I have a 2000 Mercury cougar v6........It keeps over heating...I would like to know is this expensive cost to fix....?

without actually being there to check it out all i can do is give you a couple ideas on things to check, if you havnt got it fixed yet does the radiator have fluid? is it low? if its full of fluid, you might want to drain it and start with new stuff, not sure where you live, but here where i am, in n.w. colorado, during the summer depending on the vehicle its best to use a 60:40 ratio of water to antifreeze, the water disipates the heat a little better, but in the winter we run the exact opposite most of the time if thats not the problem you could very well need a new water pump or you mite to clean your cooling and heating system, sometimes minerals from the water start to build up and plug the the system, much like a blood clot on a human if none of these help or are even the problem you mite to change your oil, or add it, not knowing how much your engine goes through if it burns it or not, but check the radiator, and the oil levels first, usually those are the most common issues

could be thermastat or there r 2 belts on motor one on each side the one on driver side is small goes around 3 pullies one of them is the water pump it is under plastic gaurd hard to c but 2 or 3 screws and your there