My 1.9 (in my '85) has a tiny vacuum takeoff on the forward (as in front of
the van) side of the throttle body (a thin vacuum line tees into it). My
bus runs like crap if this line pops off, but it's possible it just makes
your van hiss.  It's not easy to see it when standing at the rear of the
engine bay unless I lean way forward over the top of the engine.

See also my previous post about checking the two screws that hold the
throttle body in place. There's a rubber gasket between the throttle body
and the air distributor, I guess that could create a hiss if it's
cracked/pinched/missing.

Good luck!

Tim

At 01:45 PM 6/22/2006 -0700, Mike Elliott wrote:
>Mellow Yellow has developed a hissing sound which seems to come from
>where the throttle body connects to the air distribution manifold. I
>heard the sound then localized it by listening around with a bit of
>garden hose in my ear.
>
>I can't tell if the hissing sound is normal, and I never noticed it
>before, or if it new. Spraying carb cleaner there does not change how
>the engine runs.
>
>--
>Mike "Rocket J Squirrel" Elliott
>71 Type 2: the Wonderbus
>84 Westfalia: Mellow Yellow ("The Electrical Banana")
>74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
>KG6RCR