Mystery plastic piece found in thermostat

I'm curious about this too as I have the same car. The water pump impeller is metal. Check out pictures of it on Rockauto.com and you can see that everything they offer has a metal impeller. Even the cheapo beeps one. I would say it's part of the intake manifold or the radiator. Both have plastic components. I'd suspect the intake manifold first because coolant exits the engine there. A piece from the radiator would have to go through the water pump and possibly jam it. You'd definitely know if that happened! In other news, refilling the cooling system on this car is a special procedure. You must remove the cap from the plastic coolant recovery tank and fill the system through the thermostat housing. Once you do that, put the thermostat housing back together and top off the plastic recovery tank and start the engine, with the cap still off. As the engine warms up top off the recovery tank as needed until the engine is fully warmed up and the level in the tank stops going down. Hope that helps! Jim

Thank you Jim! I don't know a lot about cars but I'm cheap and have the time to learn. I didn't know that about refilling the system so very helpful! I'll check the intake manifold next and update when I find the cause. Thank you.

You're welcome. Glad to help! Most people don't know about the refill procedure, so that's why I mentioned it. Yes, please keep us posted! I'll be curious as to what you find out! Jim