Flushing is just that, flushing the old
dirty fluid out of the system and replacing it with new clean fluid
The symptoms of a car that needs to flush brake fluid:
Braking feels mushy
Slow response when braking
High milage between flushing
Brake fluid
absorbs water from the atmosphere, lowering its boiling point and
causing corrosion, particulate contamination, microscopic particles of
rust and rubber accelerating the wear of very expensive brake
components. This is why you should fully flush your brake system every
year, but never more then every two years. In addition, whenever the
hydraulic system has been opened like when a component is replaced, the
system must be bled of air.