Komatsu PC120-6 Low Pressure Issues: Causes and Solutions

[MikePhua]

The Komatsu PC120-6 is a widely used hydraulic excavator known for its robustness and versatility. However, like any heavy equipment, it can experience performance issues over time. One such issue that many operators face is low hydraulic pressure, which can affect the machine’s lifting capacity, digging performance, and overall efficiency. Understanding the causes of low hydraulic pressure in the PC120-6 and knowing how to address them is crucial for maintaining optimal machine performance.
Understanding the Hydraulic System in the PC120-6
Before delving into the causes of low hydraulic pressure, it's essential to understand how the hydraulic system works in the Komatsu PC120-6. The hydraulic system is responsible for powering various functions of the excavator, including the boom, arm, bucket, and rotation. The system operates using hydraulic fluid, which is pressurized by the hydraulic pump to transmit power to the hydraulic cylinders.
The hydraulic pump in the PC120-6 draws fluid from the hydraulic reservoir and pumps it into the system under high pressure. This pressurized fluid then drives the hydraulic motors and cylinders, allowing the excavator to perform its tasks. If there is an issue with hydraulic pressure, the performance of these functions can be severely compromised.
Common Causes of Low Hydraulic Pressure
There are several reasons why the hydraulic pressure in a Komatsu PC120-6 might drop below the optimal level. These can range from mechanical failures to issues with fluid quality or system components. Here are the most common causes of low hydraulic pressure:

1. Hydraulic Fluid Contamination
   • Hydraulic fluid contamination is one of the most common causes of low hydraulic pressure. Contaminants like dirt, water, or metal shavings can enter the system and cause blockages or damage to critical components such as the pump, valves, and filters.
     
   • Symptoms: If the hydraulic fluid appears milky, cloudy, or dirty, it could indicate contamination.
     
   • Solution: Drain the contaminated fluid and replace it with fresh hydraulic oil that meets the manufacturer’s specifications. Ensure that the hydraulic filters are replaced and check the system for any leaks or damage that might allow contaminants to enter.
     
2. Low Hydraulic Fluid Levels
   • If the hydraulic fluid level is too low, the pump will not be able to draw enough fluid to generate proper pressure. This can result in the system operating at a reduced capacity or even failure.
     
   • Symptoms: The hydraulic functions may become sluggish, and you may hear the pump cavitating or whining.
     
   • Solution: Check the hydraulic fluid level regularly and top up if necessary. If the fluid is consistently low, inspect the system for leaks in hoses, seals, or the reservoir.
     
3. Faulty Hydraulic Pump
   • The hydraulic pump is the heart of the hydraulic system, responsible for generating the necessary pressure. A worn-out or malfunctioning pump can cause low pressure, reducing the effectiveness of the hydraulic system.
     
   • Symptoms: Slow or weak response from hydraulic functions, increased engine load, or hydraulic warning lights.
     
   • Solution: Inspect the hydraulic pump for signs of wear, leakage, or damage. If the pump is faulty, it may need to be rebuilt or replaced.
     
4. Damaged or Worn Hydraulic Valves
   • Hydraulic valves control the flow of fluid to various components of the excavator. If these valves become clogged, damaged, or worn, they can restrict fluid flow and lead to low pressure in the system.
     
   • Symptoms: Unresponsive or jerky hydraulic movements, uneven lifting, or issues with specific hydraulic functions.
     
   • Solution: Inspect and clean the valves, and replace any that are worn or damaged. A valve bypass could be the issue if fluid is not flowing as it should.
     
5. Clogged Hydraulic Filters
   • The hydraulic filters are designed to prevent contaminants from entering the hydraulic system. Over time, filters can become clogged with debris, restricting fluid flow and causing a drop in pressure.
     
   • Symptoms: Slow or erratic hydraulic performance, overheating of the hydraulic fluid, or an illuminated filter warning light.
     
   • Solution: Replace the hydraulic filters according to the maintenance schedule, or more frequently if operating in harsh conditions. Ensure that the filter housing is also cleaned when changing the filters.
     
6. Leaking Seals or Hoses
   • Leaks in the hydraulic system, whether from worn seals, cracked hoses, or loose connections, can result in a loss of pressure. Even small leaks can cause a significant drop in pressure over time.
     
