Any Toyota Techs on here?
I have tried burping it. My driveway is a hill. Parked in the middle, took the cap off the radiator. Let it run for like 20 25 minutes.
You definitely cannot count on that to purge all of the air trapped in some systems. Take the
highest coolant hose in the system off and see what comes out, and with the cap off if the
level in the rad starts dropping when You do.
As far as the heater control valve, can't remember on that year, but most are vacuum control.
And most are designed to default to open so that You have heat to safely defrost the windshield in the winter, so unless the controls are holding it closed by some malfunction, it
should be wide open. How do the hoses feel temp-wise in vs out?
As TJ said, even at an idle, there should be a reasonably brisk flow of coolant visible in the
rad w/the thermostat open.