My Rav4 Hybrid has been making brake grinding noises since new. The noise is a short buzzy grind when coming to a stop, which ends up sounding like a fart. At first, I thought it was new brakes bedding in or something, it was a brand new car. With 18k miles, it has quieted down a slight bit but still does it. Stopping on a downslope exacerbates the problem. Mentioned it to Toyota on normal service and I believe they tried to say it was normal. I've seen TSB for this brake noise and it may actually be a problem with the brake master cylinder.