Problem with 2007 Chevy cobalt brakes.
When the car is cold and at lower speeds, applying the brakes are smooth and does not pulse.
After driving the car and warming up the brakes, when applying the brakes at highway speeds, I am hearing and feeling the ABS system is pulsing. The harder the brakes are applied, the louder the noise and feel of the pulsing. All four wheels had been serviced six months ago, new front rotors and pads, and new shoes for the back. The pulsing doesn’t feel like warped rotors. The noise is like an impact wrench. The braking is smooth and controlled. Is this normal?

 

The ABS sensors on the front wheels need cleaning or replacing.

 

to be sure this is not a base brake problem; pull the abs fuse to disable the abs pump. test drive; if the noise is still present, its not abs related.