low coolant light comes on at startup, but disappears once car is warmed up. but this morning and yestrday afternoon it didnt, the weather was warmer. is it telling me the amount of coolant itself is low compared to the water in the tank as well? there are no problems as far as operaing temps, stays right in the middle, so it is being cooled fine. is this a sign the water pump is about to go? or is it just a matter of flushing the rdiator and prepping for winter?