What could cause the brake master cylinder to go bad 4 times in 6 years? Basically the very first stock OEM Motorcraft Master Cylinder lasted 3 years before it went out. It went out by the pedal always going to the floor and making a loud pop noise from behind the pedal even though brakes would be bled and fluid changed air always continuously would get in the lines. After the first 3 years of owning the 2008 V6 and replacing 1 master cylinder the master has gone out 3 more times once every year after. Last year when it went out it backed up and leaked into the booster and I had to replace the brake power booster as well. It just baffles me why they are only lasting 1 year I've always bought new and not used or rebuilt OEM Motorcraft ones just like the stock one, but I even tried new aftermarket and the same crap keeps happening. Had to pay a lot of money each and every time because it would just be out of that 1 year parts and labor warranty except for this most recent time thankfully (it is in the shop now and should be ready on Tues) I'm about ready to sell it since it has had a ton of issues since the very beginning. Its ate a few sets of tires with barely any mileage or hard driving yet alignment/bushings/bearings/struts all check out ok, an alternator, plenty of batteries, the shaker system, electrical problems, engine and tranny problems, had to replace all 4 actuators because the ac/heat stopped working a couple of times and the blend doors would go out along with the electrical. Door leather came apart and everything looks bleached from the sun. As much as I like the car I don't think I'll ever buy Ford again ever in my life as avid as I used to be about buying 'em the imports look more appealing every day that goes by. Course nothing went wrong under warranty just immediately the month after it ended. Also took it to several dealerships and mechanics just to make sure. Only has 40k miles on it.