I had a similar issue when I replaced my rear calipers. I would get fluid through but in my case my e-bake wouldn't even hold very well. My buddy who is a mechanic said to hit the pedal with a mallet. I did and it worked. Just a thought. Good luck
02 Mustang GT Hard Top. 3.73 rear, CAI, No A/C,Performance suspension, Straight pipes from the cat. Bama Tuned. Rear upper and lower control arms with poly bushings.
Future mods: Cam, 3.9 rear, better suspension, Lightweight drive shaft, subframe connectors, larger tb, Long tube headers with electronic cutouts and SLP LMII's, SCT tuner, better wheels and tires, possibly a 2500 torque converter.