Bleeding Meritor Full Pressure Hydraulic Brakes: A Step-by-Step Guide

[MikePhua]

Introduction to Meritor Full Pressure Hydraulic Brakes
Meritor full pressure hydraulic brakes are commonly found in heavy-duty trucks and equipment. These brakes rely on hydraulic pressure to apply force to the braking system, ensuring effective stopping power. Like any hydraulic brake system, maintaining the proper pressure and ensuring air is not trapped in the brake lines is crucial for safe operation. One of the most common maintenance tasks required for hydraulic brakes is "bleeding" the system, which involves removing air that has entered the brake lines. This article will guide you through the steps of bleeding Meritor full pressure hydraulic brakes to ensure your braking system works optimally.
Why Bleed Hydraulic Brakes?

1. Importance of Proper Brake Performance
   • Air in the brake lines can lead to a "spongy" or unresponsive brake pedal, reducing the overall braking effectiveness. If air is not removed, it may cause delayed or weak braking, potentially leading to dangerous situations.
     
   • Bleeding the hydraulic brake system ensures that the braking power is fully restored, as it removes air bubbles that might have entered during maintenance or as a result of a brake fluid leak.
     
2. When to Bleed the Brakes
   • You should bleed the hydraulic brakes whenever you notice a soft or spongy brake pedal, especially if you recently had work done on the brake system.
     
   • Other signs that bleeding is necessary include a loss of brake fluid or if you replace any part of the braking system, such as brake lines, cylinders, or master cylinders.
     

Tools and Materials Needed
Before you begin bleeding the brakes, gather the following tools and materials:

1. Brake Fluid: Use the manufacturer-recommended brake fluid for your Meritor hydraulic braking system.
   
2. Brake Bleeder Kit: A brake bleeder kit typically includes a hose, jar, and valve to help safely capture the brake fluid while you bleed the system.
   
3. Wrench: A suitable wrench to open and close the bleeder valve.
   
4. Rag: To clean up any spills or excess brake fluid.
   
5. Helper: You may need an assistant to press the brake pedal while you open and close the bleeder valve.
   

Step-by-Step Process for Bleeding Meritor Full Pressure Hydraulic Brakes

1. Prepare the Vehicle
   • Park the vehicle on a flat, level surface to prevent any unintended movement.
     
   • Ensure the engine is off and the parking brake is engaged.
     
   • If the vehicle has been in use, allow it to cool down before working on the brakes.
     
2. Locate the Brake Bleeder Valves
   • The bleeder valves are located on each brake assembly. These valves allow the brake fluid to escape and any trapped air to be released.
     
   • Identify the bleeder valve on each wheel cylinder or caliper.
     
3. Check the Brake Fluid Level
   • Before starting the bleeding process, check the brake fluid reservoir. Ensure that the fluid is at the recommended level. Low brake fluid levels can cause air to enter the system, so top off the fluid if necessary.
     
   • It’s also important to use the correct type of brake fluid specified for the Meritor hydraulic system.
     
4. Attach the Bleeder Kit
   • Attach the hose from the brake bleeder kit to the bleeder valve on the first wheel.
     
   • Place the other end of the hose into a container to catch the expelled fluid.
     
   • You can also place a rag around the valve to catch any fluid that may spill out during the process.
     
5. Start Bleeding the Brakes
   • Have your assistant pump the brake pedal a few times and hold it down (keeping pressure on the pedal).
     
   • While the pedal is held down, use the wrench to open the bleeder valve. This will allow brake fluid to flow out along with any trapped air.
     
   • Once fluid starts to flow freely, close the bleeder valve. Then, instruct your assistant to release the brake pedal.
     
   • Repeat this process of pumping, holding, opening the valve, and closing it until no air bubbles are visible in the fluid. The fluid should flow smoothly without interruption.
     
   • It’s important to keep an eye on the brake fluid level in the reservoir throughout the process to avoid introducing more air into the system by letting the level drop too low.
     
6. Repeat for All Brakes
   • After completing the bleeding process on the first wheel, move on to the next wheel and repeat the process.
     
   • Typically, it is recommended to start with the wheel farthest from the master cylinder (usually the passenger side rear) and work your way towards the closest (driver’s side front). This ensures the best results for air removal.
     
7. Check for Proper Pedal Feel
   • After completing the bleeding process on all wheels, have your assistant press the brake pedal to check for firmness.
     
   • The pedal should feel firm and responsive. If it still feels soft or spongy, repeat the bleeding process to ensure all air has been removed from the system.
     
8. Top Off the Brake Fluid
   • After completing the bleeding process, check the brake fluid level once more. Add brake fluid if necessary to bring it back to the correct level.
     
   • Clean up any spilled brake fluid, as it can damage paint or other vehicle components.
     

Final Inspection

1. Test the Brakes
   • Before driving, test the brake function by gently applying the brakes while the vehicle is stationary.
     
   • If the brake pedal feels firm and the vehicle stops as expected, you have successfully bled the brakes.
     
2. Inspect for Leaks
   • After the bleeding process, inspect all the connections, including the bleeder valve and any hoses, for signs of leaks.
     
   • If you find a leak, fix the issue immediately before operating the vehicle.
     
3. Test Drive
   • Once you’re confident the brakes are functioning correctly, take the vehicle for a short test drive to ensure the brakes are fully operational.
     

Conclusion: Ensuring Safe and Effective Braking
Bleeding the brakes on a vehicle with Meritor full pressure hydraulic brakes is an essential maintenance task that ensures safe and efficient braking performance. By following the proper steps and ensuring that all air is removed from the system, you can maintain the optimal functionality of your braking system. Regular brake maintenance not only ensures the safety of the driver but also extends the life of the hydraulic brake components, preventing costly repairs down the road.