What would cause this overheating?

[nightrider50]

This is on my daily car, not the mustang, but should work the same in theory.

Temperature guage is saying car is overheating, but the radiator and upper radiator hose are still ice cold. The radiator and overflow tank are full.

 

[f8tlfiveo]

Check thermostat.. Sounds like it's not opening..

 

[Chrome_Rust]

t-stat

 

[FoMoCo17]

Probably thermostat like already stated. Have you seen any fluid flowing in the radiator once it was warmed up. If not, thermostat again, replace. If it is flowing, possibly an air pocket in the motor causing it to heat up in areas and the gauge is reading it. Had it happen in mine but as soon as things moved about, the gauge would drop. If its continually goes to hot and stays there, definitely replace the thermostat.

Good luck!