The area around the brake booster with a 1.6 liter engine: 1 - a reservoir with brake fluid; 2 - brake booster; 3 - a vacuum tube from the intake manifold; 4 - ejector to increase the reduced pressure
The same view as in the photo above, but with a six-cylinder engine: 1 - brake fluid reservoir; 2 - brake booster; 3 - a vacuum tube from the intake manifold; 4 - return valve in the vacuum tube
Order of execution
1. Engine must be off.
2. Depress the brake pedal 10 times.
3. Keep the pedal depressed and start the engine.
4. If the brake booster is working properly, then the pedal should move a little. If the pedal does not go down, then the brake booster is faulty.
5. If the brake booster fails, the defect most likely lies in the low pressure system: the vacuum hose from the intake manifold to the brake booster is leaky, the return valve in the vacuum hose is leaky, a defect in the rubber ring between the brake master cylinder and the servo drive or membrane brake booster.
6. To check the return valve, remove the vacuum hose from the servo.
7. It is blown, suction is unacceptable.
8. The check valve is only sold with a vacuum hose.
9. To replace the damaged rubber ring between the main brake cylinder and the booster, you need to dismantle the cylinder.
10. In conclusion, there is still a defect in the brake cylinder itself. In this case, repair is not possible - it must be replaced.
Removing the brake booster
To loosen the brake pressure rod on the brake pedals, Audi uses a special tool 3289. Unfortunately, this tool cannot be dispensed with. Sequencing:
1. Remove the master brake cylinder.
2. Remove the vacuum hose.
3. Unscrew the two fixing bolts of the brake booster (TORX T45).
4. Dismantle the pocket on the left under the dashboard (chapter Salon).
5. Disconnect the brake light and speed control ventilation valve switch on the brake pedal.
6. Install special tool 3289 on the brake pedal lever. Now you can disconnect the brake booster push rod from the pedal (pull the pedal back).
7. Remove the brake booster from the engine compartment.
8. If a new brake booster is installed, then the length of its control rod must be adjusted in the dismantled state.
9. Distance between the end of the control rod (it must be vertical) and adjacent surface with two threaded holes should be 158.5 mm (tolerance 0.5 mm).
10. After adjustment, tighten the locknut.
11. Lightly grease the pivot pin before mounting.
12. Use a new pivot pin retainer and new self-locking nuts. Install a new O-ring between the brake booster and the master cylinder.
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