First post on this forum. Here's a preliminary summary: Car has been overheating for the last month Bleeding the air from the coolant fixes the problem for a week Coolant system pressure test and head pressure test reveals no leaks Coolant and oil look fine Replaced the primary thermostat Saturday and now overheats faster Constantly bleeding air out of the system Overheating is first followed by the heat going cold and the upper hose is hot while the lower hose is cold, even with the new thermostat I have a 2009 2.4 l that recently started overheating last month. Driving home and temperature light came on. Shut the car off immediately. Waited about 30 minutes and drove the car about three miles home with the heat on. The next day, drove the car and the temperature started to rise. Bought a new thermostat but before I did, I put the old one in a pot of hot water and it opened just fine. Bleed the air and the car was fine for a week. Began to overheat again, bleed the air, fine for a week again. Did this for about another week before getting it checked out. Took it to Pep Boys for a coolant pressure check. They checked the coolant system and head for leaks and found none. Oil and coolant also looked fine. Drove for another week and started overheating. Took it back to Pep Boys and they suggested replacing the thermostat. Went to the dealership and got the primary 170°. Replaced it this past weekend and everything was fine until. Monday on the way home, temp started to rise. Bled the system a total of 4 times since Sunday and still going up to 3/4 on the way home. Thinking that replacing the second thermostat may fix it. Any other suggestions?