| Brake Pedal Hissing - Goes rock hard
Can someone please tell me what may be wrong with my car?
It started tonight, when i press my brake pedal there is a hissing, air being squeezed out noise. At first I thought it was the brake fluid being sprayed out, but the brakes are still working ok. I heard the noise over the road noise with the window open and the radio on.
I stopped the car (kept the engine running) and pumped the brake and the noise happened every time.
I then turned the engine off and pumped the brake again and the pedal went rock hard.
Reading on here it could be something to do with the servo valve i think, but can anyone give me a full description so i know what to say when i take it to the garage?
thanks | 
