The issue I'm having is the vehicle gets close to operating temperature, but not quite there, and it won't hold a temperature. Any time I drive slow or come to a stop, the temperature will drop down a bit, then rise again once I start driving. Also, the heat blow warm, then hot, then warm, then hot.
First thought I had was air in the system, since I recently repaired a hose connection with some faulty hose clamps. Bled the system, got a few bubbles, nothing crazy, still nothing.
Next, thought maybe a thermostat issue. Had put in a Stant brand thermostat a few months ago, (when having same issue), but nonetheless, decided worth a shot. Removed the Stant thermostat and purchased a Motorcraft thermostat, that should be OEM. Tested both in a pot of boiling water, both seem to work fine. Not stuck open, not stuck close, nothing.
Put Motorcraft thermostat in for just cause, re-bled system (a lot of air this time), and still no luck.
As I just mentioned, I did have this problem a while ago, and the thermostat didn't fix it then (but always worth a shot), it ended up being the temperature sending unit. I can't remember if it affected my heat or not. I just remember the gauge acting wonky like it is now.
Do you think it could be another temp sending unit? Or another possible issue? I wouldn't imagine the temp sending unit affecting my heat, and I would like to think it would send a CEL (even though it didn't last time either.)