I suspect this is a blend door actuator issue and not necessarily a coolant issue. It could be a heater core but I would start with the actuator and make sure that is functioning properly first.
Here are guides that will help with this:
https://www.2carpros.com/articles/car-heater-not-working
https://www.2carpros.com/articles/replace-blend-door-motor
Then if the heater core is still an issue, you will not be able to flush it. These are called multipassage units which means if there is a restriction or a blockage it will just find another path and not remove the blockage. If that is the issue then you will have to replace it. However, I doubt that is the cause so let's check this first.
Let me know what questions you have. Thanks
SPONSORED LINKS
Monday, December 7th, 2020 AT 8:31 AM