I have a 2004 mini hatch cooper petrol. The heater blower will only blow cold air when the engine is hot and the heater blower motor is switched on. I have topped up the fluid reservoir which was empty and bled the two air valves in the heater pipes but still blows cold air. The two pipes going into the heater unit are hot when the engine reaches temperature and if I squeeze one of the pipes the heater blows hot air again until I stop the engine. When I restart the engine the heater blows cold again. Also, since this fault, the temperature gauge goes to half way when I have only driven about 2 miles. Any ideas anyone. Thanks in anticipation

 

Clogged heater core. 64111497527

Heater Core Replacement - Page 2 - North American Motoring