Should be under the a/c evap on the passanger side under hood looks like a black ball
You can find Chevy Astro vacuum diagrams in several places, including online forums dedicated to Chevy vehicles, such as AstroSafari.com, and automotive repair websites like AutoZone or Haynes Manuals. Additionally, service manuals for the Chevy Astro, available through libraries or for purchase online, often contain detailed vacuum diagrams. You can also check YouTube for videos that may demonstrate the vacuum system layout.
try www.autozone.com
There are many gaskets and hoses that can leak. If you can't find it take it to a garage.
Which vacuum diagram The Underhood for the engine or the vacuum for the interior /AC system?
any library you can find it in a Haynes manual.
you can find it in a workshop manual
There should be a diagram pasted under the hood.
google images
I'm unable to display images directly, but you can find a vacuum hose diagram for a 1997 Astro Van in the vehicle's service manual or by searching online through automotive forums or repair websites. Many resources provide diagrams that illustrate the vacuum hose layout and connections. Alternatively, a local auto parts store may also have access to this information.
Haynes repair manual Chevrolet Impala SS, Caprice models 1991-1996 chapter 6
autozone.com has online manuals that have diagrams
find the vacume line and check for a leak in the system