My 90 is losing water somewhere to the point that the reservoir must
be topped off every few weeks. I thought I had a water pump going bad
but I recently noticed a lot of white smoke on startup and until the
engine is good and hot, The car idles rough. Even when it's warmed up,
the car runs a bit rough (with the engine revving free, it seems OK
under load but a little lumpy at low speeds).

I guess this means that I may have a cracked head or a head gasket
problem, since I can't account for the water loss on the outside of
the car.  I have't noticed any gunk in the coolant, though.

What can I do to verify the head situation?  I have a standard
compression tester but I don't think it has the reach to get down into
a vanagon head.

Jim