Thermostat
So, turns out my car's problem was a (fucking) thermostat and thermostat gasket. $25 worth in parts, over $100 worth in labor, and $80 worth in car rental fees.
I could have fixed that on my own in twenty minutes. And I would have, if I had reason to suspect a bad thermostat. The only reason I didn't is because I put two in my car last year when it had heating problems. I'm more inclined to think that it may have been the gasket itself, as I have no idea how badly mauled it got when my car was being worked on last year, and it's a pretty massive gasket on that thing.
So, looks like I have to feed my car a thermostat every year.
I could have fixed that on my own in twenty minutes. And I would have, if I had reason to suspect a bad thermostat. The only reason I didn't is because I put two in my car last year when it had heating problems. I'm more inclined to think that it may have been the gasket itself, as I have no idea how badly mauled it got when my car was being worked on last year, and it's a pretty massive gasket on that thing.
So, looks like I have to feed my car a thermostat every year.