8.2. vacuum booster: A - vacuum chamber; B - atmospheric chamber; С, D – channels; 1 - stock; 2 – a sealing ring of a flange of the main cylinder; 3 – a cup of the case of the amplifier; 4 - adjusting bolt; 5 - rod seal; 6 - diaphragm return spring; 7 – hairpin of the amplifier; 8 - sealing case; 9 - amplifier housing; 10 - diaphragm; 11 - amplifier housing cover; 12 - piston; 13 - protective cover of the valve body; 14 - air filter; 15 - pusher; 16 - pusher return spring; 17 - valve spring; 18 - valve; 19 - bushing of the valve body; 20 - stock buffer; 21 - valve body
Rubber diaphragm 10 (pic. 8.2) Together with valve body 21, the cavity of the vacuum booster is divided into two chambers: vacuum A and atmospheric B. Chamber A is connected by a hose to a receiver on the engine inlet pipe. The valve body 21 is plastic. At the exit from the cover, it is sealed with a corrugated protective cover 13. In the valve body, there is a rod 1 of the main cylinder drive with a support sleeve, a stem buffer 20, a piston 12 of the valve body, a valve 18 assembly, return springs 16 and 17, respectively, of the pusher and valve, an air filter 14 and pusher 15.
When the pedal is pressed, the pusher 15, the piston 12, and after them the valve 18 moves until it stops against the seat of the valve body. At this time, chambers A and B are separated. With further movement of the piston, its seat moves away from the valve and through the resulting gap, chamber B is connected to the atmosphere. The air that enters through the filter 14 into the gap between the piston and the valve and channel D creates pressure on the diaphragm 10. Due to the pressure difference in chambers A and B, the valve body moves along with the stem 1, which acts on the piston of the brake master cylinder.
When the pedal is released, the valve moves away from its body and chambers A and B communicate with each other through the resulting gap and channel C.
If the vacuum booster fails, the force on the brake pedal increases significantly, which negatively affects driving.
To repair the vacuum booster, a special tool is required, so it is recommended to replace it as an assembly.
To check the operation of the vacuum booster with the engine off, press the brake pedal 5-6 times. Keeping the brake pedal depressed, start the engine. The brake pedal should move forward. If this does not happen, first check the tightness of the vacuum hose connections and check valve operation.