I love your show and try to listen every week. On show # 1147, Lana has a car (Mercedes?) where her heater does not work at idle, yet it works when she is driving. You overlooked one simple feature of a cooling system--the thermostat. Since thermostats are designed to open at a particular temperature, it is possible that someone installed a thermostat with a much higher temperature rating than is designed for the car, which would prevent the coolant from flowing until the engine heated up. Since it is typically two screws and a gasket and generally easily accessible, checking the thermostat should always be done before considering the replacement of the water pump (expensive). Is there a way for people to instant message or email you during the show so you could receive suggestions from the audience? You could give a simple prize (or just free recognition) to the viewer that came up with the correct answer.