[31Tudor]

I am certainly not a radiator expert by any means so sorry to cause confusion. My thought was if water is restricted from flowing through many of the tubes in the radiator, it would then reduce the transfer of heat through the fins, thus allowing the engine to run hotter, therefore allowing the water to expand more, and then as it expanded it would go through the overflow. And what Katy said sounds good! Kind of like a funnel, doesn't make any difference how much you pour in, it can only go through the bottom of the funnel at a certain rate.