Here's a basic question:

Without a temp gauge, how do I know if my engine is getting close to 
overheating. I know the engine compartment seals should be in good shape, and 
not to overwork the engine, blah blah blah. I know the preventative measures, 
but if I'm driving mountain passes on a hot summer day how do I 
know if I should pull over and let it cool?

Thanks,

--Jonny