I recently had my 2007 chevy cobalt flushed by a Flynns Tire store as a maintenance procedure. The car had been running fine up to that point. I have never had any problem with the engine nor the radiator system. This was purely for maintenance purposes. 120 miles later while traveling to Ohio, a cooling down mode indication sentence came across an indication board on the dash board. I called the spokesperson for Flynns where I had the flush completed and asked him about the information being shown. He went to the mechanic who completed the flush and was told that it was probably a bubble in the system and that if the light went out it would not be a problem. Within 30 seconds of him telling me that, the light went out and the car continued to running fine. About 2 minutes after our conversation, the car shut down to the point where I had to drift it off the interstate. The car would not start. I called the Flynns dealership back after opening the hood of the car and indicated to him that there appeared to be antifreeze around the front of the engine and on the radiator dripping. I had Triple A tow the car to a Flynn's dealer in Ohio at his request stating that they would take care of the problem if it had anything to do with what they had done to the car. The car was towed to the dealer who indicated that the fluid had indeed emptied out of the car. As it turns out, the engine was destroyed in the process as I found out the next day. The spokesman from the PA store said that the Ohio store mechanic indicated to him that the radiator was cracked at the bottom which caused the leak and that they did not cause the crack. We discussed the fact that up to that morning and not until after they completed the flush, there had never been any indication of any leak anywhere in the system. The car had been inspected and maintained by this Irwin shop for the past four years. Please advise me.
Cracked radiators are nothing new. It happens on all car brands although it isn't real common. While I agree it's quite the coincidence, a cooling system flush should not cause a radiator problem. The fact you had no problem for 120 miles proves that. An air bubble in the system that prevented the thermostat from opening would have been noticed within a few minutes. One could also argue the problem was caused by putting gas in the car because that was also done shortly before the problem occurred.
It's hard to argue for or against the shop that did the work without seeing the car, but I'm pretty sure they are not to blame. In rare instances there can be sediment that has collected that is blocking a leak from a hole caused by corrosion. The flush is supposed to remove that sediment, but then a leak would either have shown up right away or as soon as normal system pressure started to build up.
The other thing you have going against you is GM's use of the red Dex-Cool antifreeze. We call it "Dex-Mud". You'll be fine if you get that stuff out every two years, not every three like GM recommends, but in the meantime acid builds up in the system. That can't be helped. Antifreeze is always going to be antifreeze, but we change it to get that acid out and because the additives in it wear out in about two years. If that antifreeze is left in too long, corroded and leaking heater cores are real common, more so than radiators, and replacement heater cores often corrode out again in less than a year. GM has had a lot of trouble with that on their trucks.
ON the other side of the story, it seems odd they would be telling you that you need a new engine. You would have had to have a real lot of warning before it got that bad. If you ignored the gauges, the lack of power, and the noises, the engine could be damaged, but we normally make repairs, not replace the whole thing. I think I'd get a second opinion as to why it quit running. There are a couple of sensors that are critical to engine operation that are known for failing by becoming heat-sensitive. They often work again once they cool down for a few hours. That is a far cry from needing a new engine.