Understanding and Maintaining Brakes on the 920 Wheel Loader: A Comprehensive Guide

[MikePhua]

The braking system of a wheel loader is a crucial component that ensures the safe operation of the machine. On the 920 wheel loader, as with any other heavy equipment, brakes are responsible for stopping or slowing down the machine, preventing accidents and ensuring smooth control, especially when operating under heavy load conditions. This article will explore the essential aspects of the braking system in the 920 wheel loader, common problems encountered with the brakes, maintenance practices, and troubleshooting techniques.
Overview of the Braking System in the 920 Wheel Loader
The 920 wheel loader, like many other loaders, is equipped with a hydraulic braking system. This system uses fluid pressure to transfer force from the brake pedal to the brake components, allowing for efficient stopping and smooth operation.
Key components of the braking system in the 920 wheel loader include:

1. Brake Pedal: The primary interface for the operator to engage the braking system.
   
2. Brake Master Cylinder: This component converts the force from the brake pedal into hydraulic pressure that is sent to the brake cylinders.
   
3. Brake Cylinders: These are responsible for applying pressure to the brake pads or shoes, causing them to clamp down on the brake discs or drums.
   
4. Brake Pads and Shoes: These friction components create the necessary resistance to slow down the wheel loader’s motion.
   
5. Brake Discs or Drums: The rotating components that the brake pads or shoes press against to slow the wheel loader down.
   
6. Hydraulic Lines and Fluid: The hydraulic system relies on fluid to transfer pressure from the master cylinder to the brake cylinders. The fluid must be in good condition for optimal braking performance.
   

In addition to these core components, the 920 wheel loader’s braking system may feature auxiliary systems such as parking brakes and retarder systems, which provide additional control when the machine is not in motion or needs to decelerate quickly.
Common Brake Problems in the 920 Wheel Loader
Braking problems in the 920 wheel loader can manifest in various ways. Below are some common issues that operators may encounter with the brake system, along with their possible causes.
1. Brake Fade
Cause: Brake fade occurs when the braking system becomes less effective due to overheating. This typically happens after prolonged or heavy braking, where the friction material (pads or shoes) becomes too hot to provide adequate stopping power.
Signs:

• Reduced braking effectiveness
  
• Longer stopping distances
  
• The brake pedal feeling softer or spongy
  

Solution:

• Ensure proper cooling time between heavy braking sessions.
  
• Check for proper brake fluid levels and ensure there is no air in the hydraulic system.
  
• Inspect the brake pads or shoes for excessive wear and replace them if necessary.
  
• If brake fade is a frequent issue, it may indicate that the braking system is undersized or improperly calibrated for the loader’s load capacity.
  

2. Brake Fluid Leaks
Cause: Leaks in the brake hydraulic system can result from damaged seals, worn hoses, or cracked brake lines. Leaking brake fluid reduces the hydraulic pressure required to engage the brakes, leading to reduced braking performance.
Signs:

• Brake pedal feels soft or spongy
  
• Reduced braking power
  
• Visible fluid leakage around brake components
  

Solution:

• Inspect all hydraulic lines, hoses, and seals for leaks or cracks.
  
• Replace damaged hoses and seals.
  
• Refill the brake fluid to the proper level and bleed the brakes to remove any air from the system.
  

3. Worn Brake Pads or Shoes
Cause: Over time, the friction material on the brake pads or shoes wears down due to repeated contact with the brake discs or drums. Worn pads or shoes can significantly reduce braking efficiency.
Signs:

• Grinding or squealing noise when applying the brakes
  
• Increased stopping distance
  
• Vibration in the brake pedal or steering column
  

Solution:

• Inspect the brake pads and shoes regularly for wear. If the friction material is thin or worn down, replace them with new ones.
  
• Check the brake discs or drums for scoring or damage, as worn-out pads or shoes can damage these components.
  

