During these really cold winter nights I've noticed that the temperature barely gets to 90c. When driving casually the temp struggles to get to 70c especially when the heater is pumping air out. Uphills it will start to warm up quicker then going downhill it will begin to cool.
I'm happy that the thermostat and temp sender are all ok as motorway driving the engine gets hot. I'm really surprised how diesels can 'cool off' when not under load, unlike petrol engines. Even idling with the heater on the engine will cool. Does anybody else experience this or is there a problem? I've checked for water circulation and there doesn't appear to be any getting to the radiator, so all seems ok. It has to be cold though, 0c and colder. It's fine at say +5c.