It is better to add premixed anti-freeze.
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.
There is a water reservoir tank that goes to the radiator that you can add the water to.
To add water to the radiator on a new beetle, first remove the lower radiator hose. Then add water to the coolant reservoir.
If you are speaking of a radiator in an automobile, there is a plastic bottle on the side of the radiator, and it is marked for the fluid level; "ADD" or "FULL". The cap on the bottle will say "COOLANT ONLY" or words to that effect. Do not overfill. Older model vehicles you will add water to the radiator itself. Remove the radiator cap, slowly, and pour in the water. NEVER REMOVE THE RADIATOR CAP IF THE ENGINE HAS BEEN RUNNING! Wait until it cools down.
When a car is hot, keep the car running and add water to the radiator. When a car is cold, you can simply put the water into the radiator.
The answer is that if your water temperature is to high that is when your cars radiator is about to die.
You can add water to a radiator any time it is low on water.
Look for a radiator cap and add it there.Look for a radiator cap and add it there.
All cars that are water cooled (i.e. they have a radiator) must have a thermostat.
The most common reason for overheating of a car radiator is that there is not enough water in the radiator. Radiators can lose water in a variety of ways, and often need to be refilled. The other possibility is that the water is not being circulated properly. I should add that cars do heat up quite a bit in the sunlight on a hot day, which adds significantly to the chances of overheating the radiator.
Water alone is not used as coolant for automobiles.
Don't! Most cars have a reservoir for radiator coolant ... add liquid to the reservoir. Opening the radiator cap introduces air into the sealed system ... you don't want air bubbles in the cooling system.