1. Worn or Damaged Brake Pads:
* Cause: This is the most common reason. Worn pads will create a scraping or scrubbing sound, especially noticeable at low speeds. Severely worn pads can also damage the rotors.
* Check: Visually inspect the brake pads through the caliper access holes (usually on the inside and outside of the wheel). Measure pad thickness with a caliper or use a visual guide comparing them to a new pad. Replace pads if they are worn below the minimum thickness (check your owner's manual).
2. Worn or Damaged Rotors:
* Cause: Worn or scored rotors create a grinding or scraping noise. Severe damage can cause pulsation in the brake pedal.
* Check: Visually inspect the rotors for scoring, grooves, or excessive rust. Use a dial indicator or straight edge to check for runout (wobble). If significantly worn or damaged, rotors need resurfacing (if possible) or replacement.
3. Caliper Issues:
* Cause: A sticking or seized caliper piston can cause the pads to constantly rub against the rotor. This usually results in a consistent scrubbing noise. A damaged caliper slide pin can also cause this.
* Check: Inspect the caliper pistons for free movement. Try pushing them back with a C-clamp or brake caliper tool. Lubricate the slide pins with high-temperature brake caliper grease (NEVER use regular grease). If the piston is seized or the pins are damaged, the caliper may need repair or replacement.
4. Brake Shield Interference:
* Cause: The brake dust shield (a thin metal plate behind the rotor) can sometimes bend or become loose, contacting the rotor and causing a scraping sound.
* Check: Visually inspect the brake shield for any contact with the rotor. Bend it back into place if necessary or replace it if damaged.
5. Wheel Bearing Issues:
* Cause: While less likely to sound exactly like brake scrubbing, a worn wheel bearing can sometimes produce a noise that might be mistaken for it, especially when braking. This noise is often more of a grinding or rumbling sound.
* Check: Jack up the car, support it securely, and grab the wheel at 3 and 9 o'clock and try to rock it back and forth. Excessive play indicates a worn bearing. Check for play in the wheel by attempting to move it up and down.
What to do:
1. Safety First: If you suspect a significant brake problem, avoid driving the car until it's addressed. Brake failure can be extremely dangerous.
2. Visual Inspection: Begin with a visual inspection of the brake components as described above.
3. Professional Help: If you're not comfortable performing these checks or repairs yourself, take your car to a qualified mechanic. Brake repair is critical for safety. They have the proper tools and expertise to diagnose and fix the problem.
Remember to always consult your owner's manual for specific information about your 2000 Pontiac Grand Prix's brake system.
