I have a junk yard thermostat housing that I have had for some time now but have not installed. There did not seem to be any difference between the one in the car and the one I picked up at the bone yard.
I noticed a symptom that became a clue. When driving normally, the temp would range from 155-170 but mostly at the lower end. Then, after sitting a stop light for 3 or so minutes, traffic would begin to move and I would run the escort through the gears to get up to speed. I noticed on many occaision that the temp would go as high as 190 and stabalize around there. With the sensor in the heater hose, any restriction to coolant flow could give a false reading on temp.
I looked at my bone yard housing and took notice of the port where the coolant flows to the heater hose. The coolant entrance in the housing is rather small and the thickness of the outlet pipe is thick, reducing the size of the coolant passage inside. I decided to try an experiment in modification.
I drilled out the outlet pipe to a size or two larger to allow more coolant to flow. At the coolant entrance in the housing, I smoothed and widened the opening to allow less resistance for coolant flow to pass through.
The bottom line is it seems to have improved the coolant flow because now my temp runs around 180 consistently. The engine is a little slow to get to operating temp but that seems to be the nature of this engine.
I would like to know how others have solved this problem. I am not sure that I am finished but the results are encouraging.