Since water cooled engines can overheat due to
air pockets at the thermostat, you want to know
before the engine heat causes boiling of the coolant.
First: Always know if your thermostat has a small bleed
thru-hole in it.
Second: Hook up a gauge to monitor temperature. The
wet bulb of the sender should be located in an area
sure to always have the presence of coolant, but in
an area that is the most hot. You can use a thermal
imaging gun to know for sure, but a safe bet is probably
the entrance to your water pump (especially on V-8 and V-6
Third: If you do not want to run your electric fans continuously,
locate the thermal switch for the fan relay directly on
or near the radiator. If it is a wet blub sender, TIG weld or
braze a boss right on the side of the radiator at the thickest
wall. If it is a dry switch do not drill into the radiator to mount
it, but rather mount the switch to a small metal plate and then
nylon tie that metal plate to the front of the radiator. A shroud
around the sensor is probably a good idea.