Running warm condition

If combustion gas is causing air pockets in water jacket, where does gas go when I shut off motor? Does it flow back into combustion chamber?

I don’t think that would occur. The air (or gas) pocket if present would remain stuck at spots in the cooling system where it is prevented from rising due to the buoyant force and otherwise escape. Sort of like if a roller coaster got stuck at a valley in the track. Have you tried raising the front wheels and idle the engine with the radiator cap off? Usually if there are gas pockets forming, raising the wheels is enough to set some of them free, and you’ll see some burps at the top of the coolant inside the radiator as they escape. Note that seeing burps doesn’t necessarily imply there’s a head gasket leak, could be just a minor external cooling system leak is allowing air pockets to form. While you are set up for the above experiment, check to see if you see a bevy of small bubbles that get worse when you bump the rpm. If you see that phenomenon , that’s more likely caused by a faulty head gasket. But even seeing that isn’t definitive for a head gasket problem.

I have some electrical issues that come and go. 1 is the temp gauge reads below cold. And does not move during driving session. Next start, the gauge works. I assumed an air pocket might give odd readings? But the below “cold” mark on gauge seems like an electrical cluster issue and not a real temp issue.

I believe GM vehicles turn off the temperature gauge when a thermostat malfunction is detected as a nudge to get things checked.

See if the engine is reaching operating temperature, check for fault P0128.

I had 2 codes, 0118 and 0128. Too cold and too hot. I replaced thermostat long ago. Codes went away. When I say cold I mean needle is below 1st mark on dial. It does not read cool, it is off the dial. Next day it works. I replaced cluster as tach was reading 8000 rpm. Sometimes.

Oh well, kids equinox took a dump. Air in cooling system. Upper rad hose cold. Gurgle in heater core. Sis drove it for 10 yrs. no issues. Looks like a bit of crud in head cooling passages. Bled system wed. Did it again today. So, I pulled front head this afternoon. Do rear head tomorrow. Life is interesting.