07 dodge charger overheating

I have a 2007 dodge charger that has about 240k
miles on it. After replacing the radiator, thermostat,
coolant tank, and ect. It still overheats. I have to
put coolant in almost every other day. The
temperature gauge goes to the mid point but
doesn't go past the mark. The a/c comes on and
blows cold air and both fans are turning. But for
some reason, when it's idling and the air is off, the
coolant fan would kick on (sounds like on high)
then coolant would stop boiling out of the
reservoir. The temperature gauge does not go pass
the mid point at all though. Any idea on what this
could be?