Ultraviolet Light Method
A leak detection additive that is added to the cooling system is available through the parts department. The additive is highly visible under ultraviolet light (black light) (1). Pour one ounce of additive into cooling system. Place the heater control unit in the HEAT position. Start and operate the engine until the radiator upper hose is warm to the touch. Aim the commercially available black light tool at components to be checked. If leaks are present, the black light will cause the additive to glow a bright green color.
The black light can be used in conjunction with a pressure tester to determine if any external leaks exist.