2001 dodge caravan 3.3l v6

losing antifreeze always same amount every time you drive the van and shut it off after shutting it off the antifreeze goes into the reserve tank it is filled to the top and comes out the overflow so i have to put more in instead of the radiator sucking it back in the radiator replaced thermostat,water pump fixed a hose checked for heater core its appears to be good accordingly to my mechanic heat doesn’t always put out heat plz help