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]

lighten up guy and do some research, do you work for toyota ?

you should know that air and air bubbles could be found in the liquid that cools your engine. This may not be a big deal to you but remember that if this is the case, your engine could actually overheat. That is why it is important to remove any air in your coolant reservoir.

You just add to the radiator a mixture composed of half water and half antifreeze. Make sure you fill it right up until the top portion. Then, do the same to the overflow or coolant reservoir.

After doing such, just leave the cap of your radiator off and let the engine run. You would know that the radiator has already removed the bubbles because there would be a large air bubble come to the top or you would see the coolant go down. When this has been successful, refill the radiator with the right amount of coolant. And you can turn the cap of the radiator back on.

"Burping" the cooling system allows trapped pockets of air to escape: Air pockets can cause overheating because there will not be enough coolant in the cooling system, even if the radiator and coolant reservoir look full.
Instructions
STEP 1: Add a mixture of one-half water and one-half antifreeze to the radiator. Fill it right up to the top. STEP 2: Fill the overflow/coolant reservoir with the same 50/50 mixture. STEP 3: Leave the radiator cap off, turn the engine on and let it run until the radiator "burps": You will see the coolant level drop and may see or hear a large air bubble come to the top as the system burps. STEP 4: Keep an eye on the temperature gauge throughout this process. STEP 5: Refill the radiator to the top and coolant reservoir as needed. STEP 6: Put the radiator cap back on. STEP 7: Note that if the engine runs hot after this procedure there may have been another pocket of air that "burped." Let the engine cool down and then add more coolant to both the radiator and the coolant reservoir.

just 2 quick articles I found when I googled "air bubbles in coolant".