Bleed. I think it was impee that has a pretty good bleed method. Fill up with water till it comes out bleed screw with heat on. Put cap on and screw on bleeder screw but don't tighten all the way. Then start the car and Rev it a few times, not too hard though. Turn off and rebleed. After You bleed several times turn on the car with heat on full blast and wait till it gets to operating temp, if heat blows hot your good...if it doesn't rebleed...