One of the symptoms that indicate a brake fluid flush is needed is a spongy or soft brake pedal. If the pedal feels less responsive or sinks to the floor, it may be due to air or moisture in the brake lines.

Ideally, brake fluid flushes should be done every two to three years or as recommended by the vehicle manufacturer. However, certain driving conditions, such as heavy towing or frequent stop-and-go traffic, may require more frequent flushes. It is important to consult the owner's manual or a trusted mechanic to determine the appropriate interval for a specific vehicle.

The process of doing a brake fluid flush involves draining the old fluid from the brake lines and replacing it with fresh, clean fluid. This is typically done by bleeding the brakes, which involves opening the bleeder valves on each brake caliper or wheel cylinder and allowing the old fluid to flow out. The process is repeated until the fluid runs clear and free of contaminants.