how to bleed a drum brake

How to Bleed a Drum Brake

Bleeding a drum brake is an essential maintenance task that ensures the braking system functions effectively. Over time, moisture and air can enter the brake lines, leading to reduced braking performance and possibly unsafe driving conditions. This article will guide you through the process of bleeding a drum brake accurately and safely.

Understanding the Components

Before diving into the bleeding process, it’s important to understand the components of a drum brake system. A typical drum brake setup includes brake shoes, a brake drum, a wheel cylinder, and brake lines. When you press the brake pedal, hydraulic fluid is pushed through the lines to the wheel cylinder, which expands the brake shoes against the drum to create friction and slow down the vehicle.

Tools Required

To begin bleeding your drum brakes, you’ll need the following tools and materials

1. Brake fluid – Ensure you use the correct type (e.g., DOT 3, DOT 4). 2. Wrenches – A line wrench is preferable for this task. 3. Bleeding kit – Optional but helpful; it allows for easier collection of brake fluid and prevents air from re-entering the system. 4. Rags and a container – For fluid spillage and waste fluid collection. 5. A helper – An extra pair of hands can make the process smoother.

Safety First

Before starting, ensure you are working in a well-ventilated area. Wear safety glasses and gloves to protect yourself from brake fluid, which can damage paint and irritate skin. Make sure the vehicle is on a stable surface, and the parking brake is engaged.

Step-by-Step Bleeding Process

1. Locate the Bleeder Screw Find the brake bleeder screw on the wheel cylinder of the drum brake you plan to bleed. It is typically a small, metal screw.

2. Remove the Wheel If necessary, raise the vehicle using a jack and remove the wheel to access the brake drum and cylinder.

3. Fill the Reservoir Check the brake fluid reservoir under the hood of your vehicle. Fill it with new brake fluid to the recommended level to prevent introducing air into the system during the bleeding process.

4. Attach the Hose If you are using a bleeding kit, attach the clear hose to the bleeder screw and place the other end into a container to catch the old brake fluid. If not, have your helper ready to catch the fluid as it comes out.

5. Open the Bleeder Screw Using the appropriate wrench, slowly open the bleeder screw about a quarter to half a turn.

6. Pump the Brake Pedal Have your helper press the brake pedal several times and then hold it down to build pressure. Once they have pressed the pedal down, instruct them to keep it pressed.

7. Close the Bleeder Screw While your helper's foot is still on the brake pedal, tighten the bleeder screw. This action prevents air from being drawn back in.

8. Release the Brake Pedal After closing the bleeder screw, your helper can now release the brake pedal.

9. Repeat the Process Repeat the open-pump-close procedure until you see a steady stream of clear brake fluid without air bubbles. This may take several cycles, so be patient.

10. Check Fluid Levels Throughout this process, make sure to monitor the brake fluid level in the reservoir, as it may decrease significantly. Top off if needed.

11. Reinstall the Wheel and Lower the Vehicle Once you have completed the bleeding process, make sure to snugly tighten the wheel and lower the vehicle back to the ground.

Final Steps

After bleeding all the brakes as needed, pump the brake pedal to ensure it feels firm. A soft pedal indicates that there might still be air in the system, requiring further bleeding. Always dispose of any used brake fluid properly, as it is hazardous to the environment.

Conclusion

Bleeding drum brakes is a vital maintenance skill for any vehicle owner. By following these steps, you can enhance your brake performance and ensure safer driving. If you're ever in doubt or uncomfortable, don’t hesitate to consult a professional mechanic for assistance. Remember, your safety is paramount.