[700rpm]

Try just plain water, not a coolant. Water cools better. High temps can cause water to overflow and present as a leak. Model A radiators like to find their own fill level too. Also, make sure you are timed properly and driving the car with the spark lever about half way downmto avoid overheating. Lots of things can look like leaks in hot weather when sometimes it’s just water overflowing out the overflow tube.

Radiator problems can take the fun out of owning and driving a Model A. I have tried all kinds of shade tree tricks in fifty years of playing with these cars. The best fix I have found is new reproduction radiators. Yes, they are expensive, but to me, for reliability and peace of mind they are worth it.