Thermostat, expansion tank, and radiator hoses replaced. Donezo. Coolant bled and no more air bubbles. Fantastic. Still no mother fucking heat. The lines going in/out of the heater control valve don’t get hot at all, but it feels like the return line from the heater core to the expansion tank is heating up. Da fuq? At this point I’m thinking someone bypassed the heater control valve and is just running the coolant from the heater pipe off the engine and back into the expansion tank, but the dealership would have hopefully realized this when they inspected it. The HCV sounds like it’s working; I can hear/feel the valve operating when I connect/disconnect it while the ignition is on. I might try letting the car idle up to temperature and then disconnect the HCV wiring to force it open.
Looks like I’ll be dicking around with this all weekend.