I bought my new radiator from The Brassworks, and I have to say, I’m very impressed.
Here’s the instructions that came with it for best results…
Do not leave your radiator in the box; install it, flush fluids through the radiator and polish brass as needed.
Radiators are constructed with solder and flux, a mildly corrosive acid. Each radiator is pressure tested in a test tank to assure there are no leaks and neutralize any flux used in the assembly. Leaving a radiator in a sealed box for a prolonged time may cause residual flux to oxidize. This oxidation may cause the polished brass to turn a light orange color and in extreme cases may “etch” the metal. This can be avoided by circulating fluids in the radiator and in the case of polished brass radiators, polishing the metal.
We recommend the use of distilled water to prevent premature mineral build-up in engines and radiators. Our customers often use a combination of 50/50 distilled water and ethyl glycol and report success. We are unaware of any long-term consequence to this common coolant.
New South Wales, Australia