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Brake Booster Inspection

Special Tools Required

Pressure gauges set, 16,000 kPa

Combination gauge kit


Tube joint adapter

Pressure gauge joint pipes, 10 x 1.0 mm

Pressure gauge joint pipes, 12 x 1.0 mm
Leak Test
  1. Install the vacuum gauge (A) between the brake booster and check valve.
  1. Start the engine, adjust the engine speed with the accelerator pedal so that the vacuum gauge readings show 66.7 kPa (500 mmHg, 19.7 in.Hg), then stop the engine.
  1. Read the vacuum gauge.
    If the vacuum reading decreases 2.7 kPa (20 mmHg, 0.8 in.Hg) or more after 30 seconds, check following parts for leaks.
    • Check valve
    • Vacuum hose, pipe
    • Seals
    • Brake booster
    • Master cylinder
    NOTE: Do not try to disassemble the brake booster. Replace the brake booster as an assembly with a new one.

Function Test
  1. Install the vacuum gauge as same as the leak test.
  1. Connect the oil pressure gauges (A) to the master cylinder using the attachments pressure gauge joint pipes as shown.
  1. Bleed air through the valves (B).
  1. Start the engine, and let it idle.

  1. Have an assistant depress the brake pedal with a 98 N (10 kgf, 22 lbf) and 196 N (20 kgf, 44 lbf) of pressure measuring with a commercially available pressure gauge (A).
  1. The following pressures should be observed at the pressure gauges in each vacuum.
    Vacuum booster Vacuum kPa (mmHg, in.Hg)
    Brake pedal pressure N (kgf, lbf)
    Master cylinder oil pressure kPa (kgf/cm 2 , psi)
    0 (0, 0)
    98 (10, 22)
    0 (0, 0)
    196 (20, 11)
    Except LHD model of M/T
    577 (5.9, 83.7)
    LHD model of M/T
    501 (5.1, 72.6)
    66.7 (500, 19.7)
    98 (10, 22)
    KE, KG models of i-SHIFT
    5,393 (55, 782)
    KG model of 5MT
    5,153 (52.5, 747)
    Except LHD model of M/T
    4,523 (46.1, 656)
    LHD model of M/T
    4,235 (43.2, 614)
    196 (20, 11)
    KE, KG models of i-SHIFT
    8,125 (82.9, 1,178)
    KG model of 5MT
    8,060 (82.2, 1,169)
    Except LHD model of M/T
    9,538 (97.3, 1,383)
    LHD model of M/T
    9,468 (96.5, 1,373)

  1. Inspect the master cylinder for leaks if the readings do not fall within the limits shown above.

Booster Check Valve Test
  1. Disconnect the brake booster vacuum hose (A) at the booster.
    NOTE: If the check valve (B) is faulty, replace the brake booster vacuum hose/check valve as an assembly.
  1. Start the engine, and let it idle. There should be vacuum available. If no vacuum is available, the check valve is not working properly. Replace the brake booster vacuum hose and check valve, and retest.

Brake Assist Check (For KE, KG ABS models)
Make sure the brake assist is not activated early in case of installing brake booster and brake pedal. You may hear mechanical noises when pressing the brake pedal with some vacuum remained in brake booster. That could be caused in a normal condition, it would be not a symptom of abnormalities. The noises would not be created in the condition that the brake booster has no vacuum.
  1. Press the brake pedal hard.
  1. Release the brake pedal and start the engine, and allow the engine warm up to normal operating temperature.
  1. Test-drive the vehicle at low speed.
  1. Press the brake pedal lightly, and make sure it does not cause a rapid brake.

Brake Booster Pushrod Thickness (Reference)
NOTE: The illustration shows except KE, KG ABS models.
KE, KG ABS models:
123−124 mm (4.84−4.88 in.)
Except KE, KG ABS models:
115.5−1116.5 mm (4.55−4.59 in.)