When I first replaced my coolant on my NA car, 2008, I never got it to fully bleed, using the bleeder screw and having the rad cap open. I always heard air bubbles in the dash after shutting the car off from that day forward, until I did my hv3.
I didnt torque the plenum bolts down right so I ended up getting a massive coolant leak when I was trying to leave work one day. Bolted everything down tight, filled the coolant back up in the parking lot, started the car and I let it bleed for almost a half hour and I still heard gurgling when I got into the car.
In the stress of the moment, I actually forgot to close the bleeder screw before I left to drive home and about half way home I stopped hearing the gurgling. Opened the hood when I got home and discovered the bleeder was open, cranked it shut. Never heard the bubbles again.
My thought is that from going up and down hills, revving the motor and slowing, etc as part of normal driving, the motor was put through all kinds of up/down angles and engine speeds and that did a lot to work the air out of the system. From then on I've always suggested people let the car warm up and then take a short spin around the highway with the screw still cracked open.
