In Reply to: How do you test with a vacuum pump? posted by JohnL '75 02 (Golf) on March 08, 2000 at 10:22:24:
Just get a vacuum pump and a suitable grommet to jam in the hole, stick the v.p. line in there, and try to draw a vacuum. If it holds a vacuum, its good. If not, its bad. Also check the one-way valve in the line. If the car runs, you can just run it, shut it down, and then pull the line from the booster - if its good there will be vacuum in there that will loudly relieve itself when you pull the line.