overheating, I'm stumped. Options

[6strngs]

so today, I drive my car home from work. get out of the car and notice a strong coolant smell. I let it cool down for a while, then went out to check it. The radiator was still full with coolant, but the overflow tank was kinda low. so I poured some coolant in (pre-mixed 50/50). anyway, so I go to drive the car again and after a short trip, only a couple miles, I'm hearing this weird whining sound. I glance down and see that the water temp gauge is reading HOT! like, it was all the way into the red! I pull into the closest parking spot and shut off the car. I let it sit for about half an hour and decide to drive it back home. I start the car up, and the temp gauge jumps to 1/2 way. normal. and as I start driving, it starts climbing. it gets to about 3/4 of the way to hot and then very suddenly just drops back down to half. then it stays there the rest of the way home. I pull into my garage, and get to work. I tried my best to track down a leak and decided it appeared to be that the hose that feeds coolant to the throttle body was leaking. so I replaced it. so after a couple hours of work (decided to do some other stuff too since I had everything taken off anyway) I go to drive it again and same thing. the temp gauge reads normal, then it will climb in temperature, then drop back down to normal, then climb again, then normal. anybody have any ideas? thermostat? water pump? malfunctioning sensor and/or gauge?

[Batman722]

definatly change the thermostat, it's bad at this point. Be careful how much you drive with it overheating like that, you could kill your headgasket.

also, before it overheats, do you drive it hard or just normal (lower RPMs) driving ?

[6strngs]

definatly change the thermostat, it's bad at this point. Be careful how much you drive with it overheating like that, you could kill your headgasket.

also, before it overheats, do you drive it hard or just normal (lower RPMs) driving ?

ok, will change the thermostat asap.

and, the first time, when I drove it home from work I probably drove it a little hard, like revving to 4500 a couple times maybe. after I smelt the coolant I took it easy and shifted at 3000-3300. and after it overheated I took it as easy as I could on it and shifted it at 2700-3000. also, I was told turning on the heater was good for cooling down the engine because you use the heat from the engine to heat the air coming in. I don't know if that's true or not, but after it overheated I turned the heater on full blast. I don't know why, but it would only blow lukewarm air in when the temp climbed above normal, then after it dropped back down to a normal temperature the air coming in would be hot.