I recently drained and flushed my cooling system on my 85 Westy.  I
     I drained and flushed it four times to get out all the coolant; so,
     there is only residual water left in the system. However, after
     draining the system per the Bentley method, I could only drain about
     half (10 quarts) the system capacity listed in the back of Bentley for
     this cooling system (18.6 quarts).
       My dilemma is, when I go to replace the antifreeze do I assume there
     is half of the water trapped in the system.  If so, I should add only
     antifreeze to get the 50/50 coolant mixture I desire.  Have others
     experienced this phenomenon?

     TIA,

     Vince.