My original issue is an over heat. When investigating, I found the coolant hose flange on the driver side of the motor was cracked, an spraying fluid when the car warmed up. I replaced that, and the ECT sensor while I had those things apart. However, still getting the overheat. I found that hen the engine warms up, no coolant is coming back through the return to the overflow bubble, which points me to the water pump needing to be replaced. I'm going to replace it, and the timing belt since it is time for that anyway. But, before I get into that I'm wondering if the circulation problem could be the thermostat. If that is stuck closed, would it prevent the coolant from going into the radiator and then back to the overflow bubble, or is there another path that would get the coolant back to the overflow bubble? I will replace the thermostat when doing the water pump/TB service, since the coolant will be drained. I'm just wondering if a stuck thermostat would prevent coolant from returning to the overflow bubble. I;m not sure if it matters in this case, but it's a 2000 2.0 Automatic. When testing, I have been careful to turn of the motor when it starts to go above normal operating temp to prevent any damage. Thanks in advance for your insight!