Fuller & Johnson used a few different cooling methods and fluids in their engines.  Enclosed circulation was used with either mineral oil or plain water.  Open circulation used just water.  And of course the celebrated Farm Pump engine as well as the light plant engines were air cooled.  A number of solutions were used to keep the water from freezing in cold weather.  Calcium chloride was the main one specified.  If this was used in the model K engines then the water feed was not to be turned on.  The later radiator cooled engines could have used either an alcohol or glycol based coolant.  A "straight mineral oil" was specified for the oil cooled engines.  Today a modern heat transfer oil is both highly recommended and effective in these engines.  F&J always instructed the end user to keep the water passages clear from lime, scale, mud and debris.  Any buildup on the iron surfaces would act as an insulator and impede the transfer of heat to the cooling solution.  A heavy buildup of mud, chaff or sawdust could completely block a cooling passage creating a localized hot spot.  Worse still is that such material retains water and can cause freeze damage even thought the cooling system was drained.  It was always emphasized that if calcium chloride or some other antifreeze solution was not used then DRAIN THE WATER IN FREEZING WEATHER!  Even a light frost could cause damage.  The model K even had a drain provided for the water injection system.