Whoops, I forgot to check my antifreeze and now It's freezing today, 8 degrees in KC.

First, my heater didn't work when I drove home from work. Then, my Civic overheated. It seemed to not overheat when I slowed down to get off the interstate.

I checked the coolant/antifreeze and it showed that it would not freeze down to 10 degrees, which I'm at, or a few below.

So I'm guessing that my water/coolant is starting to freeze. I had assumed that if it was marginal, that the heat of the engine would heat up the water, while driving, but maybe not?

So I need to warm it up, drain the radiator and put in more antifreeze

I have a theory that the water in the heater core has frozen, so it's not circulating. I have an idea that if I put a room heater from my house, in my car, that it might heat up the water in the heater core enough to get it circulating. What do you think?

My heater was working fine 2 days ago, when it was 20 degrees and my car didn't overheat.

2012 Civic Hybrid

Do you have any thoughts on my heater not working and overheating?

 

The ideal situation is to put the car in a garage, roll down the windows and use a room heater in the garage to get the temperature up. Be sure to remove any flammables lying around......

 

That worked, an electric room heater in the car, but it took about 6 hours to heat it up enough, at 5 degrees outside. The heater in my car works now, think I have the radiator filled with coolant, and it's not frozen. Hope it didn't freeze or break anything in the heater core.