2010 Sienna overheating

Have a 2010 Sienna CE with 196000 miles. It developed a
slow coolant leak about 3 weeks ago. Overheated on the
highway one time, and then saw coolant smoke from under
the hood.  Couldn't identify where the leak was. I replaced
the thermostat, and water pump. Tested the radiator for
exhaust gasses which was negative.  Now when I drive it
will start to run just a little hot especially at idle, but can
under way also.  Coolant seems to be still leaking slightly.
Both cooling fans are operating although as it gets hot they
get very loud, I assume to pull in extra air.  Not sure where
to look next. No smoke out of the tailpipe either.