Brake booster
1. Master cylinder; 2. Hose; 3. Gasket; 4. Fork axle; 5. Fork; 6. Cotter pin; 7. Vacuum booster; 8. Gasket; 9. Splitter on the ABS brakes
Checking the operation of the vacuum booster
1. Press the brake pedal several times with the engine off. The pedal travel should not change with each press.
2. Press the pedal and start the engine – on a working booster, the brake pedal should move forward slightly.
Checking for leaks
1. Start the engine, stop it after 1-2 minutes. Slowly press the pedal several times. On a working booster, the pedal stroke should gradually decrease with each press.
2. Start the engine and press the pedal. Keeping the pedal pressed, stop the engine – the pedal position should not change within 30 seconds after stopping.
If the amplifier is faulty, it will need to be replaced; repairing the unit is impossible even in a car service center.
Removal
1. Remove the master cylinder (see subsection 10.9.).
2. Remove the fuel vapor recovery tank (see subsection 7.2.20.).
3. Remove the air filter (see subsection 6.11.).
4. Carefully disconnect the vacuum hose from the booster.
5. Working inside the passenger compartment, remove the steering column cover (see subsection 11.24.).
6. Using a flashlight, locate the vacuum booster pushrod fork where it attaches to the brake pedal. Unpin and remove the fork axle.
7. Remove the four nuts securing the brake booster to the engine compartment bulkhead.
8. Feed the amplifier and remove it when the pins come out of the holes in the bulkhead.
Installation
Installation is carried out in the reverse order of removal.
If a new unit is installed, adjust the clearance between the brake master cylinder pushrod and the booster pushrod. To do this, do the following.
1. There should be no gap between the vacuum booster and master cylinder pushers. If the gap is not zero, the brake pedal travel increases. If, on the contrary, the booster pusher rests against the cylinder pusher, the wheels may not be released.
2. Measure the extension of the pushrod above the gasket on the booster housing. This is dimension A.
3. Measure the distance from the end of the master cylinder to the flange plane. This is dimension B.
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4. Measure the distance from the end of the master cylinder to the bottom of the piston recess. This is dimension C.
6. The gap between the pusher and the piston is (B – C) – A and should be 0. If necessary, adjust the protrusion of the vacuum booster pusher.
7. To adjust the tappet, squeeze the tappet by the knurled neck and rotate the tappet tip to set the protrusion A so that the gap is equal to B – C. Check the gap again. Repeat the adjustment if necessary.
8. When finished, install the master cylinder, connect the tubes, adjust the pedal height and free play. Remove air from the hydraulic drive.