Radiator Flow Testing
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With the engine cold, fan removed, and radiator wet; watch the fins as the engine warms up to temperature. When the thermostat opens, fog will rise off the fins on flowing core tubes. Those that stay wet (at the bottom) are plugged. This one has none that stayed wet, so the radiator's coolant side is working perfectly. I've seen them with ~1/4 blocked internally still run without getting too hot.

But this does not test for AIR flow through the fins...

Owner caption July 2024 · Photo 0 of 5000