Check Air Tightness

Start engine.
Stop engine after running for 1 - 2 minutes.
Depress brake pedal several times with the same load as in ordinary braking and observe pedal travel. If pedal goes down deep the first time but its travel decreases as it is depressed the second and more times, air tightness is obtained.

Fig 1: Checking Booster Operation For Air Tightness
Courtesy of SUZUKI OF AMERICA CORP.
If pedal travel does not change, air tightness isn't obtained.
NOTE: If defective, inspect vacuum lines and sealing parts, and replace any faulty part. When this has been done, repeat the entire test.

Fig 2: Checking Booster Operation For Pedal Travel
Courtesy of SUZUKI OF AMERICA CORP.