Odd recurring heat problem, 2007 Impala

We have a weird issue with our Impala currently. In the mornings, we start the car, and get no heat for 5-10 minutes, unless we rev the piss out of it while under load (driving very aggressively.) Even once the heat has started, if we don't maintain 1500+ rpm, we lose the heat, and it starts blowing cold. Below 2k rpm, it is only lukewarm. Also, as it heats initially, it goes from cold, to the middle, to almost in the red, then we get heat and it settles back down to the normal range. Last year we had a new water pump put in (due to the same issue) and the system flushed, although that only partly fixed it, and only for a couple months.

I am thinking maybe stuck thermostat and/or air in the system, but I wanted to get some opinions before hammering away at it. Thanks in advance!

Sounds likke air in the cooling system, needs to be bled, there a bleeder on the T'stat housing. warmed up, hold the engine at 1k open the bleeder, let it run oun out till no air bubbles, need lots of rags here.

I would recommend taking the vehicle into your local dealership to be diagnosed. They should be able to assist you further and have a plan for addressing the issue. If you have further questions, please feel free to contact me directly. Thank you.

Tricia, GM Customer Service.

We have a weird issue with our Impala currently. In the mornings, we start the car, and get no heat for 5-10 minutes, unless we rev the piss out of it while under load (driving very aggressively.) Even once the heat has started, if we don't maintain 1500+ rpm, we lose the heat, and it starts blowing cold. Below 2k rpm, it is only lukewarm. Also, as it heats initially, it goes from cold, to the middle, to almost in the red, then we get heat and it settles back down to the normal range. Last year we had a new water pump put in (due to the same issue) and the system flushed, although that only partly fixed it, and only for a couple months.

I am thinking maybe stuck thermostat and/or air in the system, but I wanted to get some opinions before hammering away at it. Thanks in advance!

I am surprised this 3yr old vehicle has coolant issues.
what is the coolant used exactly. who maintains the coolant ?