This master cylinder is a brand new product. The only failure mode that I know of for the master is that it will leak down and not hold a firm pedal. I was seeing this and now that it is replaced it will hold a very firm pedal. I don't think it is the mc.
What are the signs of a failed power booster? The one I have is a remanufactured one and was replaced about 2000 miles ago. My best guess would be that if the power booster weren't working well it would result in having to press very hard to get the brakes to be engaged??? Anyone know about this?
I'm going to get under the dash tomorrow and check out to see if I have a spring on the pedal. I'm betting I don't have one the way this thing will go down and stay down...I don't think I have bad bushings because the pedal moves freely otherwise. A spring to bring it back up would fix most of my issues except for the sensitivity which might just be due to the new master.