When I release the brake pedal, I hear a squeak, and what sounds like a release of air. Has anyone experienced this before?
The vehicle is a 2002 S80 T6. 116K miles.
I had the timing belt done last year, the power steering pump, and the alternator. That's it.
This is a great car and I would recommend it to anyone. It's my second one.
Thanks for anyone's help.

 

I get the same issue. It's been doing it for a long time now and hasn't seemed to affect anything at all. I think it is the small pneumatic pump that controls the smoothness of the pedal.
The pneumo pumps on my trunk door do the same thing when I open it up all the way but there's no problems.

 

sometimes on mine I have a constant hissing coming from the brake pedel. sometimes i just have to give the pedal a little tap and it goes away, and sometimes it doesn't. It doesnt seem to effect the braking performance, but it does scary the hell out of my girlfriend. what could the cause of it be?

 

In all likelihood your brake booster is dying...
Its probably fine to use as it is, but eventually you will have to change it.. Its a common problem and there is a sticky..

On the other hand, mine has been behaving just like yours for about 3 yrs now and hasnt gotten any worse

 

I'm not too worried about it, but every now and then the pedel get really stiff. This typically only happens right after start up, once everything heats up it goes back to normal.

 

Sounds like bad brake booster to me. Eventually all brake assist will stop and the pedal will be hard at all times.

 

Had mine done in 2010...500 for part 700 labor...!!!!

 

yep - look here: https://volvoforums.com/forum/volvo-...ars-off-43983/

and here: https://volvoforums.com/forum/volvo-...lacement-6988/