I've had to top up my car's radiator fluid twice in the last month after discovering that the expansion tank (plastic container where one usually tops up) had completely drained out (roughly a gallon). The first time, I noticed a puddle of coolant under my car in the morning. I live in a hot climate and make heavy use of the A/C.
What possible reasons could cause radiator fluid to overflow? It looks like there is too much pressure inside the cooling system. Is this symptomatic of a clogged line or something else? If so, what action could be taken to minimize/eliminate loss of coolant?
My car has an LS1 engine, in case that matters.