I had a similar thing on my 750 except mine didn't catch fire. The Water pump siezed and it started pouring out antifreez from the pump shaft. When I got the car towed home cause I was driving it when the pump went out and I couldn't shut the engine off right then cause the road had no shoulder I had to go to a side street. But when I looked at it at home I found that the pulley part that went into the engine block was bent and that was why the pump went out I still have no idea how it got bent inside the block but it did. Now I have a new water pump in and the car runs great.