I have an 88 Westy and I occasionally have a leak in the cooling system,
but it's
from a rather odd place.

When you open the hatch to expose the engine, there is a small plastic tube
that runs
from about 12o'clock to about 6o'clock (going counterclockwise) just under
the edge of
the hatch opening.  There are several small tubes that feed up to this one
and
eventually empty into the expansion tank (that's not the one you fill).

On my van this plastic tube has sprung a couple of leaks and been patch by
PO and
by me with 'other tubing'  I occasionally get leaks from this tubing - just
enough to be
upsetting, but before I get around to doing anything about the leak, it
seems to fix
itself.  It normally leaks when it's been very hot.

I guess I'll eventually replace the tube.  I think that its purpose is to
bleed trapped air
from odd places in the engine.  Since part of my tubing is clear, I can see
coolant
flowing when the engine is on.

Good luck

John Graham
88 Westy
Charlotte NC