[Vwdiesel] 93 EuroVan diesel - speaking in tongues

[rOLf peCHUkas]

I think it's Portugese - when I start up now just an instant after 
chick-vroom there is a < bvshshhht > sound - like air pressure through 
a membrane, like an inflated bladder collapsing, like an automotive 
raspberry - anyone know what this is? I could swear it's a new 
phenomenon
vacuum pump filling? faulty seal leaking? what pressurizes immediately 
on startup? brakes?
thanks for any guesses you can throw my way
(sound only lasts @ 1/2 second, starts a fraction of a second after 
engine fires up)
-- 
Rolf
Cambridge, MA