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?

[lagos]

keep the heater on full blast when you see it over heat. it will definetly help.
but try not to drive the car. you could really damage something.

thermostat is an easy thing to try, just to rule it out. but when was the last time you had your water pump changed? how many miles are on the car?

you should also check your coolant and your oil. check to see if there is anything in there that looks like coffee with milk.

[6strngs]

keep the heater on full blast when you see it over heat. it will definetly help.
but try not to drive the car. you could really damage something.

thermostat is an easy thing to try, just to rule it out. but when was the last time you had your water pump changed? how many miles are on the car?

you should also check your coolant and your oil. check to see if there is anything in there that looks like coffee with milk.

car has 154K miles. and I really have no idea when/if the water pump was changed. I bought the car at 144K and have done a ton of maintenance work to it since then, but no water pump. according to carfax, it had a major service done by a mechanic every 30K. so, if a waterpump was due at 120K, then I would guess it was done... but I can't be sure. I really hope it's not the water pump, I really can't afford to fix that. anyway, I'm off to change the thermostat right now, so I'll give an update after that's changed and a test drive.