My 1998 DT466e runs 198-204, mostly around 200F. If you hit 210 for more than a few seconds without the fan clutch locking-up hard, something is wrong. By 215 you need to shut down because you are about to damage some expensive parts. Hit 220 and its game over.
Key point: THE FACTORY GAUGES CAN LIE. A ScanGauge D saved my butt when the fan clutch failed. The factory gauge said 200, and the ScanGauge kept climbing. So I shut it down and dodged a bullet. Whew! Spend the $160 bucks for a ScanGauge!