Mike,
You may want to research No-Rosion HyperKuhl Super Coolant. It contains anti-corrosion anti-electrolysis additives as well as the water wetter agents found in the No-Rosion product. If you do have a "pin-hole" in the aluminum that may be the cause. I use 2 bottles when filling my 5 gallon system. You can purchase it from Pantera Parts Connection. Something else, never use distilled water when filling the system. The purity of the water will leach minerals from your nice new aluminum radiator resulting in, you guessed it, a pin hole. I use bottled "purified drinking water with minerals added for taste" in a 60/40 (water/coolant) mix here is NorCal.
Steve
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