Grinding noise from brakes, is it brake pads or rotors? (contains video)

Question

I recently got a used 2014 Hyundai Elantra GL (all 4 disc brakes) from a mechanic, he says the brake pads are new, but I continue hearing loud grinding noises from the front brakes (I suppose) from inside the cabin.

Here's a video I shot where you can clearly hear the noise.

https://photos.app.goo.gl/xAg6ww8osfgevZ7g9

The car also stops with a jerk.
In the video, you can see the camera shake because of this jerk.

What could be the problem here?

Answer 1

If by

he says the brake pads are new

you mean that the mechanic sold the car to you in road-worthy condition, then the brakes should:

1. Not be engaging when the pedal is not pressed;
2. Be evenly engaging when the pedal is pressed.

To test this:

1. Set the parking brake.
2. Jack up each of the front corners of the car using the jack that comes with it.
3. Spin each front wheel by hand. The wheel should turn reasonably freely and should not bind.
4. Have an assistant lightly press the brake pedal after you get the wheel spinning. The wheel should come to a stop evenly without binding or catching in any one spot.

If any of these tests aren't passing, the mechanic should repair the car's brakes. It could be the rotors are warped, the pads are not actually new, or that one or more calipers are binding.