Jim,
I think this is somewhat the location MASNAKA is referring to. It reads the ENGINE water temp. Many cars will use the Ford thermostat housing with a threaded insert in it. This too with sending unit mounted in place will read the engine temp. Many, including
all of mine have two temp. units in place with the second one, actually a set temperature setting after the thermorstat, (usually on the side of the radiator) which I hook up to the fan, will turn the fan on automatically.
DV
PS, sorry it's a little fuzzy, too dammm early to set up the tripod!