How to Change Brake Fluid

You may need to remove the wheels to change brake fluid.

To change brake fluid you'll need to raise your car on jack stands or ramps, but beyond that, few supplies required. Purchase bottles of brake fluid in any auto parts store or major big box retailer in the motor oil section. Mechanics call the process "bleeding the brakes." You'll be suctioning out the old fluid and running clean fluid through the lines. Before you get started, find an assistant who can sit in the driver's seat and follow simple instructions.

Things You'll Need

• Jack stands or ramps
• Penetrating oil
• Box wrench
• Turkey baster
• Lint-free rag
• Aquarium tubing
• Brake fluid (2 or more 8-ounce cans)
• Clear bottle
• Small piece of 1-by-4 lumber
• Assistant

Instructions

1. Raise the car on jack stands or ramps. You may need to remove the wheels if you can't reach the brake bleeder valves, so keep this in mind when you raise your car.

2. Apply penetrating oil to the bleeder valve bolts, which are on each brake. Use your car's service manual to find the bolt if you don't see it. Popular Mechanics recommends applying the oil the day before you bleed the breaks to make the bolts easier to loosen.

3. Use a box wrench to gently loosen each bleeder valve bolt but do not open them yet. If the bolts are corroded, tap them to knock off loose corrosion and try again. You may need to change the calipers or wheel cylinders if corrosion causes the bolts to break off.

4. Suction out the old brake fluid from the master cylinder reservoir under the hood of the car. A turkey baster can be used to suction out a lot of fluid at once. Be careful not to get any brake fluid on painted surfaces; it will remove paint on contact.

5. Clean out the master cylinder reservoir with a lint-free rag. Be sure the rag is clean so no contaminants are introduced into the brake line.

6. Pour 1 or 2 inches of fresh brake fluid into a clear bottle and put it behind the right rear brake. Start with the right rear brake and work your way toward the front if you're doing all four wheels.

7. Attach a piece of aquarium tubing over the brake bleeder bolt on the right rear brake and put the other end into the clear bottle. Make sure the tube is submerged in the fresh brake fluid to prevent air from being sucked into the brake line.

8. Place a small piece of lumber under the brake pedal in the car so the pedal won't be pressed all the way down during the brake bleed.

9. Fill the master cylinder reservoir with fresh brake fluid. Replace the reservoir lid to prevent the fluid from spraying out when the brake pedal is released.

10. Ask your assistant to sit in the driver's seat to press the brake pedal while you open the bleeder bolt. Call out "down" to have the assistant press the brake pedal as if stopped at a light. The assistant should call out "down" when the pedal is down. That will be your signal to open the bleeder bolt a quarter turn to begin the bleed. The assistant must keep the brake pedal depressed, even if the pedal sinks to the lumber.

11. Watch the aquarium tube as old fluid drains through the line. When the fluid stops, close the bleeder bolt and call out "up" so your assistant can stop pressing on the brake pedal. Have your assistant call out "up" so you know he or she isn't pressing the brake line any more.

12. Repeat this sequence of "down" and "up" until clean brake fluid trickles through the line. It may take half a dozen or more cycles for each brake. Stop and refill the master cylinder reservoir every four to six cycles. Make sure the reservoir never drops below half empty or air may be sucked into the brake line.

13. Move the tube and bottle to the next brake and continue until all the brake lines have been bled.

Tips & Warnings

• Some cars with ABS require a specialized scan tool to cycle through the brake pumps and valves. Check the car's service manual and contact a mechanic or dealership to find the appropriate scan tool.

• Air in the brake system can cause damage to the system and "spongy" brakes. It's also very expensive to get air out of an antilock brake system (ABS), so be careful not to allow any air in. Popular Mechanics suggests the reservoir always remain at least half full while bleeding the lines.

References

• Popular Mechanics: How to Bleed Brakes
• Clark's Garage: Brake Fluid Changing