Vacuum booster
The vacuum amplifier uses a double diaphragm and a vacuum principle of operation. In normal mode, when the brake pedal is not depressed, negative pressure acts on both sides of the diaphragm. When the pedal is pressed, one of the amplifier chambers is connected to the atmosphere and the resulting pressure creates an additional force acting on the master cylinder piston. When the brake pedal is released, this chamber is disconnected from the atmosphere. The air is then sucked out of the booster through a vacuum check valve under vacuum.
Important: If any hydraulic element was removed or disconnected during the repair, it may be necessary to bleed the brake system completely or partially. See Part 4A. Hydraulic brakes.
Checking the operation of the vacuum booster
1. With the engine off, equalize the pressure in the vacuum chamber of the amplifier with atmospheric pressure. To do this, depress the brake pedal several times.
2. Depress the pedal and hold it in this position. Start the engine.
3. If the pedal continues "fall through", which means that it is affected by an additional force, which indicates the health of the amplifier.
If the brake pedal does not drop, the vacuum system may be (vacuum hoses, valves, etc.) faulty and needs to be checked.
If the check of the vacuum system did not reveal a malfunction, then the amplifier itself is faulty.
Tightening torques for threaded connections
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Application
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N·m
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lb-ft
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lb-in
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Nuts of fastening of the amplifier to the dashboard
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22
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16
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-
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