Engine Overheating

I am at loss as to what is wrong, I have checked everything I know of. Here is what I do know. Engine is overheating. The coolant is not leaking. Radiator when cold, has plenty of coolant. When engine get hot all the coolant seems to be draining into the coolant reservoir. Top Radiator hose is getting warm. Lower Radiator hose is staying cool. Heater is intermittent, doesn't always blow hot. When is blows hot air the engine doesn't overheat. When it doesn't blow hot the engine gets hot. Sometimes there is an awful screeching noise when I start the car. I just replaced the Blower Motor. GM shop said it was going bad. They said since it was going bad this could cause the heater to not work properly and could cause the engine to overheat since the blower motor was not properly pulling the heat out of the engine compartment properly. Still no heat, but the AC blows really well now. Lol. And the engine is still overheating.

I can only think of 1 or 2 problems.
1. Water Pump is going out. Screeching noise.
2. Thermostat is stuck closed.

What do you guys think? Thanks