My brakes have started to make a loud moaning noise at slow speeds (crawling) when lightly applied. I don't hear it at higher speeds, when braking harder, or when reversing. I started hearing a little bit a few days ago but today was pretty loud. I was hoping it would go away. I only have 700 km on the car, and it's a TDI HL. I think it's coming from the rear. Any idea what it could be or if I need to take it in?