Leak test
1. Connect a vacuum gauge between the brake booster and the check valve.
2. Start the engine, adjust the engine speed with the accelerator pedal so that the vacuum gauge reading is 40.0-66.7 kPa (300-500 mmHg), then turn off the engine.
3. Take readings from the vacuum gauge.
4. If the vacuum gauge reading drops by 2.7 kPa (20 mmHg) or more after 30 seconds, check for leaks at the following components:
- Check valve
- Vacuum hose, tube
- Seals
- Brake booster
- Master cylinder
Note: Do not attempt to disassemble the brake booster. Replace the brake booster assembly with a new one.
Checking functionality
1. Connect the vacuum gauge in the same way as when checking for leaks.
2. Using adapters (special tool), connect the oil pressure gauges to the master cylinder.
3. Release air through the fittings.
4. Start the engine and let it run at idle speed.
5. Ask an assistant to press the brake pedal with a force of 98 N (10 kgf/m).
6. At each vacuum value, the following pressure values should be observed on the pressure gauges.
| Vacuum, kPa (mmHg) | N (kgf/m) | kPa (kgf/cm²) |
| 0(0) | 98 (10) | 0 (0) |
| 294 (30) | 1400 (14) | |
| 66,7 (500) | 98(10) | 3600 (37) |
| 294 (30) | 9000 (292) |
7. If the reading is outside the range specified above, check the master cylinder for leaks.
Checking the check valve
1. Disconnect the vacuum hose from the brake booster.
2. Start the engine and let it idle. There should be a vacuum. If there is no vacuum, the check valve is not working properly. Replace the check valve and retest.
