the only problem i know of with vanagons and winter is that the seal
between the engine and the oil cooler (that silver square box, just above
the oil filter) can crack in extreme cold ... and you can lose all your
engine oil in less than a minute! :(

here's the tech bulletin:

Technical Information
Group:    17
Number:   87-05
Date:     October 29, 1987
Subject:  Oil Cooler seal leaks in extreme cold
Model(s): Vanagon waterboxer, all Model Years

Extreme cold weather can harden and split the seal between the engine
block and the oil cooler thus creating an oil leak:
*  An improved cold-restistant seal was installed in production as of
   02/87.
*  The new seal can be identified by its silver-grey appearance and is
   available through your parts department, Part No. N 901 814.02.

joel