Having been on the road 2 days after going for a short test ride it looks/seems like it takes a good day or 2 to totally get all the
air out of the coolant passages.
I'm missing a few things here. Did you drain and refill the coolant? Usually, there is a high spot in the cooling system where you can bleed the air out. This may be in a crossover cooling tube with the small lines coming off to go to the fill tank. This way, you get all the air out and all the coolant in. Some vehicles will overheat as the air gets trapped and the water pump can't pump. Always good to watch temp after a coolant change to make sure it's stable at the normal temp.
Pierce
Indeed quite normal after draining cooling system. Takes awhile to get all the air out of engine, radiator and especially the heater core.
unless you vacuum fill the system, then almost no air.
Could somebody please explain how a paid for vacuum process can get trapped air out of high points that don't drain air. Makes the bubble bigger for sure so it may leak out past a casting obstruction. May wreck havoc on seals. Engine will pull a natural vacuum when it cools. Once pressurized Velocity/turbulence carries the microbubbles out of the head galleys. Crossover tubes rising out of the heads is a bonus. But it just takes time for air/steam to exit. Ultimate engine may well feed the cylinder heads first with coolant and then flow downward to the cylinder bores to maintain thermal Harmony.
When the system is put under vacuum the coolantis actually drawn to the very spots that typically trap air. The more prone a spot is to getting some air trapped the more it pulls the coolant into that void. You don't pull a lot of vacuum. It works fantastic no running and bleeding process. The only time I have seen it get blamed for starting a leak was on a very sketch and rusty looking metal reservoir tank.