WE WERE DRIVING DOWN THE HIGHWAY AT 75 MPH I SMELLED SMOKE COMING FROM THE ENGINE COMPARTMENT. TOLD THE WIFE AND KIDS I WAS PULLING OVER AND TO GET READY TO BAIL OUT OF VAN AS SOON AS I STOPPED AND TO STAY CLEAR OF IT. WHEN EVERYONE WAS OUT AND SAFE I OPENED THE HOOD AND SAW A FIRE UNDER THE MASTER BRAKE CYLINDER. GOT WATER BOTTLES FROM INSIDE VAN AND A RAG AND PUT THE FIRE OUT. THERE WAS BRAKE FLUID ON THE SWITCH BELOW THE BRAKE MASTER CYLINDER ON THE WIRES TO A SWITCH UNDERNEATH. LATER I CLEANED THE MESS CUT THE WIRES THAT HAD CAUGHT FIRE THE ONES THAT WENT TO THE SWITCH UNDER THE MASTER BRAKE CYLINDER AND WRAPPED THEM SO THEY WOULDN'T GROUND OUT.CONTINUED ON HOME FOR ANOTHER 1 1/2 HRS. WHEN I GOT HOME I TOOK THE SWITCH THAT HAD BURNED UNDER THE MASTER BRAKE CYLINDER OFF AND PUT A BOLT IN IT'S PLACE.I THRU OUT THE SWITCH. I HAVEN'T REPLACED THE SWITCH I ALSO LOST MY CRUISE CONTROL SINCE THE FIRE. I DIDN'T THINK ANYTHING ABOUT IT UNTIL TODAY WHEN I WAS LOOKING UP SOME INFO FOR MY VAN AND READ THAT THIS IS A PROBLEM .