[DAVEROX351]

Hi all.
I have a au ute series 1 6 cyl that starts overheating when I get up around 110kmh. Went into the red the other day so I turned aircon off backed off to 100 and temp went back to qtr. Did this on most slight rises on my trip. I recently had a new radiator installed, block flushed and new coolant added but is still heating up. Had thermo fans checked and they are working ok. Runs cool in traffic. Any ideas . Cheers