Good morning Aveo forum, new participant here. Just bought my first 2010 Aveo sedan Lt. 84500 miles on it. Bought it from a co-worker who recently had issues with the overflow tank cap, it suddenly blew off the tank while driving down the road. He refilled and replaced the cap. He also has had the head gasket replaced and head resurfaced along with replacing the timing belt from a previous incident. I drive 43 miles to work, morning till afternoon. While driving with the heater on, i get cold air then hot air. I have bled the system with cap off. I also have hooked my diagnostic scanner to it while driving to view live data. The coolant temps will range from 185 to 240 constantly, back and forth. This is why, im guesing, as to the fluctuating heat issue. T-stat opens then closes. Also, while parked and running, it will stay at a constant 203 to 206. To my knowledge the t-stat has not been replaced and has the plastic base still. Do you recommend i replace the t-stat? If so should i go with the updated metal base? Any help appreciated and glad to be a member. Thanks for reading.