Update - car's heat is still working today. After posting, I did a better job of searching this site and it sure seems like many people are getting air trapped in their system. The purge done properly is important.
Oil looks good so I don't think it's a headgasket. Which elbows? Could this cause the coolant to sometimes get to the heater core and sometimes not? Because after I purged the air, then the car heated awesome. I'll keep everyone updated.