WHILE DRIVING ANOTHER MOTORIST SAW SMOKE COMING FROM REAR OF VEHICLE AND GOT VEHICLE STOPPED ON SIDE OF ROAD AT WHICH TIME THE ENGINE COMPARTMENT WAS ENGULFED IN FLAMES. CALLED FIRE DEPT AND POLICE. FIRE SPREAD THROUGH THE HEARER BOX INTO THE VEHICLE AND ACROSS DASH UNTIL IT BEGAN BURNING THE HEADLINER. FIRE DEPT PUT OUT FIRE BUT WAS A TOTAL LOSS. THERE WAS NO INDICATION ON INSTRUMENT PANEL OF ANY PROBLEMS (ALL GAUGES SHOWING NORMAL READINGS). *TR