Bleed Car Brakes
Do you need to bleed the brakes of a car to refresh them? Have you gotten your brake pads replaced recently, but notice a spongy feel when you engage the brakes? Sometimes, when the brake fluid level drops too low in the master cylinder reservoir, air bubbles can get caught in the lines, reducing the overall strength of the brake fluid column. Getting the air out of the brake fluid column will restore the full strength of the hydraulic brakes.
Steps
- Remove the top of the master cylinder reservoir. It is usually a light colored reservoir with a black cap and is usually is inline with your brake pedal in the engine compartment.
- Draw out the old fluid. Using a clean turkey baster, suck out as much of the old, inky fluid as you can.
- Clean the reservoir. After you've gotten all the old brake fluid out, clean any sediment out of the reservoir, if accessible, with a clean, lint-free rag. Do not spill any brake fluid on any painted surfaces, it will remove the paint almost immediately. Clean up any spilled fluid with a brake clean fluid or soap and water.
- Fill the master cylinder with clean brake fluid. Replace the top of the master cylinder reservoir.
- Pump the brake pedal several times (15 or more).
- Loosen the bleeder valves. Using a box-end wrench (often 5/16") that fits the bleeder bolt, loosen the bleeder valves, but leave them closed. A little oil drizzled or sprayed on the bolts the day before will help to loosen them.
- Hook a tube to the bleeder bolt. Using a piece of clear plastic tubing (aquarium tubing works fine), push one end of the tube over the brake bleeder bolt.
- Put the other end of the tube into a small, clear bottle with an inch or two of clean brake fluid in it. (This will keep air from being sucked back into the brake cylinder or lines.)
- Put a piece of 1 x 4 lumber or some other "spacer" under the brake pedal. This will prevent the pedal from traveling too close to the floor and you begin to bleed the brakes. This is needed so you do not bottom out pistons in the master cylinder and causing internal master cylinder leakage.
- Refill the master cylinder reservoir. Remove the top of the master cylinder reservoir and top off the master cylinder reservoir with fresh fluid. Keep the master cylinder full during process otherwise air might get into system.
- Replace the top of the master cylinder reservoir.
- Have a helper sit in the driver's seat and slowly depress the brake pedal with an even force and hold it down. The helper should shout "down" when the pedal is down as far as it will go.
- Note: Not too much force is needed. Press down as much as you would to fully come to a halt before a stop sign.
- Starting with the rear passenger wheel (back right for left-hand drive cars), turn the bleeder bolt to the left one quarter-turn. Old fluid and air will go down the tubing into the bottle. When the fluid stops, close the bleeder valve.
- Note: Warn your helper that the brake pedal he or she is pressing down on will sink down as you unlock the bleeder bolt a quarter turn. This is perfectly natural and your helper should keep pressure and follow pedal down until it stops and hold it down.
- Shout "up" to your helper, who at this point should remove his or her foot from the pedal, allowing it to move up.
- Repeat this process until new, clear fluid comes from the bleeder tube. After every five times the brake pedal is depressed, top off the master cylinder reservoir with fresh fluid. Never let the reservoir get too low, or air will be sucked into the master cylinder.
- Tighten the bleeder bolt back up.
- Repeat steps 12 to 15 on the left rear wheel.
- Repeat steps 12 to 15 on the right front wheel.
- Repeat steps 12 to 15 on the left front wheel.
- Finished. Your brakes have been properly bled. Thank your helper by buying him or her a beer or cream soda. Never take your help for granted.
- Never use brake fluid not fit for a specific car
Tips
- For ABS antilock brake systems) type brakes, you may need to use a special scan tool during the bleeding process to cycle the pump and valves. Do not attempt to bleed your brakes if your vehicle has ABS brakes or traction control without the specialized scan tool to activate these systems during the bleeding process.
- Stores like Autozone sell cheap (under $5) plastic and catcher brake (not break) bleeder kits, which are a big help.
- Some later model vehicles call for a special bleed procedure known as a "Bleeding Sequence" due to the various valves and systems used. Consult a professional first before attempting to bleed as problems and/or damage to your brake system can happen if improperly bled.
- Bleeder bolts can become difficult to remove. Use a proper-fitting box wrench to keep from rounding them off.
- Apply a small hose on the end of the bleed tap. Submerge the end of the hose in a bottle filled with brake fluid. Loosen the tap. Pump the brake pedal making sure you keep the master cylinder full.
- If you don't know what you are doing, get a professional to assist you. Improper bleeding can cause air to get into the system and cause the brakes to not work properly.
- Always start from the furthest of the master brake cylinder. Usually, it's back right to back left, then front right to front left.
- Doing this alone is NOT RECOMMENDED, air can be sucked in around the threads of the bleeder valve! If a pressure bleeder is used, then bleeding can be done by one person.
Warnings
- Brake fluid is nasty stuff. You will want to keep it out of your eyes and off your driveway. If possible, use a hose and jar to catch it as it squirts out and then recycle it.
- Always use the manufacturer's recommended brake fluid for your car. Using the wrong fluid (like engine oil) can result in brake failure, which is a very bad thing. If you survive the brake failure you will then have to replace some fairly expensive parts.
- Brake fluid will destroy the paint on your car! Take care not to spill it on paint!
Things You'll Need
- Box wrench.
- Clear plastic tubing.
- 2 8 oz. cans of Brake Fluid.
- Turkey baster.
- Clear plastic bottle.
- Spacer (ie. A piece of 1x4 lumber)
- Another person to be your helper.
- Scan tool for ABS or Traction control
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