Depending on the pressure rating of the cap the coolant won't boil at 104, it'll be more like 120 because it's a pressurized system.
That said, the temperature should really be sitting just above the temperature rating of the stat, and should not fluctuate that much. My 200 has no fan, that sit's at about 95 C no matter how hard I push it up the motorway, even towing. Now I know the TDi's are well known for being overcooled and the FL being a more modern car will be designed more around an efficient rad and less spare capacity, but other conventional car's I've driven which are built on the same kind of system, do not fluctuate that much.
The fact that the temperature gauge on the dash didn't move however makes me wonder......