Air Tightness Check

NOTE:

In case of defective operation, inspect the condition of the check valve and vacuum hose as well.
Replace them if faulty, and perform the test again.
If no improvement is observed, check precisely with gauges.

Start the engine, and idle it for 1 to 2 minutes, then turn it OFF.
Depress the brake pedal several times applying the normal pedal force.
NOTE: The pedal stroke should be the longest at the 1st depression, and it should become shorter at each successive depression.
If no change occurs in the pedal height when pressed, the vacuum booster assembly is faulty.

Courtesy of SUBARU OF AMERICA, INC.