Understanding and Resolving Hydraulic Noise in the Kubota SVL Series

[MikePhua]

Hydraulic systems are essential for the performance of skid steer loaders like the Kubota SVL series. They power crucial functions, from lifting and digging to turning and pushing. However, a common issue that owners of these machines face is unusual hydraulic noise, which can change with the engine RPM. This kind of noise is often concerning because it suggests that something within the hydraulic system is not functioning as it should.
In this article, we will delve into the possible causes of this hydraulic noise in Kubota SVL skid steers, the factors influencing it, and the steps to troubleshoot and resolve the issue. We will also discuss some preventive maintenance tips to help you keep your machine running smoothly.
What Causes Hydraulic Noise in the Kubota SVL Series?
Hydraulic noise in skid steer loaders is a frequent concern and can arise due to various issues within the hydraulic system. These noises typically manifest as whining, grinding, or humming sounds that become more pronounced as the engine RPM increases. Here are some common causes:
1. Low Hydraulic Fluid Levels
One of the most common causes of unusual hydraulic noise is low hydraulic fluid levels. If the fluid level falls below the recommended amount, the pump may start drawing in air, which causes cavitation. Cavitation creates bubbles within the hydraulic fluid, and when these bubbles collapse, they generate a distinct "grinding" noise.

• Solution: Always check your hydraulic fluid levels regularly. If the fluid is low, top it off with the manufacturer-recommended hydraulic fluid. If you notice a significant drop in fluid levels over time, inspect the system for leaks and address them promptly.
  

2. Air in the Hydraulic System
Air trapped in the hydraulic system can lead to a similar effect as low fluid levels, causing the pump to struggle. As the hydraulic fluid is forced through the system, the air pockets disrupt normal flow, leading to inconsistent pressure and the characteristic noise. This issue can also cause sluggish performance in the loader’s hydraulic functions.

• Solution: Bleed the system to remove any air. Many Kubota SVL models have a designated procedure for this, so refer to the user manual for step-by-step instructions. Regular maintenance and fluid changes can help minimize the risk of air entering the system.
  

3. Worn or Faulty Hydraulic Pump
A hydraulic pump is at the heart of the system, responsible for pressurizing the hydraulic fluid. If the pump begins to wear out, it may struggle to produce the required pressure, leading to noise that correlates with engine RPM. As the pump's internal components degrade, the efficiency decreases, and the noise level can increase significantly.

• Solution: Inspect the hydraulic pump for signs of wear or damage. If the pump is producing excessive noise or is showing signs of reduced performance, it may need to be rebuilt or replaced. Regular maintenance, including fluid changes and system flushes, can extend the life of the pump.
  

4. Contaminated Hydraulic Fluid
Contaminants such as dirt, metal shavings, or moisture in the hydraulic fluid can lead to improper lubrication of critical components, resulting in excess friction. This friction can generate noise, and over time, it can cause significant damage to pumps, valves, and other hydraulic components.

• Solution: If you suspect that the hydraulic fluid is contaminated, it’s essential to flush the system and replace the fluid. Also, consider installing or replacing the hydraulic filters to prevent further contamination. The fluid should be replaced at intervals recommended by Kubota to ensure the longevity of your hydraulic system.
  

5. Incorrect Hydraulic Fluid Viscosity
Hydraulic systems are designed to operate with fluids of a specific viscosity, or thickness. If the hydraulic fluid is too thick or too thin for the conditions, it can create increased friction within the pump and the system. This can lead to noise that fluctuates with engine RPM. For example, fluid that is too thick may not flow efficiently at higher RPMs, causing a whining noise as the pump struggles.

• Solution: Always use the recommended hydraulic fluid for your specific Kubota SVL model, taking into account the environmental conditions. In colder climates, you may need to use a fluid with a lower viscosity to ensure smooth operation.
  

6. Faulty Hydraulic Valves or Relief Valves
The hydraulic valves control the flow of hydraulic fluid to different parts of the loader, and if these valves are malfunctioning, it can lead to inconsistent pressure. Relief valves are especially important in regulating system pressure. If a relief valve is stuck or malfunctioning, it may fail to regulate the pressure properly, causing erratic fluid flow and resulting in noise.

