Leaks from Radiators
Leaks caused by internal corrosion may be found almost anywhere on radiators. The most vulnerable points are usually the seams and where the tubes are joined to the headers. The underlying cause is almost always cooling system neglect, but it may also be due to bad ground connections between the engine, charging system and vehicle body. If the coolant has been changed regularly and tests good, check the engine’s ground connections and clean and retighten as needed.
Solder bloom is a type of internal corrosion that can form when neglected coolant, rust and some types of leak inhibitor additives react with the soldered joints in a copper/brass radiator. White to green crumbly deposits begin to grow, which can block tubes and restrict the flow of coolant. A radiator with this kind of problem must be recored or replaced. The cooling system should be cleaned and flushed to remove deposits and sediment.
Leaks caused by punctures in an otherwise health copper/brass radiator can usually be patched by soldering, brazing or even sealed with epoxy or specially-formulated high temperature hot-melt adhesive (which is not the same kind of adhesive used in a home hot glue gun). If the radiator is full of corrosion, though, a patch is not going to last. The radiator will have to be recored or replaced.