All this trigonometry sure is fun, but I can't help wondering if it is
really necessary to raise the  front of the van at all when
filling/bleeding the cooling system.
  I know what it says in the Bentley, but I have also seen posts from
those who say that they raise the *back*.
  It seems to me that if the thermostat is open and the engine is run at
a reasonable speed, the air is going to come to the bleeder screw at the
top of the radiator or emerge at the tank where you are topping it up.
  Of course follow-up bleeding at the radiator for a few days is
generally  wise.

Larry A.
91 GL (parked on a driveway at 10 degrees)