Why does my car have no heat even though I flushed the heater core? This video shows you exactly why. A partially plugged core will cause you to have heat only on the part of the core that the hot water is freely flowing through. We took this heater core out of the vehicle, cut it in half into sections so that you can see where it’s clogged, and how water can flow right through from one into the other, and be perceived as, good coolant flow and a core that is not plugged when actually it is very plugged. It only takes a very small amount of the heater core to be open for water to flow freely through it so it can be very misleading. We hope this helps you. Take care of Buddy and will see you on the Under The Hood Radio Show.