Troubleshooting a brake problem requires noticing the way the brake pedal reacts to being pressed and the way the vehicle behaves while the brakes are applied. A good way to test the brakes is to slowly drive around the block or to drive in an unpopulated area, such as a parking lot, while pressing and releasing the brakes and noting how they respond.
Brake problems often have simple solutions that can be diagnosed by symptoms associated with the pedal assembly, hydraulic brake lines, brake cables or brake rotor, and caliper assembly. One of the most dangerous brake malfunctions involves a defective master brake cylinder. Test the integrity of the master cylinder by pressing the brake pedal firmly to see if it sinks. A pedal that sinks to the floor rather than staying firm indicates the master cylinder is defective and unsafe.
Air in the brake lines can cause a spongy feeling in the pedal when applying the brakes. Bleed the brake lines, and refill the brake fluid reservoir if necessary to remedy the problem. When the brake fluid is often running low, this may indicate the vehicle's brake pads are worn or there is a leak in the brake lines. Other culprits frequently involved in brake fluid leakage are the wheel cylinders, brake calipers and master cylinder. A vehicle with a brake fluid leak shouldn't be driven until the leak is found and repaired.