Most common questions used to investigate
Do the brakes make noise when you step on the brake pedal?
Brake noise can be caused by a number of factors, and all of them you need to take seriously. Do you hear a squealing noise when you step on the brakes?
Are the brake pedals low?
Does your brake pedal feel spongy or too soft?
Does your brake pedal sink into the floor?
Does the brake pedal pulsate when you step on it?
Are your brakes grabby? Do they suddenly slip and then grab, making your car suddenly jerk when you brake?
Are the brakes dragging?
Common conclusions
The brake pads might be a bit worn out and in need of replacement. The squealing noise is coming from the metal base of the brake pads scraping against the brake rotors.
If you are hearing a grinding noise, that is already pretty serious as the brake pads might be already so worn out and the metal base has ground up grooves into the brake rotor. You need to change all the brake pads wit brand new ones to prevent serious damage on your brakes. You might even need to have the rotors refaced.
If the default position of the brake pedal seems lower than normal, the shoe adjusters in the rear drum brakes might be covered in rust and are stuck in position. You just need to adjust the shoes and the brake will return to normal.
There might be air bubbles in the brake lines. To get rid of them, you need to bleed each brake line to push out the air from the lines. It is actually easy to bleed the brakes, but it will take two people to do this. If you do not have anyone who can help you bleed the brakes, it is best to have your mechanic do it for you.
If you step on your brake pedal and there seems to be no resistance and it just sinks into the floor. The master cylinder of the brakes is not holding enough pressure. If this happens while you are on the road, do not panic, just pump on the brakes a couple of times to get the master cylinder pressurized and it will work as normal for a short while. However, you need to bring your car immediately to the garage as you never know when your brakes would suddenly fail on you next time.
This might be caused by warped brake rotors. If this is the case, the brake rotor might need resurfacing, or if the warping is too serious, the entire rotor might need to be replaced.
The brake pads might be contaminated by grease, oil, or brake fluid. Aside from cleaning the brake pads, you need to find and fix the cause of the contamination. If the brake pads are covered with brake fluid, the calipers might have a small leak, so you need to get them fixed as soon as you can.
The usual suspects for dragging brakes are weak or broken retracting springs. You need to get this checked out because it can cause all sorts of other problems, like increased fuel consumption, excessive heating of the brake rotors and calipers, which might cause the brakes to weaken their grip.
References
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