Cut the actual mechanical part of the thermostat out, leave the shiny metal frame in because it acts as a washer to seal the housing; it allows there to be no restriction in coolant flow. Also direct wire the fan ( not just on more often=all the time )to the rear daylight power side of the rear break light-it is a dual filement bulb. It draws very little energy but it´s best to take less power from the daylight running or high beam because the actual breaking or high beam is more important. If that don´t work see if oil has coolant in it and make sure there is no calcium build up clogging the pipes .