Had my first one of the season with the usual not enough heat from the vents. While the heater core replacement is recommended too. Depending upon the severity, this coolant flush procedure may also do the trick. Either way it's the first step to replacing the heater core so might as well try it and see. I decided to make a video of the the procedure we use at my shop that is tried and true. Hope this helps!

 

Hope this has helped some!