Hello bitogers! I have a 2004 Toyota Sienna with 192k miles that is overheating. It started about a week and a half ago. As soon as it overheated I was lucky enough for it to be right next to the shop so I took it straight there (heater on high the whole way and all that jazz) Kept a close eye on it and just made it to the shop. Needless to say I had fingers crossed it was just the thermostat since that's a cheap fix. Lo and behold the thermostat was replaced and problem solved for a week (and 200 miles). Go to crank up the van this morning all was well so I thought. It was overheating again in the driveway here so I let it cool off and took it straight back to the shop (around a mile away if that). Now when it overheated both times there was steam coming out of the puke tank. I checked the antifreeze levels the first overheat and they were just fine. Even pulled the coolant cap off. It's a radiator cap but its not directly on the radiator. It's on a metal pipe at the top of the engine. Anywho my question is why the heck would the car drive perfectly for a week or so and then konk out with the same issue? Is it possible the new thermostat could be bad?