Okay yous guys, now it's my turn to weight in. Unplugging the pressure differential valve switch made the light go out so we know it had a loss of pressure in one half of the system at one time. A leaking wheel cylinder general will leak too slowly for that to trip the switch unless it gets bad enough and the pedal is held down for a while. Ford was never smart enough to make that switch spring-loaded, but GM and Chrysler switches are. Very often it will stick after it turns on. A couple of quick, hard jabs on the brake pedal will get it to turn off. If that doesn't work, you have to pick one of the hydraulic systems and open a line or bleeder screw, then slowly apply the brake pedal until the light snaps off. If that doesn't work, then you have to open the other circuit and do that again. Do that with a helper running the brake pedal so you can tighten whatever you opened before the pedal is released, otherwise air will get sucked in.
If the light turns on again and the brake fluid level is not going down in the reservoir, suspect an internal leak in the master cylinder. If the fluid level is going down but no leaks can be found, check between the master cylinder and the booster. It it's wet there, the fluid is leaking from the rear of the master cylinder.
Sunday, March 18th, 2012 AT 10:26 PM