94 F350CCLB 7.3 T i.d.I.. Bought truck a year ago had brakes but did not feel 100% previous owner had replaced drums and rotors with new pads and shoes recently, he had also replaced a wheel cylinder which had been leaking, but he did not clean mess on shoes and drums. Thus the less than 100% feeling. So I replaced shoes and checked master cylinder - appeared low so I opened to put in some new fluid and heard a very loud sucking sound in master cylinder, after that pedal went to floor and no brakes. Took truck to Car X and had them power bleed brakes , still no brakes . Was told to replace master cylinder, did that and bench bled cylinder took back to car x and they power bled again - very little brakes, they said front hoses and vac booster replaced those took back for power bleed. Still no brakes. WTF Any help appreciated.