Yes, never shut it down with the cap off.

Here is the usual way to bleed a 3800 engine- let it idle rad cap off till the fans turn on, (when the fans are on the temp is over 195 deg, the t stat is wide open) then open the bleeder screw on top the t stat housing a few turns till a steady stream of coolant comes out the hole, shut the screw, top off the rad. with coolant and cap it.