We have a 2008 Sky bought original with 53K miles. In 2010, we parked the Sky in my work underground garage and leased a car as we didn't want to put many miles on the Sky as it's my wife's car and she and I want to keep it forever (or close!). Well, I covered it and every two to three months, I uncovered it and drove it 15/20 miles or so to exercise it. After three years of this, one hot summer day with the a/c on, the temp went to 245/50. I took it to the dealer who said the radiator system developed a bubble so they jacked the car up on one side and drained the system and flushed it. It was under warranty so no big bill. Fast forward to now. We drive it about every two to three weeks but last winter didn't drive it for two months or so during inclement weather. Today, after driving with the a/c on and going slow bumper to bumper for ten minutes, the temp shot up to 248/50. I turned the heater on full blast and drove the 20 miles home. The temp went slowly down to 189 so I turned the heat off and turned the a/c back on for the last 20 minutes home and the temps were normal at 194 to 205. Another bubble maybe? Your thoughts? I will start in tomorrow and let the a/c run at idle and see after 15 minutes or so if the temp starts climbing.