In this paper, we have focused on defects in aluminum radiator core. Radiator is simple air cooler function is eliminating excess heat from the engine radiator is used in a turbo engine for cooling purpose. Radiator is made up of core assembly, a tube, fin, cover channel(CC) and a header plate(HP). The core is made up of aluminum with clad material. During the manufacturing by brazing a process is one kind of welding processes after lots of defects are encountered leads to the leakage of radiator core. The header and a tube joint problem to check out of a dry and wet leak test machine. The study based on the aluminum alloy of radiator core defects and leakages testing a machine.