temp gauge needle goes into red on steady acceleration and drops back when off accelerator. If you continue to acccelerate when on red, yellow warning light comes on and then engine light and engine goes into "failsafe" mode presumably. (very rough and noisy with muc vibration). Once "cooled down" goes back to normal but to avoid going into red have to keep taking foot off accelerator so needle goes back to midway point. No obvious signs of overheating when you look under bonnet.
Thermostat and sensor have been replaced and radiator has been hosed through and new coolant added.
According to onboard diagnostics, engine runs at 104C when needle midway and 124C when in red. No fault codes showing. Any ideas please???