Pontiac G6 V6 overheating

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.

The thermostat is a cheap and easy item to replace and it is a common culprit in overheating issues. You also know that you have a radiator that leaks coolant. This can be much more of a problem than you might be aware. When coolant leaks out…and you then add more later, Air pockets can and will develop within the system…whether they be in the Heads or block or what have you. When this occurs many bad things can happen the pocket can get near the water circulation pump and render it Useless…instead of the impeller being submerged in coolant…it is spinning in AIR…which does NADA for the cooling of the engine. Sometimes cooling systems in cars actually have an air bleed nipple…Hondas are famous for this little device…and it gets used an awful lot when you fill those cooling systems.

I would remove the thermostat and replace it…while you have it out…pour coolant into the hole left behind when you removed the T Stat…this will go a long way in removing an air pocket. If you do NOT have an air bleed nipple the ONLY way to remove any pockets of air is to fill the rad…and the reservoir and then take the engine through SEVERAL Hot Cold Cycles…this will allow the fluid to get hot and expand and overflow…then cool and pull in coolant from the res…this “Burps” the system over time. On top of all this…and in fact I almost forgot…NONE of the Burping process will work with a break in the system…it needs to be closed…SO the cracked and leaking rad needs to go along with the T Stat. So…replace the Rad…Replace the T Stat…and then Burp the system…Until you replace the rad and close the system…it will remain open via the crack in the Rad…and there will be no way to remove any air pockets in the system.


I recently had to replace a leaky water pump on my wife’s 09 G6 with the 3.5 V6. I ended up with a stubborn air pocket in the area of the water pump. I ended up having to pull the radiator hose off the casting just above the water pump. I then poured coolant into the hose which filled the radiator and into the casting where the hose attaches. That cured the problem. To get at the hose you have to detach the air intake duct and swing it out of the way - very easy.

I really urge you to replace the radiator ASAP to avoid overheating damage to the engine. Hopefully it hasn’t happened already.

Edit: I really doubt you have a water pump or thermostat problem. Air pockets on today’s engines can really be a pain even though the reservoir is full and sits high on this car. You have to get creative.

http://www.tooltopia.com/uview-550500int.aspx I have had good luck with a coolant fill system like this one to prevent air pockets.

i have no plans of driving, or even starting the car until the radiator is fixed and finding out why the check engine light is staying on. going to the shop tomorrow and will post an update. thanks for the feedback

Good plan to focus on fixing the radiator problem first. A leaky radiator causes more problems than just having to refill it once in a while. It also causes the cooling system to not be able to achieve the pressure the car designer engineers intended it to operate at, which it needs to achieve the cooling capacity needed for the engine to operate without damaging heat sensitive parts.

Heard back from the shop, aside from the radiator it just needs a waterpump and thermostat. knocks wood. So far they haven’t found any signs of engine damage, will have to wait until the repairs are done to say for sure.

Just my two cents but that car has Dexcool in it. Any air introduced into the system can cause gunk to build up and block the cooling. This is not the old days when you could just ignore a coolant leak. I think you need to get it to a shop where they can flush the system and determine if there are passages blocked, replace the radiator and thermostat. I think the radiator also comes out the bottom so not really a DIY job anymore.

Hmmm…Almost exactly as I guessed it. I dont see any reason for the new water pump however…How’d that come into the picture? For fun I guess? I’d approve everything BUT the new pump. That sounds like a classic case of “Padding” the bill to me. Theres nothing to suggest the pump is an issue AT ALL. Just my Professional Opinion. Perhaps there was some clue that I am not privy to…which is certainly possible…but Honestly I think a new pump is total BS.