I have an 08 Cobalt Sport 2.4L and my husband accidentally crushed the radiator (prior to this, it ran fine, no problems). There was an interlock device in it, so my husband had it towed to have it removed. A while after that he got a new radiator and fixed it. It fired up right away and drove fine, until he tried to turn it off. Even when the key was in the off position and removed, the car was still running. He disconnected the battery and still it was running! What the heck could be the problem???