I posted some Ford stuff in another thread but have a bit more to add. Yesterday on the way home I decided to test the overheating with no AC. Currently the fan does come on when the AC is on. Car will run up to close to A while sitting still. Fine while moving.
With no air...down the freeway no problem, sitting on R. Pull into the grocery store. And let it idle, no ac. Temp runs up to a high M, touching A. NO FAN COMES ON. I jiggle the connector, then remove the connector on the temp sensor (engine running). After a few seconds the fan comes on. OK so the sensor is doing something. I let the fan run and what happens, temp gauge comes back down to R. Nice. I get home and play some more. The AC clutch will not engauge while the temp connector is off. The Fan does come on when the ac is turned on and the temp connector is off. Also my check engine light came on.
So maybe I do have a blown head gasket, maybe not. but it seems these mustangs have a very poor cooling system. Maybe a possible cause for blowing head gaskets??? Who knows. I never saw any 2 speed fan action either. Still not sure what the difference in low and high is.
Oh as a side note I might have fixed the front cover leak. I took off the coil bracket and gave the 3 bolts on the right side a half turn of so. It looked dry under there yesterday. We'll see. Now if I stop losing water with that small leak I guess I have no head gaslet leak. At least it's not getting in the water.