Finally, back underneath to find the old drops on the cross tube and there was the tell-tale residue of evaporated coolant on the intake to the coolant pump (Green arrow). Shut things down. Found the longest screwdriver I had and was able to reach the clamp on the hose to tighten it about half a turn. That seems to have taken care of it. I'll know more the next time at the hanger when I'll make a test run for leaks before I try to fly.