

3.7 Damaged Hydraulic Lines
Over time, hydraulic lines can become damaged due to abrasion, corrosion, or accidental impact. If a hydraulic line breaks or is punctured, it will result in a loss of hydraulic fluid and failure of the system.
4. Troubleshooting Hydraulic Problems in the Poclain 75 CKB
When faced with a hydraulic failure on the Poclain 75 CKB, it’s important to follow a systematic troubleshooting approach.
4.1 Check Hydraulic Fluid Levels and Condition
Start by checking the hydraulic fluid levels. If the levels are low, inspect the system for leaks, and top off the fluid with the appropriate type. Also, examine the condition of the fluid; if it appears dark or contaminated, it may need to be replaced.
4.2 Inspect Hydraulic Filters
Inspect and clean the hydraulic filters to ensure there are no clogs. If the filters are excessively dirty or damaged, they should be replaced.
4.3 Check for Leaks
Examine all hydraulic lines, hoses, and seals for signs of leaks. Pay particular attention to the connections near the hydraulic pump, control valves, and cylinders. If leaks are detected, replace the damaged components immediately.
4.4 Test the Hydraulic Pump
If fluid levels are adequate and there are no visible leaks, the next step is to test the hydraulic pump. This may involve checking for unusual noise or pressure loss, both of which are signs of pump failure. A diagnostic tool can also be used to measure the pump’s output pressure.
4.5 Inspect Control Valves
If the pump seems to be functioning correctly, inspect the control valves for any blockages or malfunctioning components. Test the responsiveness of the valves by moving the control lever and observing if the hydraulic components respond as expected.
4.6 Check for Air in the System
If air is suspected in the system, bleed the hydraulic lines to remove any trapped air. This can be done by opening the bleeder valves on each hydraulic cylinder and allowing the air to escape while the pump is running.
5. Solutions to Hydraulic Problems
Once the issue has been identified, the following solutions can help restore the hydraulic system’s functionality:
5.1 Add or Replace Hydraulic Fluid
If low fluid is the cause, top off the system with the correct hydraulic fluid. If the fluid is contaminated, perform a complete fluid change and replace the filters.
5.2 Replace Clogged Filters
Dirty or clogged filters should be replaced to ensure clean fluid flows through the system.
5.3 Repair or Replace the Hydraulic Pump
If the pump is damaged, it may need to be repaired or replaced. Replacing the pump can be expensive, but it’s necessary for restoring full hydraulic functionality.
5.4 Fix Leaks and Replace Seals
Leaks should be repaired as soon as possible. Replace any worn-out seals, hoses, or fittings to prevent further fluid loss and pressure drop.
5.5 Replace Malfunctioning Control Valves
Faulty control valves should be replaced to restore proper fluid distribution throughout the system.
5.6 Bleed the System
If air is present in the system, ensure all air is bled out and that the hydraulic fluid is free of contaminants.
6. Preventive Maintenance for Hydraulic Systems
To reduce the likelihood of future hydraulic issues, regular maintenance is essential:

• Monitor fluid levels: Regularly check and maintain the appropriate hydraulic fluid levels.
  
• Change fluid and filters: Perform routine fluid and filter changes according to the manufacturer’s recommendations.
  
• Inspect hoses and seals: Check for wear and replace any damaged components.
  
• Check for leaks: Routinely inspect the system for leaks, especially after heavy use.
  
• Maintain the pump: Keep the pump clean and well-lubricated to ensure smooth operation.
  

7. Conclusion
Hydraulic issues in the Poclain 75 CKB, especially with the 1983 model, can be caused by various factors, including low fluid levels, clogged filters, faulty pumps, and leaking seals. By following a systematic troubleshooting process and addressing the root cause, operators can restore hydraulic functionality and ensure optimal performance. Regular maintenance is key to prolonging the life of the hydraulic system and preventing future problems.