On a '91 Alfa, V6. The brakes are sticking, eventually locking. It started while driving but now does it just running but not driving (with no stepping on the pedal). I'm assuming it's the servo. The valve that equalizes pressure on both sides of the diaphragm is allowing engine vacuum into the constant pressure chamber only? But I was curious to hear if anyone has experienced this problem. I can't think on anything else it could be. Thanks for the help.