My 1995 Lexus ls400 heats up at idle, I have replaced fan clutch, thermostat, water pump, flushed radiator (and washed fins,condensor) , AC fan is working, gets air above thermostat at filler port, replaced overfill tank.....what the heck? This only occurs at low engine rpm's, typically when idling with ac on. In slow traffic (35) putting the stick in 2nd will raise rpms to 2k and temp will go down. I am not losing any antifreeze anywhere, but after about a week, the filler port above the thermostat will have air and will take about a cup of liquid....What the?