Brake pedal is pulsating

Disc brakes offer improved stopping power and performance over older style drum brakes. They can be equipped with an ABS system as well, which helps to prevent your wheels from locking up under hard braking, or braking in wet driving conditions. However, if you feel the brake pedal pulsating when you press it, there may be something wrong with your brakes.

How this system works:

Both disc and drum brakes work on the basis of friction. When the caliper squeezes the rotor between the brake pads, it creates friction. This is what slows down and stops your car. It also produces heat.

If your rotors overheat, you’ll find that that high spots are created on the surface. They can also be warped – the most common way is by overheating the rotors and then driving through a puddle, which immediately cools and warps them.

Both high spots and warping cause brake pads to skip and grab as they move over the surface of the rotor. This is translated through the pedal as pulsations. There’s also the possibility that you’re experiencing pulsation from the ABS system. If you notice the pulsation only on hard stop and during wet driving, chances are that it’s normal ABS operation. You should not experience it during normal braking on a dry road, though.

Common reasons for this to happen:

  • High Spots on Rotors: If high spots have formed on your rotors, you’ll experience a pulsating brake pedal. You may also experience abnormal brake pad and rotor wear. The only way to eliminate this problem is to have the rotors resurfaced. If the rotors are worn already, you may need to replace them.
  • Warped Rotors: If your rotors have been warped, this will also create a pulsating brake pedal. Warped rotors can sometimes be resurfaced, but if the warping is severe, replacement might be the only option.
  • Normal ABS Operation: If you’re experiencing a pulsating brake pedal only occasionally, and only during “panic” stops or in wet driving conditions, chances are good that it’s normal ABS operation. A brake inspection service should tell you if there’s a problem.
  • Thinning Brake Fluid: Like engine oil and transmission fluid, your brake fluid must be replaced periodically. As it ages, the fluid “thins” and can sometimes absorb moisture, which reduces performance and can lead to a pulsating brake pedal. The rough estimate is every two years, but heavy braking may require more frequent changes.

How it’s done:

The mechanic will need to inspect the entire brake system. While warped rotors and unevenly worn rotors are generally the primary cause here, there are other concerns. The mechanic may need to remove the wheels to inspect the pads and rotors as well.