My 1982 240 wagon has a stubborn brake problem. It feels like I'm not getting complete braking. It takes an unusual amount of force on the pedal to get even mediocre braking. So far I've replaced all 4 calipers, all the pads (mintex) and the two rear rotors. Nothing has worked. The master cylinder was replaced a few years ago and does not leak. The pedal is hard and will not sink no matter how hard or how long I stomp on it. I tested the vacuum to the brake servo and it seems to be pulling a reasonable vacuum. The check valve appears to work properly. I'm going to park this car before I get into an accident on the highway unless somebody can give me a diagnosis.