Tracer Product's TP-3900 Dye-Lite Coolant/Auto Body Dye quickly finds leaks in radiators, hoses, water pumps and fittings. Just add the dye to a cooling system and scan with an ultraviolet or blue light inspection lamp. The dye glows a bright green showing the exact location of all leaks. The dye will remain at the site of each and every leak. TP-3900 also pinpoints wind and water leaks. Just mix the dye in proper dilution with water, spray on suspect leak sites outside the vehicle and use an inspection lamp to check the inside of the vehicle for leaks.