Description
If you have bled your brakes but still have a soft pedal, your master cylinder may be the problem. With the car running, press the brake pedal. If your pedal does not maintain a constant feel, then it is most likely the master cylinder.
The Master Cylinder converts pressure applied to the brake pedal into hydraulic force that is transmitted to the brake calipers and wheel cylinders. Internal brake master cylinder leaks reduce hydraulic pressure at the wheels, resulting in partial or total loss of braking.