im not to sure whatsgoin on but i drove my car to ther wreckers today and get a part and when i left to drive out onto the high way i realised that the brakes barely worked. its as if the brake booster isnt workin. the pedal is hard as a rock and it has barely any braking power. there is also a hissing sound comin form under the dash in the drivers side foot well. i have recently done some work on the car but i have drivin it since and havent had any preoblems until now all of a sudden the brakes dont work. i have checked the hose to the booster and it appears to be fine.

any suggestions as to what could be trhe problem??

diaphragm inside booster has perished from age and is leaking - need to replace brake booster.

but doesnt it seem a little strange to happen all of a sudden. i have had other cars older than this one and never expericed this before