2. Turn off the engine.
3. Press the brake pedal as hard as you would during normal braking.
4. If the pedal travel is large when pressed for the first time, and decreases with subsequent presses, the brake booster is working properly.
If the seal is broken, check the seal of the following components:
- Check valve (built into the vacuum hose).
- Vacuum tubes and hoses.
- Brake booster.
- Primary and secondary piston seals of the master cylinder.
5. Start the engine again.
6. Press the brake pedal as hard as you would during normal braking.
7. In this state, turn off the engine.
8. Keep the brake pedal depressed for approximately 30 seconds. If the brake pedal height does not change, the system is sealed.
Checking for leaks using a special tool
1. Using a suitable hose, connect a vacuum gauge (special tool) between the brake booster and the check valve.
2. Start the engine and warm it up until the fan runs twice. Press the accelerator pedal until a vacuum of 66.7 kPa (500 mm Hg) is created and stop the engine.
3. Read the vacuum gauge reading.
- Standard vacuum loss in 15 sec: 3.3 kPa (25 mmHg)
4. If the seal is broken, check the seal of the following components.
- Check valve (built into the vacuum hose)
- Vacuum tubes and hoses
- Brake booster
- Primary and secondary piston seals of the master cylinder
Functional check
1. Install the special tools on the master cylinder as shown in the figure.
2. Remove air through the bleed valves of the special tools.
3. Start the engine and warm it up until the fan runs twice.
4. Depress the brake pedal with the force given below and measure the brake fluid pressure at the outlets when the vacuum gauge reads 0 kPa (0 mmHg) (does not increase) and 66.7 kPa (500 mmHg).
Check valve
The check valve is built into the brake booster vacuum hose. If the hose lets air in when blowing from the brake booster side and does not let air in when blowing from the opposite side, then the valve is working properly.