 printable version
Check the brake servo
Checking without measuring device Stage 1
| PERFORMANCE ORDER | | 1. With the engine off, repeatedly press the brake pedal. | | 2. Hold the pedal down, start up the engine. |  | 3. If the brake pedal is moved down immediately after the engine starts, it indicates normal operation of the vacuum brake booster. |
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Stage 2
| PERFORMANCE ORDER | | 1. Start up the engine. | | 2. After 1-2 minutes, stop the engine. | | 3. Press the brake pedal with ordinary effort. | | 4. If the first pedal stroke - long and the second course is shorter than the first move, it indicates normal operation of the vacuum brake booster. |  | 5. Otherwise, check up the unilateral vacuum valve or a vacuum hose for damage and check the reliability of their fastenings. |
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Phase 3
| PERFORMANCE ORDER | | 1. Start up the engine. | | 2. Press the brake pedal with ordinary effort. | | 3. Stop the engine. | | 4. Slowly depress the brake pedal and hold it for 30 seconds. |  | 5. If the pedal height does not change, the vacuum brake booster is working properly. | 6. Otherwise, check up the unilateral vacuum valve or a vacuum hose for damage and check the reliability of their fastenings.
If the problem still persists, perform a detailed inspection using a pressure gauge and a vacuum gauge. |
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Check with a meter Plug gauge, a vacuum gauge and gauge pressure force on the pedal, as shown in Fig. After removing the air from the pressure gauge perform the test in accordance with the three items shown below.
A warning  Use commercially available sensors and measuring the pressure force on the pedal.
a) Check the vacuum reduction Unloaded condition | PERFORMANCE ORDER | | 1. Start up the engine. | | 2. Turn off the engine when the vacuum gauge readings will be equal to 500 mm Hg |  | 3. Keep an eye on the meter readings of the vacuum for 15 seconds. If they are in the range 475-500 mm Hg, then the system is working. |
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Loaded condition
| PERFORMANCE ORDER | | 1. Start up the engine. | | 2. Press the brake pedal with a force of 196 N. | | 3. While holding the pedal down, turn off the engine when the meter will amount to 500 mm Hg vacuum |  | 4. Keep an eye on the meter readings of the vacuum for 15 seconds. If the vacuum gauge readings are within 475-500 mmHg, system is OK. |
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b) Verification of hydraulic pressure
| PERFORMANCE ORDER |  | 1. If the engine is off (0 mm Hg vacuum) pressure of the fluid corresponds to the following requirements, the system is working.
| Power pedal | Fluid Pressure | | 196 N | 1,177 kPa |
|  | 2. Start up the engine. Press the brake pedal when the meter will amount to 500 mm Hg vacuum If the fluid pressure corresponds to the following requirements, the system is working.
| Power pedal | Fluid Pressure | | 196 N | 1,177 kPa |
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