How to Bleed Disc Brakes

How to Bleed Disc Brakes
Bleeding disk brakes is an important component to auto maintenance. The braking system uses hydraulic pressure to slow and stop the car's wheels when the brake pedal is depressed. Air infiltrating into the system will reduce this pressure and must be shed through bleeding. To properly bleed your vehicle's brakes, consult its specific repair manual and/or observe a professional mechanic do it. The following is simply a general overview of the manual method, which requires two people but little specialized equipment (as opposed to pressure bleeding), as laid out in Clifton E. Owen's "Classroom Manual for Automotive Brake Systems."
 

Instructions

Difficulty: Moderately Easy

Things You’ll Need:
  • Vacuum tubing
  • Clear container
  • Clean rag
  • Bleeder valve wrench
  • Assistant
 
Step 1
Ensure the master cylinder reservoir is full of brake fluid.
Step 2
Pump the brake pedal (engine off) about 10 times or until it firms up to rid the booster of vacuum.
Step 3
Attach a clear vacuum hose to the bleeder valve on the first wheel you're attending to after wiping away any residue. Submerge the other end of the hose in brake fluid in a clear jar.
Step 4
Open the bleeder valve one-quarter of a turn (with the appropriately-sized wrench).
Step 5
The assistant should depress the brake pedal with slow, consistent pressure. Fluid will begin exiting the submerged end of the hose and should initially contain air bubbles.
Step 6
Once the fluid is free of bubbles, close the valve and release the brake pedal. Repeat these steps until no air bubbles exit upon first opening the valve.
Step 7
Repeat the above steps for each wheel in accordance with the bleeding sequence recommended by the manufacturer. Replenish the master cylinder reservoir with clean brake fluid throughout and afterward to keep air out of the system.
Step 8
After all brakes have been bled and valves are closed, start the car and test the brake pedal for firmness (a spongy pedal indicates residual air in the system) and check the brake warning light for any issues. If there are, repeat the process until they're eliminated.
 

Resources

Article Written By Ethan Schowalter-Hay

Ethan Schowalter-Hay is a writer and naturalist living in Oregon. He has written for the "Observer," the Bureau of Land Management and various online publishers. He holds a Bachelor of Science in wildlife ecology and a graduate certificate in geographic information systems from the University of Wisconsin.

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