90 minute run at 75mph = cold radiator?

[Cooper Man]

I have a Jun 03 MCS that has covered 180k miles and is suffering the "slight loss of light-brown coolant from the header tank" problem ...and has been for a while, and gets topped-up regularly. So I am planning to flush the system and replace the coolant and cap, and possibly the thermostat and housing.
BUT, I was poking about under the bonnet today after an 80 mile drive and noted that the header tank was "hot", the radiator top and bottom hoses were "warm", but the radiator was cold, not even luke-warm!
I didn't even think about touching the block, but I suppose I should have done ...I can try that one later.
The car is performing well, no smoke/steam from the exhaust, no emulsion in the oil, no puddles on the floor, the air-con and heater work well, so I am a little bit confused.
I don't hear the fans come on that often, so the car isn't overheating as such, despite the slight loss from the header.
So I believe that there must be a blockage somewhere - could it be the thermostat failing to open/close?

[BJM]

Hot block and cold radiator is a common sign that the thermostat has failed.

My other half mini One has the coolant leak problem and this afternoon I've taken the Thermostat housing off as it appears to be leaking. It took me about an hour.

I'd say that if your going to be changing the housing then your silly not to do the thermostat at the same time. You can also do a kettle test to see for sure if the stat is gubbed.

What does your temp gauge say?

[Cooper Man]

Quote: Originally Posted by BJM (original)

What does your temp gauge say?

Temp gauge? What's that? My S has the OE satnav, so luxuries like a water temperature gauge were done away with by the designers.

I have fixed the problem ...by simply fitting a new cap to the header tank.

I've got a new thermostat and housing lined up, ready to be fitted once I have some reasonable gauges to fit a new instrument pod I have recently bought. A temp gauge is on the agenda, and considering how much stuff has to be removed to get to the sender unit/thermostat area, it'll all be done in one go.