Leak test
1. Connect a vacuum gauge between the brake booster and stop valve.
2. Start the engine, adjust the engine speed with the accelerator pedal so that the vacuum gauge readings are 40.0-66.7 kPa (300-500 mmHg), then stop the engine.
3. Take readings from the vacuum gauge.
4. If after 30 seconds the vacuum gauge readings fall by 2.7 kPa (20 mmHg) or more, check for leaks on 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.
Health check
1. Connect the vacuum gauge in the same way as for the leak test.
2. Using adapters (special tool) connect oil gauges to the master cylinder.
3. Release the 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, the pressure gauges should show the following pressures.
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 readings are outside the limits above, check the master cylinder for leakage.
Stop valve check
1. Disconnect the vacuum hose from the brake booster.
2. Start the engine and let it run at idle speed. There must be a vacuum. If there is no vacuum, the stop valve is not working properly. Replace check valve and recheck.