99 SL500, when I press the brake pedal I hear air hiss. It is not a constant hiss,only when I press the pedal when the pedal stops the hiss stops.
What do I need to replace ? Also,can not get shifter out of park unless push brake pedal very hard.
Thank you.

 

try having someone apply brakes while listening to brake vacuum booster under the hood behind the master cylinder. a stethoscope might help, a paper cup is better than nothin'. unusual for the diaphram to go bad. I've never had to deal with one.

 

I used a speed bleeder.
The (woosh) sound inside the car when brake is pressed is a new sound it never did that before.
When pressing on the brake pedal the shifter will not move out of park.