>There is a whiteish plastic piece that appears to
>thread like a screw down into the heater near the on/off lever.  I found the
>top to this broken piece jiggling around on the floor.  Can it be as easy as
>replacing this piece?

That is the bleed screw for the rear heater core.  Mine broke similarly
on my 84 Westy back in the Spring of last year.  At that time I replaced
the heater core with a new one I had on hand.  I have since drilled out
and used a screw extractor to remove the remains of the bleed screw in
the "blown" heater core, and installed a new bleed screw and gasket, and
that heater core now resides in my 87 Syncro keeping us warm in all this
frigid weather lately.

Yes, the repair can be that simple IF it is only the bleed screw that has
failed and the core is not leaking.  Do use new gaskets between the
heater valve and core, and for the new bleed screw.  I purchased the
needed screw and gaskets for cheap at the Bus(ted) Depot.

Best wishes,

Tony

Anthony L. Mourkas
Hampden, Maine, USA
1984 Vanagon Westfalia
1987 Vanagon GL Syncro
1991 Jetta Eco Diesel