Hi, I would have thought there is already a fan on the BN which is thermostat controlled ,so I would presume it is all working within its perimeters set by the factory . If the temp gauge is sitting in the red then you have an issue and continued use in the red will damage the engine in time . Firstly if it was me I would tell the dealer to sort it ,however you state the dealer can not resolve . That's not good enough IMHO . If it was out of warranty I would suggest you remove the thermostat completely which should keep the top temp a bit lower as long as you have not got another issue ie the water pump or a kinked hose causing a lesser flow rate .