Chrysler Repair: Chrysler LHS overheating, water pump impeller, radiator coolant

Question
Hi Roland, I realize you have had more than your fair share of overheating chrysler engines questions. I have a 99 Chrysler LHS 3.5 L. I understand, thanks to your previous answers, that the culprit, could be a thermostat, a radiator, coolant level, water pump, or a coolant leak. In my particular situation, I was driving last week and the engine heated up on me, I pulled over and stopped the car. A couple of seconds after, it started smoking. The car now is in my garage. I am trying to diagnose the issue. When the car is in idle, the gauge shows 3/4 within 20 mins of starting the car. The fans come on when the gauge is at 1/2. The upper hose is hot, but it's not hard. The radiator is cold all over. The lower hose is at room, non operating temperature If the upper hose is hot shouldn't that mean that the thermostat is open and flowing coolant from the engine ? Can you somewhat pinpoint where the problem is ?

Thank you in advance for your answer.

Answer
Hi Zied,
If the lower hose is cold, then that suggests that the flow of coolant across the radiator and to the exit at the lower hose is very restricted. Normally the tank on the right side is hot and the tank on the left is also hot (maybe a little less hot) but if it is cold then there is no flow getting across. So my thought is you need to get the radiator unplugged or replaced. The only other possibility is that the water pump impeller has come loose so you have no pumping of the coolant. The thermostat is open as evidenced by the hot top hose.
Roland