Technical Punto S overheating puzzle help please

[Calibre1]

Hi. Symptoms: Temp gauge goes into red. Fan does not come on. The fan works if connected directly. New fan switch fitted and works.
As car warms up and gauge climbs, the top hose gets hot, bottom hose stays cold unless heater is on when the heater hoses get hot and bottom hose warms up. Radiator gets hottish at top and cooler at base. System bled. As temp gets near red, coolant level rises in the filler tank and squirts out but is cold. Any ideas what is wrong? All advice appreciated.

 

[Ffoxy]

Possibly an air lock created by a small gas leak from combustion chambers into the coolant system... in other words a possible Head gasket issue.

 

[MadMan0]

thermostat issue mabey?

 

[DaveMcT]

Could be & coolant pump may not be pumping and the pressure overflow suggests the head gasket has failed. Cylinder compression tests and see if the coolant has exhaust gasses in it may help prove it.