will start with the back story, i have a 2007 G6 V6 that had a slow leak in the radiator. I kept it full and it only went higher than normal once but i noticed it right away and didnt let the needle peg at hot so i’ve kept it full, checking it everytime i went somewhere. the other day on my way to work the needle pegged at hot and the temp light came on so i pulled over right away and shut the car off and let it cool for an hour and added some more coolant. started it up again and the temp stayed normal for a minute so i tried to get it back to the house when the needle pegged, i lost power and the check engine light came on. i stopped the car and called a tow and while waiting on the tow truck my battery died and all i had running was the hazards. the only thing i noticed was the leak in the radiator had gotten worse. after i got it home and let it sit for 5-6 hours i got a jump from my neighbor and i noticed i wasnt getting any circulation, the resevoir was still full, the check engine light came on and stayed on, and within a minute or two the temp was rising fast so i shut it off and havent touched it since except to check the oil which looks, smells, and feels fine and is at the proper level and didnt see any oil floating around the overflow tank. and while the car was hot i didnt see any smoke or steam coming from anywhere aside from the leak in the radiator, the waterpump pulley was spinning fine, no whining or whirring sounds. i did notice that the plastic piece where the metal overflow line attaches to the engine was badly cracked but wasnt leaking.
i’m thinking maybe the waterpump went out and/or the thermostat is stuck closed and caused the overheating issue. as far as the check engine light goes, could that cracked plastic piece cause the check engine light to stay on?not sure if there’s a sensor involved in that or not. or could it be the low coolant sensor causing it as the block has no coolant in it?
any thoughts on the issue would be appreciated, thanks.