On the 4.7 liter you don't use the radiator cap to get all of the air out of the system. Where the upper radiator hose meets the engine there is a fill plug that looks just like the fill/drain plugs on the front differential. With the radiator cap on, take out that fill plug and add coolant through that fill plug. Then start the engine with the heat on with that plug still out until all the air bubbles come out that hole. Then reinstall fill plug!