Radiator Fan Clutch
 

I recently changed my auxiliary fans and the thermostat on my 1997 E420, but it continues to run hot while idling. My main radiator fan appears to be shutting off. I removed the fan clutch and cleaned it, but the problem still exist. When is the fan clutch supposed cycle on and off ? I would think that it should not shut off when the engine is running hot. I've checked the radiator cap and water pump and cannot think of anything else that would make it only run hot while idling. The engine runs cool on the open road. Any feed back with regards to the main fan clutch would be appreciated.