* Warped Rotors: This is the most common culprit. Over time, repeated braking, especially hard braking or overheating, can cause the rotors (the metal discs the brake pads grip) to warp slightly. This uneven surface creates the pulsating feeling in the pedal as the warped areas contact the pads.
* Scratched or Damaged Rotors: Deep scratches or scoring on the rotor surface can also cause pulsation, similar to warping.
* Rust on Rotors: Significant rust buildup on the rotors can create an uneven braking surface leading to pulsation.
* Sticking Caliper Piston(s): A caliper piston that's sticking or not retracting fully can cause uneven pressure on the brake pads, leading to pulsation. This often results in uneven pad wear as well.
* Seized Caliper: A completely seized caliper will lock the brake pad against the rotor, leading to a much more serious problem than just pulsation. This will likely be accompanied by other symptoms like pulling to one side while braking.
* Uneven Brake Pad Wear: While less likely to *cause* pulsation, extremely uneven brake pad wear can contribute to it if the worn pad allows the rotor to heat unevenly. This is often a *symptom* of a problem like a sticking caliper.
Troubleshooting and Repair:
To diagnose the issue, a mechanic will typically:
1. Inspect the rotors visually: Look for warping, scoring, rust, or damage.
2. Inspect the brake pads: Check for even wear.
3. Inspect the calipers: Check for sticking or seized pistons.
4. Check the brake lines and hoses: Look for leaks or damage.
The solution usually involves:
* Resurfacing or replacing the rotors: If the rotors are warped but not severely damaged, they can sometimes be resurfaced (machined to remove the warped areas). Otherwise, they need to be replaced.
* Replacing brake pads: Always replace pads when rotors are resurfaced or replaced to ensure even braking.
* Repairing or replacing calipers: Sticking or seized calipers need to be repaired (if possible) or replaced.
Ignoring a pulsating brake pedal is dangerous. Uneven braking can affect your ability to control the vehicle, especially in emergency situations. Get it checked out by a qualified mechanic as soon as possible.
