coolant leak / coolant seal leak
If you smell something sweet or coolant smell, you may have a coolant leak or if the smell is accompanied by a thick white smoke from your exhaust that doesn't go away, you have a leaking engine coolant seal.
If you find the leak to come from the radiator or hoses, simply replace them.
If you have the second option with thick white smoke, you have a leaking engine coolant seal. To fix this one you have to rebuild your engine.