i have a 04 Sienna. The van was running fine until the starter went bad. But before that in the winter it wasn't heating very well. So while I was putting in a new starter I thought I would change the thermostat. i removed everything including the starter which made it easy to remove thermostat. Replaced and put it all back together. Car started fine but after driving about 5 miles i noticed the car overheating. I took everything back apart to the thermostat back to advanced auto parts and exchanged it for another. Put in the new part with gasket and started it back up. The hoses were soft both top and bottom. I filled everything back up with fluids and left the cap off for a while. I noticed the coolant started to overflow out radiator housing at cap. I replaced the cap and noticed it got even hotter gauge rising and both hoses top and bottom rock hard. The thermostat was installed with cone facing outward toward driver side fender. What could be the problem. It didnt overheat until I installed new thermostat. It is like thermostat is not opening. help please....I'm getting good at taking the thermostat in and out.