Stange question. I have a 2001 V70XC, there is a squeak or whistle that comes from the brake peadal when it is released. It also sounds like a rush or release of air coming from the same area. It only happens when the pedal is released and not all the time, mainly when the car is warm. If Iput pressure on the brake pedal it will stop the squeak. It has recently gotten much louder also. I have looked under there and it appears to be a filter with a rubber boot that moves in and out. Any suggestions?????

 

Brake booster is bad.

 

Thank you. Is it expensive??

 

Sorry but yes it is.
The part itself is I believe like $300.00 or more alone. (Not exactly sure about prices I really only install the parts)

 

Thanks.

 

Second the brake booster. I had the same symptoms on my 02 VW Jetta (I know, totally different car) but it was a bad power brake booster.