2006 xc70. I have had the car for several months. The brake pedal is no where as responsive as my 850 and S40. Here's the 'head scratcher': In the warmer weather, the pedal is quite mushy...feels like it is low and would go to the floor when depressing (it doesn't go to the floorboard- only feels that way). In the really cold weather (32 and below), the pedal is tight and high...'almost' like my other cars. I took it to Volvo, they want major cash just to diagnose. I would rather figure it out myself and do the repair at home. I figured I would start with a full bleed and fill...nice new DOT 4 fluid. If the booster were faulty, I gather that the pedal would be really difficult to depress...there are no hiss sounds. No fluid loss.
There,, that's all the info I can provide.