Abs, Prop Valve? - Soft brakes after swap

Hey Guys,

I recently swapped in a c8.25 with discs in leau of my old d35. The swap went fine, but now my brakes are very spongy. I have bled my brakes 4 times, then took the jeep to my mechanic to use his bleeder machine, and still very soft brakes.

Any Ideas? I push the brake pedal and it stops for a moment, then goes straight to the floor, then i have real pressure and can stop the jeep. The brake light comes on when it goes soft.

I have the xj prop valve and have not removed any ABS.

Thanks!