[eagle]

When you bring it into a radiator shop make sure to tell them it is unpressurized. Model A radiators can be ruined if much pressure is used in testing.
Another thing, are you sure its leaking? Model As should be filled just to cover the tubes, as they don't have an overflow reservoir. When filling, if you splash a bit it can hang for a long time, won't evaporate like water. (if you're using antifreeze mix) Also, if its rusty, flush and change. When mixing coolant and water to put back in, use either distilled or RO (reverse osmosis) water, not tap water. Check the overflow tube, make sure it runs down the side and is soldered well.