I haven't had this car very long but it's never given me any issues. Last Sunday I went to the beach with a friend and my car randomly starting making a warning noise, like when your door is open. I couldn't figure out what it was, since my doors were shut and our seat buckles were on. A few more minutes into driving and the Cold AC stopped blowing cold. It blew Hot, but wouldn't blow cold. We let the car sit for maybe 2 hours before driving it again and we tested the AC. It blew cold. I continued to drive the car the next day. After about a 20 minute drive with it, it made the warning noise again. I looked under the hood and it had some small white smoke coming from the coolant. So We checked the radiator and discovered it had a leak. I replaced the radiator, put everything back together, and the warning noise still came on after maybe 5 minutes. Looking at the temp gauge, I could see it was overheating. So we tried adding more coolant ( yes we do water and coolant mixed) still didnt work. We checked the thermostat. It Is opening. We attempted to get the air out while adding coolant by putting the car on a slight incline, and squeezing the tubes as we put in coolant. I have NO idea what to do now. Can anyone please help me????