Hissing from the brake pedals being push indicates that there is air in the brake system. It also indicates that the brake pads may be wore down and are not able to grab to stop the car.
bad master cylinder
it is hissing because there is a vacume leak in the brake booster it will require a new brake booster
air coming out of the brake lines... that is if its a truck. if you aply the parking brake.
Faulty Vacuum Brake Booster.
By the hissing noise it sounds like you need a new brake booster
The power brake booster may be going bad.
Yes, if pushed out far enough the piston will come out.
Excessive or heavy and continuous braking may warp brake rotors. Braking hard (heating the rotors a lot) and then going through water (which quickly cools the hot rotors) may also cause the rotors to warp. If the brake pads or brake rotors are getting thin, the rotors will warp more easily.
Your brake booster is malfunctioning
worn thin
my sister pushed me off the couch.
a switch that is trigered to light up the light when the brake pad is pushed in