Breaks Grinding Noise

How many years approximately have the pads been on the car brake pad material does break down It does crack and can even fall out fall on the ground It's as hard as a rock heat to fix it time affects it especially also when your break accumulator and pump starts to fail and it gets in the latter stages it can hold calipers dragging I had this happen in my generation too right before the ABS pump and accumulator was totally shot and only one caliper would work at that point The left front but just before that all the brakes were working pretty much fine with the lights on but they would scrape in the front not a lot just enough to be irritating

 

Prius brakes (not breaks) are not used much due to regenerative braking so the rotors ten to rust. This will cause the brakes to make grinding noises. Periodically get your Prius up to 20-30 MPH, put it in neutral (turns off regenerative braking) and lightly apply the brakes to clean the rotor surfaces. Repeat this process a few times and the noise will go away.

JeffD