Yes on a tractor, but the kind of engine fire I was referring to was an automotive vehicle fire.
Under the hood there are lots of plastic things that will burn when the temperature gets high enough, including the paint. You have an air box, heater box, fan(s), wiring, battery covers, engine covers, hoses, belts, etc.
I occasionally saw vehicles with these kinds of fires, or vehicles that nearly had these kind of events, working in the automotive repair business. These engine fires were usually the result of either the exhaust overheating due to the catalytic converter(s) being blocked, (I won't explain how that happens here, but it is easy for this to happen if you have a problem with your engine), or an electrical short. Yes, there can be other causes, but these are the most common. Both of these events can produce temperatures that result in red hot glowing metal. I personally have seen about a half a dozen glowing hot catalytic converters over the years. These vehicles were minutes away from going up in smoke.
Because of the extreme temperatures involved, you will find you probably cannot put one out with a fire extinguisher. The firemen who eventually put the out fire I attempted to extinguish, agreed. This is because you probably won't be able to get the hood open, and the extreme heat will keep reigniting it until you run out of extinguisher.