cooling system

The heat doesn't work properly (and it overheats which is another issue.) in the truck so we figured that there's air in the cooling system. But we had trouble finding where they are. Can anyone show a diagram or description of where it is located?

Hi there , I recently did a rad and heater core flush due to my heat not blowing as hot as it used to. After completing the job , I drive to work no problems , on the way home though the temp gauge drops to zero and it stops blowing heat. ( It is extremely cold here now -25 C). I have changed...