2000 Plymouth neon overheating

i have a question as well....i have 2000 plymouth
neon.....i have replaced the radiator, thermostat,
hoses, and fan....it always runs cool. about last
week it started overheating..when i turn the car off
it fills up the reservoir boiling over....when i take
the radiator cap off it is bone dry i keep adding
fluid but noticed today that when i take the cap off
it starts to leak fluid from the bottom near the
belts...it also leaks when i squeeze the radiator
hose to check pressure...also while driving it will
start to overheat and then it starts to go back down
like all of the sudden