86 stang overheating

[democrazy17]

Hi there I have an 86 Mustang 6 cylinder that overheats on the highway, if I am only driving in the city no problem never goes over half but on highway it will redline, I put in a new 160 degree thermostat just to see no change any ideas?

[Blue)(Fusion]

How's the coolant look? Is it full of rust? You should consider flushing it if you didn't when you changed the t-stat. If it's clean, than it may be a an air pocket in the top of the engine where the sensor is located, or a lack of flow through the radiator or other orifice.

Also check your water pump, it may not be working very efficiently anymore at the lower RPMs at highway speeds.