4. Contaminated Brake Fluid
Cause: Contaminants such as dirt, moisture, or air bubbles can enter the brake fluid, which reduces its effectiveness and can cause corrosion of internal brake components.
Signs:

• Reduced braking response
  
• Brake fluid discoloration (it may appear darker or murky)
  
• Presence of moisture or bubbles in the brake lines
  

Solution:

• Regularly inspect brake fluid for contamination. If the fluid appears dirty or discolored, it may need to be replaced.
  
• Drain and replace the contaminated brake fluid with fresh, manufacturer-recommended fluid.
  
• Flush the entire brake system to remove moisture or dirt.
  

5. Uneven Brake Wear
Cause: Uneven wear on the brake pads or shoes can occur due to misalignment of the brake components, improper installation, or a failure of the brake calipers or cylinders.
Signs:

• One side of the loader pulls to one side when braking
  
• Uneven braking response or noise
  
• Excessive wear on one or more brake pads/shoes
  

Solution:

• Inspect the brake calipers and cylinders for proper alignment and movement.
  
• Replace damaged or worn components to ensure even wear across all brake pads or shoes.
  
• Ensure that the brake components are installed correctly, following the manufacturer’s instructions.
  

Brake Maintenance for the 920 Wheel Loader
Proper maintenance of the braking system is essential to ensure safe and efficient operation of the 920 wheel loader. Here are some key maintenance practices that can prolong the life of the brakes and prevent issues from arising:
1. Regular Brake Inspections

• Inspect the brake pads and shoes at regular intervals to check for wear.
  
• Look for signs of leaks, corrosion, or damage in the hydraulic lines and components.
  
• Check the brake fluid level and ensure it is within the recommended range.
  

2. Brake Fluid Replacement
Brake fluid should be replaced at regular intervals as specified by the manufacturer. Over time, brake fluid can absorb moisture, which can lead to reduced braking performance and the possibility of brake fade.

• Flush the brake system periodically to remove old fluid and contaminants.
  
• Always use the recommended brake fluid type to ensure compatibility with the system.
  

3. Bleeding the Brakes
If air has entered the brake system due to leaks or during fluid replacement, it can cause the brakes to feel soft or spongy. Bleeding the brakes removes the air from the hydraulic lines.

• Use a brake bleeder kit to purge the air from the brake lines.
  
• Ensure that the brake fluid is topped up after bleeding.
  

4. Check Brake Components for Wear

• Regularly inspect the brake discs or drums for wear, scoring, or cracks. If they are damaged, replace them promptly.
  
• Ensure the brake calipers and cylinders are functioning correctly and are not seizing or sticking.
  

5. Proper Use of the Brakes

• Avoid excessive or prolonged braking, which can lead to overheating and brake fade. Instead, allow the loader to slow down gradually whenever possible.
  
• If the loader is used for heavy or continuous operation, ensure that the brakes are properly rated for the load and work conditions.
  

Case Study: Resolving Brake Fade on a 920 Wheel Loader
A construction company operating a Volvo 920 wheel loader on a busy construction site faced frequent issues with brake fade during long-haul operations. Despite regular maintenance and brake inspections, the operator noticed that the loader’s brakes would become ineffective after several heavy stops.
Upon closer inspection, it was discovered that the brake fluid was contaminated with moisture, causing the fluid to lose its ability to absorb heat effectively. The solution was to flush the entire hydraulic brake system, replace the brake fluid, and ensure that all seals and hoses were intact. After the service, the loader’s braking performance returned to normal, and the brake fade issue was resolved.
Conclusion
The braking system of the Volvo 920 wheel loader is essential for safe and efficient operation. Regular inspection, maintenance, and prompt repairs are crucial to keep the system functioning properly. By addressing common issues such as brake fade, fluid leaks, worn brake pads, and contaminated fluid, operators can ensure that their wheel loader remains safe, reliable, and capable of handling the toughest jobs on the worksite.