Has the block been checked to be sure there are no low spots that might leak a little coolant under the head gasket? I always check with a long straight edge and a feeler gauge, and if there's more than a .002" low spot anywhere, the top of the block gets decked. Ditto for cylinder heads.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!