GOING OUT OF DRIVE BRAKE PEDAL WENT TO FLOOR. LATER TURNED OUT TO BE A BRAKE LINE RUPTURED FROM BEING CORRODED. TRUCK ROLLED BACKWARDS AND STRUCK A TREE CAUSING MINOR DAMAGE TO THE BUMPER. NOT REPORTED TO INSURANCE BECAUSE DEDUCTIBLE HIGHER THAN DAMAGE. THIS FAILURE OF THE BREAK LINE HAPPENED ONCE BEFORE IN 10/2009. LUCKILY NO INJURIES BUT THE NUMBER OF THESE INCIDENTS POINT TO A HAZARDOUS FLAW THAT GM SHOULD ADDRESS. *TR