The coolant temperature is too high (over 110°C), the warning light comes on while driving
There is too little coolant in the circulation system
The expansion tank must be filled above the "M1N" mark. Check the cooling system for leaks
The thermostat does not open. The coolant circulates only in a small circuit
Check if the radiator outlet (lower) hose is hot. If not, remove and check the thermostat. Replace it if necessary.
The electric fan does not work
Check the fan plug connection and contacts for reliability. If necessary, run an auxiliary wire from the battery to the fan. Caution! Risk of injury from rotating fan. Check the thermal switch.
If all the listed components are normal, then the radiator is clogged. It should be replaced.
Source available here (PeugeotBook.ru)