Ed,

I think you hit the nail on the head.  It likely has a lot to do with how much squeeze-out one has on mating surfaces coated with RTV.  I recall seeing some blobs of Hylomar in my coolant after doing the rebuild on my 20B.  Hopefully, it isn’t plugging up the radiator.  A bore scope would be nice to have to look down inside my radiator to see if I’m fretting over nothing.  I would hate to waste a lot of effort reworking my cooling system only to have it turn out to be a partially plugged radiator (like Perry Mick’s experience).  As I see it, the radiator is serving as a filter for the cooling system. 

Mark S.