Pulsing Brake Pedal on Volvo L90B Wheel Loader: Causes and Solutions

[MikePhua]

The Volvo L90B wheel loader is a versatile and reliable piece of heavy equipment used in a wide range of industries, from construction to material handling. Like all heavy machinery, the L90B is equipped with a braking system that ensures the operator can safely control the machine. However, one common issue that some operators face is a pulsing brake pedal, which can significantly affect the machine's performance and safety.
A pulsing brake pedal typically refers to the sensation of the brake pedal moving back and forth in a rhythmic pattern when the brake is applied. This can be a cause for concern, as it may indicate underlying issues with the braking system. In this article, we will delve into the potential causes of a pulsing brake pedal on the Volvo L90B, provide troubleshooting steps, and suggest solutions to rectify the issue.
Understanding the Volvo L90B Braking System
The Volvo L90B wheel loader, like many modern machines, uses a hydraulic braking system that ensures the vehicle can come to a controlled stop. This system relies on hydraulic fluid to transfer the force generated by the brake pedal to the braking components, such as the brake pads or shoes, which then apply pressure to the wheels. The system is designed to be efficient and responsive, providing operators with a smooth and predictable braking experience.
The Volvo L90B's hydraulic braking system also includes additional components such as:

• Brake Master Cylinder: Converts the force applied to the brake pedal into hydraulic pressure.
  
• Brake Calipers or Drums: Apply force to the wheels to stop the machine.
  
• Brake Lines and Hoses: Transport the hydraulic fluid throughout the system.
  
• Brake Fluid Reservoir: Stores and maintains the necessary fluid for the braking system.
  

What Causes a Pulsing Brake Pedal?
A pulsing brake pedal on the Volvo L90B can be caused by several factors, most of which are related to the hydraulic braking system. Below are some common causes of this issue:
1. Warped Brake Rotors or Drums
One of the most common causes of a pulsing brake pedal is warped brake rotors (or drums, depending on the system). Over time, brake rotors can become uneven due to excessive heat or wear. When the rotors are warped, the brake pads or shoes are unable to make consistent contact with the rotor surface, causing the brake pedal to pulse as the pressure fluctuates.
This issue is more pronounced when the brakes are applied at higher speeds or during heavy braking, as the difference in surface contact becomes more noticeable.
2. Air in the Brake Lines
Another potential cause for a pulsing brake pedal is air trapped in the brake lines. Air bubbles can compress and expand when the brake pedal is pressed, leading to inconsistent braking force and a pulsing sensation. Air in the brake lines is often caused by brake fluid leaks, improper maintenance, or air being introduced into the system during repairs.
3. Faulty Brake Master Cylinder
The brake master cylinder is responsible for generating the hydraulic pressure required to operate the brakes. If the master cylinder is malfunctioning, it may not be able to generate consistent pressure, which can lead to a pulsing brake pedal. This issue could be the result of a worn-out or damaged cylinder, as well as a loss of brake fluid.
4. Dirty or Contaminated Brake Fluid
Brake fluid plays a vital role in the hydraulic braking system, as it is responsible for transmitting force from the brake pedal to the braking components. If the brake fluid becomes contaminated with dirt, moisture, or air, it can affect the performance of the braking system and cause a pulsing brake pedal. Over time, old or contaminated brake fluid can lead to corrosion inside the brake lines or master cylinder, exacerbating the problem.
5. Worn Brake Pads or Shoes
Worn brake pads or shoes can cause uneven pressure on the brake system, leading to a pulsing sensation when the brakes are applied. If the brake pads or shoes are too thin or unevenly worn, they will not make consistent contact with the brake rotors or drums, resulting in a jerky or pulsing motion in the brake pedal.
How to Diagnose and Fix the Pulsing Brake Pedal Issue
If you are experiencing a pulsing brake pedal on your Volvo L90B wheel loader, follow these diagnostic steps to identify and resolve the problem:
1. Inspect the Brake Rotors or Drums
The first step in diagnosing a pulsing brake pedal is to inspect the brake rotors or drums. Look for signs of warping, scoring, or uneven wear. If the rotors are visibly warped, they will need to be replaced or resurfaced. In some cases, resurfacing the rotors may be enough to restore smooth braking, but if the damage is severe, replacement may be necessary.
2. Check for Air in the Brake Lines
If the rotors are in good condition, the next step is to check for air in the brake lines. This can be done by performing a brake bleed, which involves opening the bleeder valves on the brake calipers or drums to release any trapped air. Start with the wheel farthest from the master cylinder and work your way towards the closest wheel. If air is released during this process, you will need to top up the brake fluid and repeat the bleeding process until no more air bubbles are present.
3. Examine the Brake Master Cylinder
Next, inspect the brake master cylinder for signs of damage or fluid leaks. A malfunctioning master cylinder may need to be replaced to restore consistent hydraulic pressure. Check for any visible leaks around the cylinder or brake lines, and ensure that the fluid level is at the correct height. If the fluid is low, top it up with the recommended type of brake fluid.
4. Replace Contaminated Brake Fluid
If the brake fluid appears dirty, cloudy, or has a burnt smell, it is essential to replace it. Contaminated brake fluid can cause poor braking performance and lead to further damage to the hydraulic system. Drain the old fluid, flush the brake lines, and refill the system with fresh, clean brake fluid.
5. Inspect the Brake Pads or Shoes
Finally, check the condition of the brake pads or shoes. Worn or unevenly worn brake pads should be replaced to ensure smooth, consistent braking. Be sure to replace the pads with the correct type for your Volvo L90B and follow the manufacturer's guidelines for installation.
Conclusion
A pulsing brake pedal on the Volvo L90B wheel loader can be caused by various factors, including warped brake rotors, air in the brake lines, a faulty master cylinder, contaminated brake fluid, or worn brake pads. Proper diagnosis and timely repairs are essential to restoring the performance of the machine and ensuring operator safety. Regular maintenance, such as brake fluid checks, rotor inspections, and brake pad replacements, can help prevent this issue from occurring and extend the lifespan of your equipment.