• Solution: Inspect the hydraulic valves and relief valves for any signs of failure or malfunction. If necessary, replace or repair faulty valves to restore proper hydraulic function.
  

Step-by-Step Diagnostic Process for Hydraulic Noise
If you're experiencing hydraulic noise in your Kubota SVL, follow this diagnostic process to pinpoint the cause:
1. Check Hydraulic Fluid Levels

• Start by checking the hydraulic fluid levels. Low fluid levels can often be the simplest cause of noise.
  
• Inspect the fluid for contamination. If the fluid is dirty or has a burnt smell, replace it.
  

2. Inspect for Air in the System

• Look for bubbles or foam in the fluid reservoir. If air is present, it could be due to a loose or damaged hose, or a failure in the system seals.
  
• Bleed the hydraulic system to remove any trapped air and restore fluid flow.
  

3. Listen for Changes in Noise

• Note when the noise changes with RPM. If the noise intensifies as the engine speed increases, this could indicate a problem with the hydraulic pump or fluid viscosity.
  
• A grinding noise that correlates with higher RPMs could signal cavitation or pump wear.
  

4. Check the Hydraulic Pump

• Inspect the pump for any signs of wear or damage. A failing pump may produce a distinctive whine or grind.
  
• Test the pressure output using a pressure gauge. Low pressure could indicate a pump problem.
  

5. Inspect Hydraulic Filters

• Inspect the hydraulic filters for blockages or damage. A clogged filter can lead to increased system strain, causing noise and poor performance.
  
• Replace filters if necessary and ensure that the system is properly flushed.
  

6. Check Hydraulic Valves

• Inspect the hydraulic valves for any signs of malfunction. A faulty valve could be causing pressure irregularities in the system, leading to noise.
  

Preventive Maintenance to Avoid Hydraulic Noise
Preventing hydraulic noise and potential system failure is largely about regular maintenance. Here are some tips to help you keep your Kubota SVL hydraulic system in top shape:

• Regular Fluid Checks: Check hydraulic fluid levels and condition regularly. Replace the fluid at intervals recommended by Kubota, typically every 1,000 to 1,500 hours of operation, or when the fluid shows signs of contamination.
  
• Filter Replacement: Replace the hydraulic filters regularly, as they can become clogged with debris, which can reduce system efficiency.
  
• Monitor Fluid Temperature: Keep an eye on the temperature of the hydraulic fluid. Excessive heat can cause fluid breakdown, which leads to increased friction and wear on components.
  
• Inspect Hydraulic Lines: Regularly inspect hydraulic hoses, fittings, and seals for leaks or damage. Even small leaks can lead to loss of pressure and performance, contributing to noise.
  
• Listen for Unusual Sounds: Pay attention to any changes in sound while operating the machine. Early detection of abnormal sounds can help you catch issues before they turn into costly repairs.
  

Real-World Example: Resolving Hydraulic Noise in an SVL Skid Steer
A Kubota SVL75-2 owner experienced fluctuating hydraulic noise that seemed to worsen as engine RPMs increased. After performing a thorough inspection, the owner found that the hydraulic fluid was both low and contaminated with debris from a recent job site. By replacing the fluid and installing new filters, the noise decreased significantly, and the machine’s performance returned to normal.
This case highlights the importance of regular maintenance and prompt action when hydraulic noise is noticed. It also emphasizes how simple issues like fluid contamination or low fluid levels can lead to bigger problems if not addressed quickly.
Conclusion
Hydraulic noise in Kubota SVL skid steer loaders is a common issue that can stem from various causes, including low fluid levels, air in the system, worn pumps, or contaminated hydraulic fluid. Identifying the source of the noise involves a systematic diagnostic process, starting with fluid checks and moving through more complex system inspections. Regular maintenance is key to preventing hydraulic noise, ensuring the longevity of the hydraulic system, and maintaining overall machine performance.
By addressing issues promptly and following proper maintenance schedules, owners can keep their Kubota SVL series machines running smoothly and efficiently, avoiding costly repairs and minimizing downtime.