Operation Check (With Gauges)

Connect gauges as shown in the figure. After bleeding air from pressure gauges, proceed to each check.

Fig 1: Checking With Gauges

Courtesy of SUBARU OF AMERICA, INC.

1. Start the engine and keep it running until a vacuum of 66.7 kPa (500 mmHg, 19.69 inHg) = point A is indicated on vacuum gauge. Do not depress the brake pedal.
   Fig 2: Checking Air Tightness

   Courtesy of SUBARU OF AMERICA, INC.
2. Stop the engine and watch the gauge. If the vacuum drop range is less than 3.3 kPa (25 mmHg, 0.98 inHg) within 15 seconds after stopping engine, the brake booster is functioning properly. If defective, the cause may be one of those listed below.

• Check valve malfunction
• Leak from vacuum hose
• Leak from the shell jointed portion or stud bolt welded portion
• Damaged diaphragm
• Leak from valve body seal and bearing portion
• Leak from plate and seal assembly portion
• Leak from poppet valve assembly portion

1. Start the engine and depress brake pedal with pedal force of 196 N (20 kgf, 44 lb). Keep the engine running until a vacuum of 66.7 kPa (500 mmHg, 19.69 inHg) = point B is indicated on vacuum gauge while the pedal is still depressed.
   Fig 3: Checking Loaded Air Tightness

   Courtesy of SUBARU OF AMERICA, INC.
2. Stop the engine and watch vacuum gauge.

   If the vacuum drop range is less than 3.3 kPa (25 mmHg, 0.98 inHg) within 15 seconds after stopping engine, the brake booster is functioning properly. If defective, refer to "AIR TIGHTNESS CHECK". < Ref. to INSPECTION , Brake Booster. >

3. If any fault is found on brake booster, replace the brake booster with a new one.

Turn off the engine, and set the vacuum gauge reading at "0". Then, check the fluid pressure when brake pedal is depressed. The pressure must be greater than the standard value listed.

Set the vacuum gauge reading at 66.7 kPa (500 mmHg, 19.69 inHg) by running engine. Then, check the fluid pressure when brake pedal is depressed. The pressure must be greater than the standard value listed.