The radiator core is basically made of flattened aluminum tubes with aluminum strips that are zigzag in-between the tubes. These fins sends the heat in the tubes into the air stream to be carried away from the automobile. On each end of the radiator core is found a tank, usually made of plastic that covers the ends of the radiator,
On some modern radiators, the tubes go horizontally with the plastic tank on either side. On some other cars, the tubes are run vertically with the tank on the top and bottom. On older vehicles, however, the core was usually made of copper and the tanks were brass. The new aluminum-plastic system is somewhat more efficient, not to mention cheaper to produce. On the radiators with plastic end caps, there are gaskets between the aluminum core and the plastic tanks to seal the system and prevent the fluid from leaking out. On older copper and brass radiators, the tanks were brazed (awelding) in order to completely seal the radiator.
SEE MORE AT;http://www.automobileglobe.com/facts-about-the-radiator/