Something is not right, my 240D was running at 80C today within 5 minutes (with about 20-25F outside temperature). When the engine is as warm as it gets, can you feel hot/warm coolant going to the radiator? The radiator and the upper hose should stay cold until the thermostat opens at 80C. If you are getting flow to the radiator at less than 80C it pretty much has to be a problem with the thermostat opening too soon. If the thermostat is working correctly, blocking the radiator, removing the fan, etc. should no make any difference anyway. I would be tempted to replace the thermostat again (with an 80C OEM) just to make sure. I just can't think of anything else that would cause this. Anyone?