This may sound  goofy, but with Green coolant I have NO leaks, with the VW orange
coolant, I get seepage at most joints and even around the head gaskets.  So I
switched back to Green coolant and I change it every year.  Try that?????

You say that:  "I took the cap off and could see the air bubbles coming through out
the hose up the tank at idle."   I do not see BUBBLES, just see coolant streaming in
the (left) expansion/reservoir tank.  m2cw  Malcolm