I have a 96 GT w/ stock 4.6l 4.10 gears and a chip. I just had the coolant flushed about 5 months ago and is still on the full line. Within the last month with the raised tempatures my coolant light will come on with the engine temp being within the normal on the gauge. It only happens on the highway when above about 70mph. It turns off even when the temp gauge stays the same but going down to a lower speed. It has never hit the red warning mark or even close. Any ideas? Thanks!