Hi, Friday my car decided to make a new noise, when I depress the brake pedal (while the car is idling) I hear a whistling sound which is about 1.5 second long, i only hear it when I depress the brake pedal from the original position, when I'm already braking and press it harder I hear nothing. When the car is off the pedal goes hard after about 3 cycles and stays hard, not going down to the floor. When I start the car with my foot on the brake it is sucked it, so in theory the servo is ok. But I did notice that the brake goes 'hard' after the car has been parked for about 5 minutes


I know the servo is vacuum filled and that some air enters the servo from the other side of the booster, most likely the inside of the car when the booster is bolted to the bulkhead. My q's are:

1) Should I start worrying or is this sound normal?
2) If not, where do I start, is there a filter and sound damper that can be replaced etc?



BTW, on RHD cars the master cylinder's end moves about 3 mm up when the pedal is depressed, I would have thought that the bulkhead would have been strengthened to prevent it but I was wrong.