suspected servo problem

[billewizz]

done all the checks in the book and i get the hiss and all that but when you start the engine and get some vacume, brake pedal goes down so strong that it puts the brakes on have i got a dead servo

[Paul]

turn car off, pump brake pedal til it goes hard, when it goes hard, keeping foot on pedal, turn the car on, if pedal doesnt drop the servo is in technical terms fooked.