Cooling fan quit working
 

Taking my Grandson for a ride in the country when I came to a long light where traffic was detoured. Coupla minutes while stopped,top down, I saw smoke escape hood over battery area and immediately thought,electrical fire. Didn't smell like it though, so I got over off the street and popped the hood. Coolant had bubbled out of the coolant tank and dripped on the exhaust making the steam.
Turns out cooling fan bit the dust. Still had fluid in my tank so I turned for home and made it just fine. Temp gauge never read hot.
Good thing I run an Unpressurized system,with my cap loose(I run 65/35 ratio to deter boiling), or Ida probably never seen any steam until I had blown something or seriously overheated.
101K on the car. Got the fan ordered for Tuesday. I'll let you know if that is all that is amiss. 135 bucks for Oreillys lifetime assembly.

Are you positive that the cooling fan is not running? The most common problem with the 4.0 and coolant is the plastic thermostat housing breaks and it leaks.

Thanks. Yeah,I got it home, started er up, turned on the AC max and it didn't come on. Reached into the housing and as soon as I gave it a whirl,it started right up. I hadn't noticed the fan running on low speed ever, but it kicked on high just fine til then. I checked fuse 3 and relays 25 and 28 which were okay in the box under the hood.

A former Ford dealer mechanic friend of mine came over to use my lift. The Mustang was sitting on the lift area,so he asked about it. I told him about the fan,the new one ready to install was in the trunk.
He installed it very nicely and it now has low speed and works well.