My 2000 Lincoln has 110,000 miles and has overheated 5 times in the last 30 days. I have taken it in all times and the mechanics cannot figure it out. It does not happen all the time. In other words when I take it in, it does not overheat, but after driving it a few days, boom, it happens again. The computer show nothing, the thermostat has been replaced, the lines have been bleed, radiator cleaned,,,and so on. Anyone have any ideas?