Just changed my rotors and pads, but now my brake pedal goes slowly to the floor before my brakes engage. when stopping from high speeds my brakes will even lock up and cause the car to skid/hop. i bled the lines three times but it doesn't help. could it be the master cylinder??

 

Yes, the master cylinder could be bad. Problems can occur when manually bleeding brakes: in normal braking, the piston in the master cylinder normally moves a small amount, when you manually bleed it, the piston travels the full bore of the cylinder for the first time in years and the rubber seal passes over corrosion that has had time to build, destroying the seal.

Bleeding would be the first thing to check, so you've been taking the right steps. Air in the system would not cause locking up, however. Good luck with the repair.

MechanicSpeak
www.mechanicspeak.com

 

bleed the master cyl

 

It would help us help you if you told us EXACTLY what you bled and in what order. And pls explain why you bled the system 3 times if you did it correctly the 1st time and it didn't work. Doesn't make sense.