Ok so I have a 2004 Honda Civic coup and its been overheating recently. It started about a month ago and its stumped my mechanic and me. There are no leaks, from the water pump or the radiator and each thing we do to the coolant system seems to fix it for a couple of days then all of a sudden its starts over heating again. The weird thing is that the coolant/antifreeze mix that we put in is just backing back up in to the overflow tank and we have no idea why. We've changed the thermostat twice because the first one was bad right out of the box supposedly and the radiator cap but nothing is working it all seems to mask the problem for a couple of days to a week then the problem rears its ugly head. Now everything i have read about water pumps going bad is that you'd be able to hear it, see it leaking, and certain things in your car such as the AC would stop working as well as it had been but everything is working just fine, the AC is literally so cold that it freezes me out in the hottest of days and there is no clicking or leaking coming from the water pump. I'm pretty stumped and have almost decided to take my car in to the woods and shoot it, Can anyone maybe give me a hint to what might be the cause of the overheating, or some other suggestions to what it might be. Much appreciated.