There are three common causes of radiator failure that can result in fluid leaks that lead to critical engine overheating.
A stone or other road debris thrown up can penetrate the radiator causing a leak. Replacement of the radiator is usually the only reliable, long-term remedy in this case.
Corrosion in radiators usually occurs as the result of an incorrect concentration of additive in the coolant water, or if no additive is present in the coolant. Corrosion can affect any part of the radiator, but it most commonly occurs in the areas where the plastic reservoirs are crimped onto the aluminium core. In most instances of corrosion, the damage cannot be repaired reliably, and the radiator must be replaced.
If radiator mounting brackets/rubbers/bushings are worn, damaged or broken, the radiator can be subjected to excessive levels of vibration. Over time the vibrations can cause fluid leaks between the plastic reservoirs and the aluminium core. Again, the remedy for this is to replace the radiator.