Checking the work
1. Press the brake pedal and start the engine. If the brake pedal sinks slightly, the booster is working properly.
2. With the engine running, press and release the brake pedal several times. Make sure that the pedal stroke does not change (the distance between the pressed ice in the pouring and the floor remains unchanged).
Leak test
3. Start the engine and stop it after 1-2 minutes. Slowly press the brake pedal several times. If the brake pedal moves less distance each time, the booster is airtight.
4. Start the engine, press the brake pedal and hold it down. Stop the engine. If the pedal stroke does not change within 30 seconds, the amplifier is airtight.
Removal
5. The vacuum booster is non-dismountable. Equipment is required to repair it. which is not available at regular service stations. For these reasons, a faulty brake booster must be replaced with a new or reconditioned one.
6. Remove the brake master cylinder (see paragraph 8).
7. Remove the hose connecting the vacuum booster to the engine. Be careful. to avoid damaging the hose mount to the amplifier.
8. Locate the pushrod mounting pin that connects the booster to the brake pedal.
9. Using pliers, remove the cotter pin, then remove the pin.
10. Unscrew the four nuts securing the amplifier to the engine bulkhead (figure 11.10). You will need a portable lamp for this job as the nuts are difficult to access.
11. Remove the amplifier from the bulkhead, then turn it to the right (to the center of the engine) so that the pusher comes out of the bulkhead, then remove the amplifier from the engine compartment.
Installation
12. Installation is carried out in the reverse order of removal. Tighten the amplifier mounting nuts to the specified torque. Also install a new pushrod retaining pin.
13. When replacing the booster, it will be necessary to adjust the clearance between the master cylinder piston and the booster pusher, which is done as follows.
- a) Using a hand vacuum pump, create a vacuum in the booster equal to 500 mmHg. Measure the distance between the end of the tappet and the plane of the master cylinder seating surface. Write down the measured number (figure 11.13,a). We will designate this size with the letter "A".
- b) Measure the distance between the master cylinder flange and the stroke of its piston rod (figure 11.13.6). Write down the measured number. We will designate this size with the letter "B".
- c) Measure the depth of the master cylinder piston recess (figure 11.13,c). Write down the resulting number. We will designate this size with the letter "C".
- d) Subtract the number "C" from "B" and then subtract the resulting number from the dimension "A". The resulting value represents the clearance between the master cylinder piston and the booster pushrod.
- d) Compare the obtained gap value with Technical data. If necessary, adjust the tappet length so that the clearance is within acceptable limits (see below). If "D" is less than the difference between "B-C," the tappet length must be reduced. If "A" is greater than "B-C" increase the length of the pushrod to provide the correct clearance.
14. If the clearance needs adjustment, loosen the lock nut and turn the vacuum booster pusher until. until the required clearance is achieved (Fig. 11.14). After completing the adjustment, tighten the lock nut. Measure the gap again. Repeat the adjustment procedure until the required clearance is obtained.
15. After installing the master cylinder, connect all the lines and bleed the brake system (see paragraph 10).