Brakes problem
2000 Ford Explorer V8 All Wheel Drive Automatic

my master cylinder is full of fluid. yet my brakes go all the way down and won't stop vehicle. i've looked at all four wheels and i see no leaks. i tried to bleed from master and fluid releases but not every time i release vaulve and brake preasure isn't building up. the automatic door locking system also stop working when the issue ocured.

please help ! mike