radiator cap might be leaking
Intake gaskets have failed.
when your engine is hot it causes the water to boil and the water and the anti freeze will come out of the overflow pipe.
On passenger side of the engine compartment, you'll see a see thru container with 3 small hoses coming out of it and a black cap. This is the coolant recovery tank and this is where you put antifreeze/coolant in.
If there is no leak visible so you can see antifreeze under the parked car, you probably have a head gasket going bad. You may have some signs of steam in your exhaust, or at least a sweet smell coming from the exhaust. You should have a compression test done on your engine. That is exactly what the overflow reservoir is for. When the engine is hot, excess coolant goes into the overflow tank, as the engine cools,it draws coolant back into the radiator.
To the overflow tank and if the radiator has a cap,you will need to fill it with the engine cold.
In the overflow tank as well as the radiator. You should not do this while the engine is HOT!
With the hood open, on the passenger side there is the overflow container for the rad. The cap might be pressurized if the engine is hot. You add the antifreeze there.
Engine overheating will cause the anti-freeze to surge into the overflow tank. A blown head gasket will also cause the anti-freeze to surge into the overflow tank.
You really do not need to. Put the cap on and run the engine, the excess will flow into the overflow canister.
Look on the side of the coolant overflow bottle. There should be a low mark for the coolant for a cool engine, and one for a hot engine.
look for antifreeze coming out of the radiator as the engine warms up after a cold start.
Heat from the engine causes liquid to expand. It used to overflow onto the ground if it caused enough pressure to open the radiator cap. The overflow tanks were installed to automatically catch and return the coolant to the cooling system.