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This could be caused by a couple of different things. A leak could exist in many components that hold the coolant , i.E. Radiator, water hose, thermostat housing, water pump. Check all of these components to ensure there are no cracks, leaks or loose connections. Worst case scenario would be a cracked head and / or head gasket. This would allow coolant to leak into the engine combustion chamber and be burnt out the exhaust (white smoke indicates water / coolant). This condition would normally cause poor performance of the vehicle though.
Although a low coolant level will not normally cause a hard start, it could be that the vehicle was driven with low coolant causing the engine to overheat. Then after parking and trying to restart, it would indeed have a hard time since it had overheated. With more coolant added back to the system, it cooled the engine back to normal operating temperature and allowed engine to crank normally.
Thursday, January 2nd, 2020 AT 8:12 PM