Weird cooling system behaviour

I would take the radiator hose loose on top of the thermostat housing on the motor, look down in the housing and see if there is a thermostat. If there is one shine a light down in there and see if it is stuck open. If isn't one a 180* or 195* would be good enough.

Drain the radiator first then take the hose loose. After you're done make sure you have a 50/50 mix of coolant and water. Fill the radiator until the you have covered the radiator core about a 1" or so. Crank the car and let run without the radiator cap on until the thermostat opens and you see the water/coolant go down. Add until it water/coolant is fairly close to the top of the radiator. Try to see that you have flow while you are doing this. This baiscally the way I feel my system. It does not check things such as the raidiator cap and so forth.

I always dill a 1/16" hole in the thermostat to allow air to escape.