Same car; takes for ever to heat up for precisely the reason FordMan59 mentioned. Could take a two hour highway trip, get out and hold my hand on the engine. Needle in this weather rarely reaches the "N" in normal. (even after 30 minutes of driving) In my case, heater output is directly tied to engine temperature. When the engine gets warm, so does the heat.
The vehicle hasn't been overheated yet the bypass valve very gradually opened over the course of several years.
I haven't fixed it because of the headgasket problems associated with having an aluminum head atop an iron block. The aluminum head expands 1-3 times faster than the iron block. This can cause the headgasket to leak. I've replaced it once at 190k. Should've replaced it well before then. (was just forced to then)