So all day yesterday my coolant system on the G6 was acting up... bad. On my second delivery I noticed some orange soda under my front tire so I popped the hood. Yup, Dex-Cool just gushing out from what looked like the bottom of the coolant recovery tank. This is on the drivers side firewall and is the highest point of the cooling system. It is also where the radiator cap is and is the only place to add coolant. Somehow it was FULL and bubbling as it gushed out of what looked like the bottom. Once it emptied out the reservoir on its own I could continue to drive it and I could watch the temp rise to the point of the thermostat opening and it would drop and hold temp.
Today I drove the car and it was doing the same thing... getting hot, opening the thermostat, then dropping to normal temp and holding until I would sit still. So I let the car cool. I then removed the thin upper vent hose then the two 10mm nuts. I then removed the lower main coolant hose on the reservoir. I cleaned and filled the tank 4 times and saw no obvious leaks. I checked the nipples where the hoses attach and no cracks. I see no cracks or damage ANYWHERE on the tank. I inspect the cap, it looks fine as well but just to be safe, I priced another. I inspected the two hoses that go into the tank. No damage, no soft rubber, no cracks or rips.
Upon inspection I gave it a dumbfounded thumbs up and put it all back together. I filled the tank to the cold fill line with DEX-Cool and it burped a few times so I re-filled to the line and it held steady. I put the cap back on and drove to the parts store. The cars temp rose to the normal mark and never moved off it the entire time I drove, stopped at lights, let it idle in the parts store parking lot, after I turned it off and went in for air freshener and came back out and started it back up. I then drove to the gas station, got gas, drove home and the whole time it didn't move. My Jeep was weird but this car may have it beat.
It pisses me off when things fix themselves and I am bereft of the pleasure of fixing it and having it work.