[gr8shot]

Ok, have you tried the basics, like flushing the system, washing out the radiator stack, replacing the thermostats, things like that?

Does the fan ever come on when it starts to get hot? usually the fan will come on and cool it right back down. You'll KNOW when the fan comes on, it's unmistakable. I'm betting your fan clutch is probably bad.

 

[gr8shot]

You will KNOW when the fan comes on. It's unmistakable. You literally can NOT miss it, it's like a freakin jet engine lol. So I'm sure for some reason your fan clutch isn't engaging. My best guess would be to get a new fan clutch. It should come on way way before you ever get hot enough to set a light or anything. I guess I don't know if it defaults to locked or not when it fails, but in this case it's obviously not coming on when it's supposed to, so I'd replace it, and it sounds like that should fix the problem.