Do I need a brake fluid flush when I replace my brakes?
Brake fluid, like other fluids used in our vehicles, is subject to degradation over time. Brake fluid is a hydraulic and hygroscopic substance which means it absorbs moisture if left exposed to atmospheric humidity. Minute pieces of rubber can break down from inside the lines and the master cylinder and also contaminate the fluid. We need to consider the heat that the fluid is exposed to during the braking process. If water has gotten absorbed into the fluid, it can turn the fluid slightly acidic.
As a preventative maintenance and to extend and improve the braking function of your vehicle it is recommended that the fluid be replaced or flushed every few years in your system. The best time for consistent change is actually when you have your brakes changed. The brake system is a sealed system where pressure is applied from the driver through the brake pedal to the master cylinder and lines and then to the end of the brake system, which is at either the wheel cylinders or the calipers depending on your type of brake system setup. Gravity helps to send the worn rubber particles or debris to the end of the line during this process. Since a sealed hydraulic system allows the action on the pedal at one end to actuate the brakes at the other end, if the brakes are replaced, the pistons are merely compressed and they will actually send the dirt and debris back toward the master cylinder. Most of today's vehicles have complicated ABS systems which contain solenoids that perform the action of pulsing the brakes to allow for a more controlled stop while allowing for steering control as well. If the caliper pistons are simply retracted to make room for the new brake pads, the fluid will push under pressure back through the system and can damage these sensitive parts. Similar to changing oil and coolant periodically, changing your brake fluid on a regular basis will help to prevent problems while maximizing the heat and braking force to allow for safer stopping.
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