I noticed yesterday that my brakes felt a little low, then it went straight to the floor so I just figured one of my lines blew. I pulled over to check it out and not a single drop of fluid on the floor? Opened up the resevouir and it was full too... I'm starting to think its the master cylinder just going bad. I did notice that if I keep my foot on the brake pedal it will hold pressure but as soon as I let off even the slightest and push back in, it goes lower and lower until I have no brakes at all, then if I let go and wait a minute they work as long as i hold it steady and don't let off. Any ideas?
EDIT: I just did both front calipers and bled the system out correctly.