Nissan Repair: patfinder 2005, brake pads and rotors, vacuum booster

Question
Twice now, I went to pull out of my driveway and it felt like I had no brakes.  It was very hard to press on the brake pedal.  i pulled over both times and had to pump the pedal and no longer had the problem. Both times it was cold out. I recently had the front brake pads and rotors changed on 11/09.  Why would this happen?  Thank you in advance for your help.. Pat

Answer
Pat,

Sounds like the vacuum booster for the master cylinder is leaking off after it is parked.  There is a check valvbe that could be defective or the vacuum booster itself could be torn and leaking inside.  You could try to start the engine and let it run a few minutes to build up vacuum and see if the problem goes away after you drive it.  If this is the case have the check valve and vacuum booster checked to see which one it is.  If it were your master cylinder the pedal would go to the floor and after you pump the brakes the pedal would come back to its original position.  But, since you say it is hard and the brakes are not working well I say it is the booster or the check valve.