On a 2003 Cooper, does anyone know which of the two heater hoses is the inlet to the heater, top or bottom one? The top hose has the bleed screw fitting.

 

If logic prevails the lower line would be the feed, and top would be return.

The lower line, comes off the waterpump, feeds to the heater core, then out the top hose to the thermostat housing, where it is either circulated through the engine again or through the radiator.