2002 BMW 330i Q&A

2002 BMW 330i Question: my bmw 2002 330i has a hissing sound when pressing the brakes and when it's idle

what needs to be fixed and what"s the cost? -
Answer 1
sounds like you have a vacuum leak or a brake booster is your pedal hard when you brake? -
Answer 2
Brake booster Dont know the cost -