My wifes 2006 mountaineer V8 overheats. She says itll only do it sometimes after the truck has been warmed up. She will come top a stop and the temp will spike and she will get a warning light then it will go back to normal and be fine. When the temp spikes she hears a loud whooshing or whirling sound coming from the motor which I supposed is the fan? Could it be a bad thermostat or waterpump?

 

Have you worked on the cooling system lately where there could possibly be air in the system. Otherwise I would think possibly a fan controller not sure what they call it on your specific model but I have had them go out on mustangs in the past with similar symptoms