west coasts come with a cast grille i don't think i have ever seen window screen
in a grille opening. not saying it hasn't been done, just seems a little weird.
the trapped air is legit in most cases, but the strange hose setup these cars have purges trapped air quite efficiently. the lower hose is normally only
a couple inches long in two places its mostly a metal pipe.
now that i am recalling my heating problems, the factory water valve for the heater was leaking (its a plastic piece of sh

bypass the heater hoses
for the heat temporarily and see if the temp goes down if so you have a leak
of pressure,in the valve or heater core. this sounds dumb but have you checked
the rad cap for deterioration?