Hello to everyone. I own a 2006 Buick Lucerne with the 4.6 Northstar. About 8 months ago she started overheating with the gauge jumping up to the top and the message near the odometer saying that it has shut down the a/c then said to shut the engine off. I did notice that the hose leading to the thermostat was rock hard, so I replaced the thermostat. I purchased one from the local autozone in town and noticed it did not have the hole in top of the thermostat, so I purchased one from the dealer which was exactly like the original. Everything was fine after changing the thermostat, so I took it to the dealer and had them flush it and put new coolant in. The car has just turned 50K and it is starting to overheat again. I am puzzled because the coolant level is fine. When the temp is close to overheating, I put it in neutral and rev the engine. The heat in the car gets nice and hot like it should and then the temp gauge goes down to normal. I have noticed that the heat in the car does not blow that warm when it is getting close to overheating until I rev the engine. I want to say that the waterpump is bad but don't want to just start changing parts because I am unemployed until I can find a new job. Many thanks in advance.