I have an 84 Vanagon.  Today while driving I noticed in my rearview mirror
smoke coming out of my rear vents.  The engine seemed to run and sound
fine.  The temp gauge read normal ( although I'm not sure it works right
anyway). The electric fan was running up front. I went immediately home (
about 1/2 mile and shut it off).  I went to open the engine compartment and
could hear the coolant boiling.  All belts are inplace and seem tight.  The
coolant bottle is split at the seam and steam was coming out ( guess from
built up pressure).  Any ideas from the list would be helpful.  Thanks,
Jeff