 2003 Taurus overheating
I am having overheating problem with a 2003 Taurus (160k). It’s a little strange but it only seems to overheat on the highway. But will occasional overheat driving around town with the a/c on. Today driving around town for about and hour no issue. I got onto the highway (not using a/c) and the temp climbed. I would have to turn the heat on about every 15 minutes to cool it down, and then it would slowly rise agian. After driving for about and hour like this I got of the highway and slowed my speed down and the temp stayed in the normal range. I have had it at 4 different mechanics and no one seems to be able to fix it. The system had been flushed twice and thermostat replaced twice. The water pump also replace and system pressure checked. Radiator seems to have good flow. The alternator was replaced because the Ford dealer did not believe the electric fan was coming up to high enough speed. After all this it’s still overheating
Any idea?? | 
