2011 Impala bleed coolant

Just changed the radiator on my 2011 Impala. It is an LT model that has the 3.5 engine with 81K. Noticed there are no bleeder screws for the coolant. I'm getting a noise thru the heater core like coolant is trying to bleed off, but it never goes away. I've tried running with the radiator cap off, and tried running the car for 45 minutes with the car jacked up on the passenger side.

Any ideas would be greatly appreciated!