stooooooopid added electric fans, do not belong on a 4x4. 300tdi do not like it hot, over heating is their biggest killer resulting in head and pistons melting with pistons picking up on the bore and trashing that with molten alloy crumpling the turbo blades so pretty much an economic write off. They usually just stop running and refuse to start and that the first time owner noticed anything was wrong, expanding coolant hoses and sending fountains of water out of the coolant bottle when crank the next signs.
If it still starts up and runs and sounds normally, no strange noises or vibrations, with no obvious consumption of coolant, instantly pressurised cooling system, oil in coolant, leaks, water in oil, burnt smells etc you seem to have got away with it. Definitely check it over carefully for heat damage signs - think about replacing coolant, engine, oil weakened hoses/bottle. Fit the viscous fan !