I was driving to downtown and was stuck in stop/go traffic for about 10mins, not long. Then a mile later, the heat gauge went up to 270 and the warning message came on. Before I got a chance to pull over the Reduce Engine Message came on and I just pulled over and shut it down. I didn't notive Either Fan running but they both turn freely by hand with engine off, so no stuck debris. I just cleaned the radiator fan cage a month ago with air hose, only a few leaves, thats it. After shutting off the engine, I waited a few minutes then open the radiator or surge tank cap....slowly....and fluid started coming out and puking out the cap. Both Rad Hoses were HOT and Full. Last week the Drivers Door buttons would Not work and I had to shut it off, press reset a few times, open/close the driver door a few times, then all started working again. Not sure if that would have anything to do with OverHeating. I've read a lot of threads here and most say to Check the Fuses and Relays, which I'll do tomorrow. Some say maybe a air lock, could that happen without disturbing the Coolant system?? Oh, its a 2002 C5 with 29K miles on it and never been run hard. In the old days, it was either the Thermostat or Plugged Radiator. Any thoughts or suggestions would be greatly appreciated. ...Rocket

 

Sounds like your fans never turned on so I would start there. They should run with the A/C on, which if they don't, then you know you likely have an issue with them getting power.

 

Likewise..with only 29000 its hard to think its anything serious.rad cap? Fuses?