   • Symptoms: Visible fluid leaks, puddles around the excavator, or sudden drops in pressure during operation.
     
   • Solution: Inspect all hydraulic hoses, fittings, and seals for signs of wear, cracking, or leaks. Replace any damaged components and ensure all connections are tight and properly sealed.
     
7. Overheated Hydraulic System
   • Excessive heat can cause the hydraulic fluid to thin out, reducing its ability to create the necessary pressure. Overheating can also damage seals and other components, leading to low pressure.
     
   • Symptoms: Hydraulic fluid temperature readings that exceed the normal operating range, poor performance, or engine overheating.
     
   • Solution: Check the cooling system and ensure the radiator is clean and functioning correctly. Maintain the recommended fluid temperature and avoid overloading the machine to reduce heat buildup.
     
8. Incorrect Pressure Settings
   • The hydraulic system in the PC120-6 is set to operate within a specific pressure range. If the pressure relief valve or the pump pressure is set too low, it can result in low hydraulic pressure.
     
   • Symptoms: Decreased lifting or digging performance, or sudden drops in hydraulic pressure during operation.
     
   • Solution: Use a hydraulic pressure gauge to check the system’s pressure. Adjust the pressure relief valve settings to match the manufacturer’s specifications. If the pressure regulator is faulty, it may need to be replaced.
     

How to Troubleshoot Low Hydraulic Pressure in the Komatsu PC120-6
If you are experiencing low hydraulic pressure on your Komatsu PC120-6, follow these steps to diagnose and fix the issue:

1. Check the Fluid Level and Quality
   • Start by checking the hydraulic fluid level and ensuring that the fluid is clean and free of contaminants. If the fluid appears dirty or discolored, replace it and change the filters.
     
2. Inspect the Pump
   • If the fluid is in good condition, inspect the hydraulic pump for signs of damage or wear. Check the pump’s pressure output with a gauge to ensure it’s operating within the manufacturer’s specified range.
     
3. Examine the Hydraulic Hoses and Seals
   • Look for any leaks in the system, including cracked hoses, damaged seals, or loose fittings. Replace any faulty components and tighten all connections.
     
4. Test the Valves and Filters
   • Inspect the hydraulic valves for any blockages or damage. Check and replace any clogged filters. Ensure that the valves are properly adjusted and functioning.
     
5. Check for Overheating
   • Ensure that the hydraulic system is not overheating. If it is, inspect the cooling system, clean the radiator, and ensure proper airflow.
     
6. Perform a Pressure Test
   • Use a pressure gauge to check the system's hydraulic pressure. If the pressure is too low, adjust the pressure relief valve or replace the pump if necessary.
     

Preventative Maintenance for the Komatsu PC120-6
To avoid low hydraulic pressure issues in the future, it’s important to follow a strict preventative maintenance schedule. Regular maintenance will ensure that the hydraulic system remains in optimal condition, preventing costly repairs down the line. Here are some key maintenance tips:

1. Regularly Check Fluid Levels: Always monitor the hydraulic fluid levels and top up as necessary. Make sure that the fluid is clean and free of contaminants.
   
2. Change Filters on Schedule: Follow the manufacturer’s recommended schedule for replacing hydraulic filters to prevent clogging and contamination.
   
3. Inspect Hoses and Seals: Routinely check hydraulic hoses, seals, and fittings for signs of wear or damage. Replace any components that show signs of degradation.
   
4. Flush the System: Periodically flush the hydraulic system to remove debris and prevent buildup that could cause blockages.
   
5. Monitor Pressure Settings: Ensure that the hydraulic pressure is set to the correct specifications for your operating conditions. Adjust the pressure relief valve as necessary.
   

Conclusion
Low hydraulic pressure in the Komatsu PC120-6 can significantly affect the machine’s performance and productivity. By understanding the common causes of low pressure, performing regular inspections, and addressing issues promptly, you can ensure that the hydraulic system remains efficient and reliable. Following a comprehensive maintenance schedule and using the right diagnostic tools will help you troubleshoot and resolve low hydraulic pressure problems, allowing you to keep your Komatsu PC120-6 running at peak performance for years to come.