BRAKE LINE RUPTURE AND RESULTING BRAKE FAILURE CAUSED MINOR REAR END COLLISION WITH VEHICLE IN FRONT. AIR BAG ACTIVATED BUT STRUCTURAL DAMAGE MINOR UNTIL THE FIRE. FIRE ORIGINATED IN FRONT LEFT (IMPACTED) CORNER AND CONSUMED ENTIRE ENGINE COMPARTMENT TO THE FIRE WALL. WEATHER PERFECT, DRY ROADS, NO OBVIOUS CAUSE OF FIRE. EXCEPT FOR BRAKES VEHICLE WAS DRIVABLE UNTIL FIRE. *TR