Originally Posted by Huck
I agree that the cardboard only masks the problem, I've replaced my temp sensor and thermostat also, and still have the same condition as everybody else.
I have good flow at the radiator cap, so how can the water pump affect heat?
? If the pump is weakening, wouldn't it be heating up quicker?
That is the logical assumption. And in the big picture, yes. A symptom
of a failing water pump is the gauge sometimes reading wierd and a lack of heat. This happens because the waterpump can not adequately circulate water everywhere it needs to go. As a result, you get HOT spots and you get COLD spots. The heater is usually one of the first to be effected since it is the highest furthest away point. You won't see this failure by leaking coolant out the pump's weep hole. This failure is the pump's impeller vanes being rusted out to nothing.
So if your engine can't reach operating temperature or you don't have hot heat, chances are something is wrong. It could be -20 outside and the engine will still reach operating temperature just fine. And with a properly working pump and t-stat, it will maintain that temperature.