what would cause the brakes on a 2007 impala to feel as though they are catching and releasing constantly while coming down a mountain on the interstate in NC? The Chevrolet dealer put their computer on my vehicle and could not find a problem.

Most likely warped brake rotors.


Please clarify if you were applying the brakes when you felt this “on again, off again” situation with your brakes.

If you were applying your brakes when you had this problem, then I agree that it is likely to be warped brake rotors. On the other hand, if you were not applying your brakes at the time, then…I am drawing a blank.

I am voting for rotors, but don’t rule out ABS based on the limited data from the OP. That might explain the "dealer put their computer on my vehicle and … "

Hooking up a computer to a car will not give any insight into a brake performance issue, as the braking system is not tied into the OBD system.

I agree that the culprit is most likely warped brake rotors.
Do you feel that pulsing vibration any other time while driving your car?

Also, you shouldn’t use your brakes to slow a vehicle while going down a long steep grade. You should shift the transmission into a lower gear, and let the engine braking do the work.

This is to prevent the brakes from being overheated, and warping, which could lead to brake failure under extreme circumstances.