My car has started making a noise when I brake. It only does it when I have done about 30 miles or more and it sounds like a whirring sound. It doesn't do it when I change gear to stop just if I brake. It's an intermittent fault, it will do it if I stop using the car, then get back in it and the engine hasn't cooled but won't do it if the engines cold. It's not the brake discs or pads because I've had them checked. The garage can't diagnose it because it's intermittent and doesn't do it when it's there. I do a lot of miles and the car is on newly 80,000 now.
