I recently drained quite a bit out of the cooling system from my '98 2.5L when I disconnected the coolant bypass hose at the engine block which runs up to into intake manifold so I could remove the intake manifold. I captured all the coolant that drained out, maybe a good gallon and a half I'd say.

Now after refilling the cooling system (after reinstalling the intake manifold), the coolant level is full in the radiator and in the overflow tank before I've replaced all of the coolant which originally came out. I'd say I've still got close to a third of a gallon remaining. When I refilled the coolant I made sure the heater valve was open, and I've run the engine and driven the truck around a few days now, topping off the coolant as it would take more.

But it seems to be remaining "full" now when I check the level, not going down anymore to accept the remaining amount of coolant which was in it previously. This leads me to believe there must be an air pocket within the coolant system that would need to be bled out. However, there seems to be no sign of abnormality otherwise; the heater is putting out good heat, the temperature gauge is acting normally, and the engine is running normally.

Is there some trick to making sure all the air gets bled out of the cooling system for this engine? Should I just wait it out with a few more days of driving around and figure the air will work itself out and top just top it off gradually off as it might finally accept the remaining coolant?