Troubleshooting a Pulsating Brake Pedal When Applying Brakes

Pulsing brakes are a direct result of the rapid shifting of the brake assembly against the braking surface. The rotor or drum brake surface must be flat to enable smooth braking. Braking surfaces that have significant variation due to warping, damage, uneven wear or misalignment cause the brakes to unevenly be applied. As the brake pads contact the high spots, the brakes grab slightly. When the brake pads leave the high spots, the braking strength is reduced. As the wheel turns rapidly, the brake pads have uneven pressure between the high and low spots, causing pulsation.

Instructions

1

Park the vehicle and place wheel chocks around the wheels not being inspected. Loosen the lug nuts on the wheels with the pulsing brakes. Jack the vehicle to raise the wheel above the pavement and place jack stands under the vehicle. Remove the lug nuts and wheel from the lug posts.

2

Inspect the brake pads in the calipers, if the brakes are disk brake design. If less pad exists than metal backing, the pads should be replaced. If the leading edge of one pad is significantly worn while the trailing edge of the pad on the opposite side is worn, the rotor or calipers are out of alignment. Typical causes are poor connection of the wheel to the hub, debris caught between the wheel and hub or rotor and hub, or misaligned calipers. In all cases, the rotor should be resurfaced, if possible, or replaced. Replace brake pads with significant or uneven wear.

3

Spray a penetrating lubricant around the lug posts and hub to loosen any corrosion holding the drum in place, if you are inspecting drum brakes. Remove any retaining screws securing the drum to the hub. Slide the drum off the hub and inspect the brake shoes for uneven wear or obvious signs of damage. If the drum brakes are throbbing, as with disk brakes, resurface or replacement of the drums and shoes are necessary.

4

Rotate the rotor or axle. Watch and listen for contact from the rotor against the brake pads. The brakes should rotate freely. Have an assistant lightly press the brakes to close the distance between the pad and rotor. Properly functioning braking systems should have full contact or no contact. Intermittent contact indicates the rotor surface is either warped from excessive heat or has high and low spots due to uneven wear. Rotors or drums with warping or uneven wear should be resurfaced or replaced.

5

Clean the inside wheel well and mounting surface with a wire brush to free any trapped debris that may cause misalignment when the wheel is installed.

6

When replacing the wheel, use a torque wrench to ensure all lug nuts are evenly tightened according to manufacturer specification. A single loose lug nut can cause uneven pressure on the braking system, causing the brakes to wear unevenly and pulsate.

7

Perform, or have a professional perform, a four-wheel alignment. Misalignment may cause pulsing if the surfaces have been worn down unevenly.