bigava@comcast.net

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?

bigava@comcast.net

FYI, I have found the solution to this issue. I did pull the fuses for the ABS system, and performed a second test drive. I thought that it had improved the braking, so went looking for wheel sensors. Finding only one sensor, on the passenger side in the transaxle, none at the rotors, and none on the driver side of the transaxle. Next, I went to the Chevy dealer and spoke to a service manager about my issues. With going into a lot of time, he said to check the rotors thickness and run out. . Went home, pulled out dial indicator and check the run out. Found that both sides of the rotor(s) had only less than .001 inch run out. Did not have a mic with points, only flats. Put it back together, and drove it again. This time with the fuses pulled from the ABS, this time there was no difference between fuses in or out. Pulled the rotors and had them turned. Put it back together and test drove it again.
Problem gone, problem solved. There was only a little less then .001 of an inch thickness in the rotor and the same in the run out.