With regards to temperature, diesels are opposite of gasonline engines. It is not uncommon for diesels to cool down at a red light, particularly in very cold conditions. New Volkswagen TDI diesels do this as well. Diesels also like to run hot. Diesels like to work.
Its my understanding that 603.960 engines rarely need water pumps.
My mechanic has an infrared temerature sensor so I will ask him to look it over. Its possible the thermostat is not working correctly (not opening fully?) so I will try changing that as well.