2510 petrol Mule cooling system

Hi, we have just acquired a 1993 2510 Mule fitted with a FD620 liquid cooled V twin petrol engine. It had previous cooling system problems which we have hopefully corrected by replacing gaskets, water pump, thermostat and fan switch. It is difficult to re-fill the system with coolant, but we managed by filling from several places and bleeding etc. Does anyone have a service manual as I would be interested to know what the ‘Works’ procedure is? The engine runs well, warms up okay and hot water circulates around the system. I am assuming the vehicle is heavily dependent on the electric fan because when driving slowly ~ 10 mph around the estate, the engine will be producing heat and there won’t be much airflow through the small radiator and so the fan switch cuts in and runs the fan. This must be the case unless anyone can advise us otherwise? Thanks