Okay thanks. I am wondering if the resistor pack on the fan is burnt out for the low speed ciruit. The resistor pack is used to drop the voltage to the fan for 'low speed' operation - this is the mode that runs first before the full speed circuit kicks in when needed.

The water pump on the Cooper S should always be engaged (unlike the cooper where it has an 'on demand' setup), so the water should always be circulating. The thermostat bypasses the radiator when cold and opens the radiator circuit when hot.

WM18179 
I've replaced the thermostat housing with oem, no adapter provided
Engine temp at 210, upper rad hose 180, lower 87,
purge tank starts to fill up, fan has not turned on.
I have not noticed any leaks.
Problem started while driving through wet slushy
roads, temp light came on and when I pulled over
purge tank boiled over.
Fan does come on periodically with the ac on.
Water pump maybe? How do I check that?
Thanks!
Kevin

Did this problem start all of a sudden 'out of the blue' or were there some changes made to the engine that prompted this problem?

Is the radiator hot when idling with the temp sensor plugged in? - to confirm thermostat is opening as the coolant heats up.

The signal from the thermostat temp sensor goes directly to the computer. Since the fan runs with the temp sensor unplugged, it sounds like the temp sensor is not sending the proper signal. 

Did you use an adapter cable when installing the new thermostat housing?

Can I get the last 7 digits of the vin number?

North America Motoring

No. The temp  sensor is in the thermostat housing.

Does your Countryman have the alloy 90 degree elbow in the upper radiator hose with the temp sensor on it?

OK, so no answers . Is there another forum that has more of a following i could go to?

Overheating, fan will not turn on
I've replaced with oem, coolant temp sendor,
both relays, thermostat housing.
Fan does come on with AC, and with diagnostic
reader, and will come on and stay on with coolant
temp sensor unplugged, so I assume the fan is good
The car has 40,000 miles.
Now......would a bad fan resistor prevent the fan
coming on?  Is their something I'm not familiar
with?
I can idle the car until it reaches about 207 degrees
and cooland will fill and overflow the tank.
Thanks for any suggestions
Kevin