Upper coolant hose? Help me identify this hose.

[outrun]

Does anyone have any idea what this hose is for? I lost all coolant on the freeway and needed a tow. Is it a heater hose? It goes into the heater control valve.

 

[Number4]

It’s a heater hose and the plastic restrictor is known to break. A new one at Ford used to be under $20. Just reuse your spring hose clamps.