Ordinary brake fluid is hygroscopic, which means it readily absorbs any moisture found in the brake system. While this is important for preventing corrosion due to condensation in the system, brake fluid that is overly saturated with moisture will not perform effectively, causing excessive brake fade, mushy pedal feel and fluid vaporization due to a lowered boiling point. The best way to remove moisture from the brake system is to flush the old brake fluid from it. This task will require a partner, unless you have one-way bleeder valves installed or power bleeding equipment on hand.
Instructions
- 1
Loosen the lug nuts on the rear wheels with a lug wrench without removing them completely. Raise the rear of the vehicle with a floor jack and stabilize the vehicle with jack stands. Finish removing the lug nuts and remove the rear wheels.
2Determine how far the brake pedal goes down during normal operation and place a block of wood under the pedal to prevent it from going down any further. This will prevent damage to the brake system.
3Open the hood and locate the brake master cylinder reservoir. Clean the outside of the master cylinder reservoir with a shop rag to prevent dirt from getting inside. Remove the top covering the reservoir and remove as much brake fluid as possible with a turkey baster. Be careful not to spill brake fluid on painted surfaces. Fill the brake master cylinder reservoir with fresh brake fluid and close the reservoir.
4Start at the wheel that is furthest from the master cylinder. With many vehicles, it will be the passenger side rear wheel. Place a length of clear plastic tubing onto the bleeder valve and feed the tube into a clear container for collection. Place a box-end wrench on the bleeder bolt and prepare to open it.
5Instruct your partner to hold down the brake pedal. Open the bleeder valve with the box-end wrench and allow the old fluid to go through the tubing and into the container. Have your partner hold the brake pedal down until the fluid stops draining. Close the valve and instruct your partner to release the brake pedal.
6Open the master cylinder reservoir and top it up with fresh fluid. Do not let the fluid in the reservoir get too low, otherwise air will be sucked in through the master cylinder. Pump the brakes a few times then repeat the draining and refill procedure for each wheel, working from the wheel furthest from the master cylinder to the closest. This will remove both the brake fluid and moisture that was absorbed into the fluid from the brake system.
7Install the wheels on the car and lower it. Carefully test-drive the vehicle and check the brakes. If they feel mushy, air may have gotten into the system. You will need to bleed the brakes in order to remove all of the air from the system. Check the fluid levels in the reservoir and refill if necessary.
8Dispose the old brake fluid in an environmentally friendly manner. Many automotive parts outlets accept old fluid for proper disposal, free of charge.
