1973 Eldorado (acting weird)

i have 73 eldorado which sat all winter but i'd go and start it once a month or smth, and it would do just that without problem. As it warmed up and i began working on its body but it wouldnt start without a jump now, even with a jump it would just tick and I'd have to wait with my jump cables from my truck running for like 5 min then it would. Today i left it running for like 15 min to charge up the battery and it got really hot, the exhaust was red hot (im not even talking about the engine itself) so i drove it into garage and when I turned the engine off, something under the hood was still turning for like 15 sec, shaking the whole car, sounded like something got snapped and then this sound like as if it was an old steam train or smth, like lots of hot air escaping from somewhere. I've no idea what that was but, any ideas? Thanks

It sounds like it may have been severely overheated and got so hot it continued to diesel. I saw this years ago on a neighbor's Rambler. I finally got it to stop by pulling the air cleaner and holding a wadded up rag over the carb to suffocate it. How is the coolant level and the belt driving the water pump? It is possible the thermostat stuck closed.