Reply to "New Custom Radiator; need opinions"

The Corvette guys have been running aluminum radiators as well as engines and heads sine the '80s. One 'Vette shop says to take a GOOD VOM, switch it to the lowest current the meter will read, stick one probe in the coolant while grounding the other. If your meter reads above 70 millivolts, you have a problem. I tried this on our '72 with aluminum heads & water pump & Fluidyne rad. With a cheap VOM, the needle only flickered. With a $250 Fluke VOM, I got 37 millivolts- in safe zone.
Second game you can try is, once you succesfully get a reading, start switching on some electical stuff with it still connected to the coolant. If the meter reading changes, you have a grounding problem and it very likely won't be the radiator or its thermoswitches. You can start intelligently chasing a bad ground in your wiring, but at least you'll know which circuit(s) causing the problem. I've seen grounding problems so bad, the oil pressure reading changes on a running engine when the headlights are turned on!
Finally, use No-Rosion in your coolant if your local water is very hard. Adding distilled water is a mistake IMHO since distilled water is almost as acidic as Pepsi. Deionized (DI) water is better. Any doubts, get some pH strips from a swimming-pool supply house and check your local water and whats in your radiator for acidity (or lack of same). One East Coast guy DISSOLVED two Fluidynes (full warranty from a Pantera vendor) in a year, before Fluidyne figured out what the problem was. Good thing he didn't get his rad from Cheapo Mail-order, Inc....