I need help troubleshooting a brake problem. The brake pedal goes right to the floor with no resistance. Checked the brake fluid and it was good. Got the idea that the mastercylinder was bad. Come to find it is an ABS hydraulic unit and Chrysler no longer makes it. Got one from a junk yard and for a moment it seemed like it would work. Same thing-brake pedal to the floor. So now the brakes were bled and still the same problem-the brake pedal goes right to the floor. Weeks later. The pump motor relay is bad. Replaced it with one from the junk yard and then it went out too. What would cause this to go bad?I don't want to get a NEW one untill I get this figured out. Or is that the problem, that I should put a NEW one in?