2000 GMC K3500 REG. CAB PICKUP 4X4 -- BRAKE PEDAL GOES TO FLOOR AND ABS SYSTEM ENGAGES. VEHICLE HAS EXTENDED BRAKING DISTANCES ON DRY PAVEMENT. BRAKE LIGHT COMES ON AND GOES OFF AFTER RE-APPLICATION OF BRAKES BY "PUMPING" THEM. PEDAL ALSO GOES TO FLOOR WITHOUT ENGAGEMENT OF ABS SYSTEM AND VEHICLE WILL NOT STOP. PROBLEM HAS BEEN RECURRING FOR THREE (3) YEARS BUT THIS TIME VEHICLE WAS INTENTIONALLY DRIVEN INTO A SNOWBANK TO PREVENT A COLLISION WITH ANOTHER VEHICLE. ON 06/24/2010 DRIVER REAR BRAKE LINE (STEEL) ROTTED THROUGH WHERE IT TOUCHED FRAME AND EXPELLED ALL BRAKE FLUID FROM MASTER CYLINDER ALSO CAUSING BRAKE FAILURE.OTHER LINES ALSO SHOWING PREMATURE CORROSION. BRAKES ALWAYS HAVE A SOFT AND SPONGY FEEL EVEN AFTER REPLACEMENT OF FLUID AND BLEEDING OF ENTIRE SYSTEM. PARKING BRAKE CABLE (FRONT) ALSO SNAPPED DUE TO CORROSION AT UNDERSIDE OF CAB. *TR