HOWTO: Bleed the Brakes

Note: These are somewhat generic instructions and are based on the j-body platform. It's been brought to my attention that the Mazda3 uses a different order that doesn't keep with the logic of "furthest to closest". Be sure to check with instructions specific to your car before proceeding.

These instructions are based on having two people involved. There are single-person bleeding kits availble. To use such a system, please refer to the instructions that come with the kit.

A Note on Brake Fluid

The Internet is filled with misinformation and recently I've read some people suggesting that you use "DOT 3 or higher" fluid in your brake system.

This advice is WRONG.

For the most part, DOT 3 and DOT 4 fluids are compatable with one another though you should always read the labels.

DOT 5 fluid is NOT compatable with the others and is generally not compatable with most braking systems.

While DOT 5 fluid has a higher boiling point making it ideal for racing purposes, it requires a system designed for it. The fluid is silicon based, slightly compressible, and does not absorb water. DO NOT use this in a J-Body braking system!

I am currently running Valvoline SynPower DOT 4 fluid in my car.

Proper Bleeding Technique

• To avoid overflowing the reservoir in the future, bleeding should be done with fresh pads and shoes installed. If you're bleeding the system with worn pads or shoes, take note of the fluid level when you start and don't fill it higher than that during the bleeding procedure.
• Be very careful when working with brake fluid as it is extemely corrosive to paint. You do not want it touching any of the paint on the car under any circumstances.
• Slowly pour fluid into the master cylinder to avoid aerating the fluid.
• Take your time. Bleeding the brakes is not an exercise in seeing how far you can shoot the fluid from the bleeder valves.
• The instructions are applicable to most cars. In several places they refer to the corner farthest from the master cylinder. On the J-Body, this is the passenger side rear. It's been brought to my attention however that not all cars use this "furthest to closest" pattern of corners, so be sure to check instructions for your specific model before proceeding.

Dry System Preparation

Follow these steps only if the system is starting out with no fluid in it.

1. Fill the master cylinder with proper fluid.
2. At the corner furthest from the master cylinder, attach a clear plastic bleed line to the bleeder valve and open it.
3. Very slowly stroke the brake pedal by hand or foot until fluid comes out. Now close the bleeder.

Bleeding Sequence

When bleeding the system, you should always bleed the whole system even if you've only been working on one of the brakes.

1. Begin at the corner farthest from the master cylinder.
2. Not all cars require the wheels to be removed. If you can easily access the bleeder valve without removing them then you'll save yourself some work but remember that brake fluid is highly corrosive to paint so you may want to have those expensive wheels out of harm's way.
• Jack up the corner of the vehicle and secure with a sturdy jack stand.
• Remove the wheel.
3. Attach one end of the clear bleed tube to the bleeder valve. The other end should be hanging in a glass jar.
4. Have your partner slowly, with modest pressure, stroke the brake pedal one time until hydraulic resistance is encountered. Have him hold the pedal at this point and notify you when he is holding.
   • He should maintain the same pressure on the pedal, without moving it.
5. Open the bleeder, letting the pedal go to the floor or until it stops requiring the same modest amount of pressure to move.
6. Close the bleeder and notify your partnet that the system is sealed.
7. Repeat this sequence (never stroke the pedal more than one time) until all signs of air are purged (no bubbles) from the fluid.
   • IMPORTANT: Do not let the master cylinder run dry. Check the reservoir after every two or three strokes and refill as necessary.
   • Tap on the caliper or drum with a rubber mallet to dislodge any air that may be trapped within it.
8. When there are no more bubbles, close the bleeder and have your partner slowly press the pedal down and hold it at the floor while you ensure there is no fluid seeping out anywhere.
9. Fully clean the entire area to ensure no brake fluid has found its way outside of the jar. You don't want any splashing onto the vehicle when you start driving.
10. Move to the next farthest location from the master cylinder and repeat the above steps.