WAS DRIVING ABOUT 20 MPH ON A 2 LANE SECONDARY ROAD WHEN AN APPROACHING VEHICLE'S DRIVER GOT MY ATTENTION AND SAID MY CAR WAS ON FIRE. I FOUND A PLACE TO SAFELY PULL OFF THE ROAD AND DIRECTED MY SPOUSE TO QUICKLY GET OUT, MOVE AWAY FROM OUR CAR AND CALL 911. THERE WAS SMOKE COMING FROM UNDER THE HOOD SO I OPENED IT CAREFULLY AND SAW A WALL OF FLAME, JUST ABOVE THE CATALYTIC CONVERTER, AND APPROXIMATELY THE WIDTH OF THE RADIATOR AND ABOUT 6 INCHES IN HEIGHT. I HAD A BOTTLE OF WATER WITH ME WHICH I USED TO DOUSE THE FLAMES BEFORE THE FIRE DEPARTMENT ARRIVED. I HAD THE CAR TOWED TO MY LOCAL REPAIR SHOP WHERE OUR MECHANIC FOUND A BURST TRANSMISSION FLUID COOLING LINE WHICH HAD SPRAYED FLUID INTO THE LOWER ENGINE COMPARTMENT AND ONTO THE HOT CATALYTIC CONVERTER WHICH IGNITED THE FLUID. JUST BEFORE I PULLED OFF THE ROAD THE TRANSMISSION STOPPED OPERATING EFFECTIVELY AS I NOW KNOW THE FLUID WOULD HAVE BEEN LOW. AT A HIGHER SPEED THE VEHICLE OPERATION WOULD HAVE BEEN DRAMATICALLY HAMPERED AND THE POTENTIAL FOR A MORE EXPLOSIVE SITUATION WOULD HAVE OCCURRED IF THE FLAMES HAD BEEN FORCED FURTHER UNDER THE VEHICLE.