You cannot check it, it needs to be bled.
Remove the radiator cap and run the engine at 1200 rpm's, have someone watching the coolant level while you are keeping the engine running. Top off as needed. If it is air you should get heat after around five to eight minutes. Then top off coolant and install the cap.
Did you check the blend door?
Sunday, January 21st, 2018 AT 5:10 AM