hot under the bonnet d2

my disco 2 td5 decided to overheat today i have fitted a kenlowe fan but this did not cut in i beleive i had the sensor to high on rad not near rad outlet but have now moved it so hoping this will rectify it after refilling system it spat some out of expansion tank but this has now stopped so fingers crossed head gasket has not let go there are no tell tell signs of oil in water or visa versa so fingers crossed now thinking of fitting a manual switch for fan as do lots of towing and was towing heavy trailer when this happened any thoughts from you veteran landy owners

Try a thermostat first