White smoke coming from Exhaust only when idle and coolant loss If you run the car normally and not let it idle no coolant loss at all no white smoke Good power on engine?
Typically, white smoke is just water vapor. Water vapor is normal when the engine is cold. Water is produced when gasoline is burned. Gasoline is a chemical compound called a hydrocarbon and burning of hydrocarbons produce water (H2O) and carbon dioxide (CO2). When the exhaust line is cold, such as a cold morning, the exhaust is cooled quite a bit by the time it comes out the tailpipe, and the cooled water vapor in the exhaust turns to white "smoke" much the same as your breath is visible when it's cold out.
If your engine is loosing coolant when it idles, make sure the engine cooling fan is operating properly. If the engine isn't cooling properly when it's idling, the radiator will boil over and you'll loose coolant. Once you start moving, air will move over the radiator and the coolant will not boil over.
you may have a vacuum diaphragm allowing coolant to be sucked into engine such as heater control valve