Since we are talking radiators I would like to share my experience. We replaced our aluminum radiator in Kamloops, Canada a few years ago with a brass copper one. Last January while having the Thunder serviced a technician noticed what appeared to be a small leak. After removing the transmission cooler it was confirmed that our 5 year old radiator was leaking at the soldered tie ins to the tank. When pressure tested at the radiator shop it confirmed so many bad places that it was recommended that we re-core the radiator. When I inquired as to what would cause this to happen in a 5 year old radiator the answer was it was happening from the inside out and the coolant should have been checked annually and changed, as needed. This was CAT, extended life coolant. The problem was I did not buy the premixed jugs and they said that the tap water introduced minerals into the coolant that created the problem. So, after going through the expense of this repair again after only 5 years I highly recommend you check the coolant as part of your scheduled maintenance. This second repair was almost as painful as the first. The final outcome for everything, including removing and reinstalling the radiator was almost 10,000 dollars. Yes, I did have them use the premixed solution this time.
Best regards,
Larry Fisk