1993 6 cyl Corsica Over heating

My corsica seems to be wanting to over heat on me, but when i cut the heat on it keeps it cool enough (well at least thats what the gauge says). I recently discovered the fan wasnt working but got it re wired so now it works and actually stays on constantly while the car is on. Last year the thermostat went bad and we changed that. It doesnt seem to be leaking coolant any where. Does anyone have any ideas, i dont really have the 24 dollars to fork over for another repair manual. My friend seems to think its a small part within the water pump but doesnt know the name of it.