The thermostat housing on this car seems to have a bypass port that bypasses the thermostat. When I shake the housing, I can hear stuff rattling around in there, but I have no idea how it works or what it is supposed to do.
What does this "bypass" valve do? How does it work, how can I test it?
You can see it right here... his left hand is pinching the valve part on the housing:
https://www.youtube.com/watch?v=8sK1GMKPpD4#t=256