You have a blown head gasket.
Dexcool
radiator antifreeze coolant.
any vehicle that is water cooled and has a radiator needs antifreeze.
Intake gaskets have failed.
Find the source and repair it.
in the over flow tank
It is a heater hose.
Radiator or windshield washer tank.
It calls for dex-cool.
97 on up uses dex-cool coolant in its v6 engines
Dex-Cool
It is no longer necessary to add just water to a radiator in newer cars like the 2005 Malibu. An antifreeze that is half water and half antifreeze is usually best. Add the 50/50 antifreeze to the radiator overflow tank. It should be a plastic, see through tank hooked to the radiator.