I have a jeep liberty 2010, 3.7. I changed thermostat, flushed radiator and heater core. Put in coolant. I get heat as It wasn't putting out heat before. But now it only heats while driving on the road. It doesn't throw out heat while idling. What do you think is the problem? I read here it could be water pump. But wasn't sure about that. Has has anyone else experienced something similiar and what was the fix?