I have a 2006 Lincoln LS. I've had issues with the coolant system/overheating since i got the car (almost). I finally got the leaks to stop but the car keeps overheating. It doesnt over heat to the point qhere the needle goes all the way to red and it cools off relatively quick (within 1-2 minutes). Also, it only heats up when i drive it hard or when im driving at highway speeds for a period of time. Regular city driving is fine. A couple hard pulls its fine. Also, i had the thermostat, coolant reservoir, hoses, and water pump fixed. I also flushed the system. Im not sure what could be causing the car to overheat. Maybe a head gasket? Radiator was fine last it was checked (past couple months). I had a trusted master mechanic perform most of the work as well as look over then entire system. Any help/advice will be appreciated. Thank you. Edit: the car will overheat all the way if i keep driving it hard. I usually turn the heat on max and chill out to get the car to cool down. The needle usually only moves a couple millimeters when heating up but on occasion is does heat up a bit more. And yes, there is sufficient coolant in the system. Ive also tried bleeding the system so at least most of the time i know theres no air trapped in the system. I will add there is a bit more water in the system than coolant. Maybe 70:30 water to coolant ratio. Thats jus because i needed to put something in there unless i wanted to be stuck on the side of the road due to a coolant leak thats fixed now.