Could be a cracked head or a blown head gasket.  Probably a cracked head since
the water is coming out of the exhaust port.  You should see some dripping
coolant coming from the where the exhaust flange meets the head nearest the
where the crack is.  If you can narrow down the source of the leak then you
might be able to get away with removing and inspecting/replacing one head
instead of both.
You should not drive your van until this is fixed as you will destroy your
motor.
Ken Wilford
Van-Again
John 3:16
PS I sell rebuilt heads for $250 plus shipping and an $80 core.