Leak test
1. Connect a vacuum gauge A between the vacuum booster and the non-return valve.
2. Start the engine, press the accelerator pedal to set the speed at which the discharge after the throttle valve is 66.7 kPa, then turn off the engine.
3. Read the vacuum gauge.
If the vacuum decreases by 2.7 kPa or more within 30 seconds, then it is necessary to check the tightness of the following system elements:
- control valve;
- vacuum hoses, pipelines;
- seals;
- brake booster;
- master brake cylinder.
Note. The brake booster cannot be dismantled and repaired. In the event of a malfunction of the tomoz amplifier, it must be replaced.
Checking the operation of the brake booster
1. Connect the vacuum gauge in the same way as for the leak test.
2. Connect fluid gauges A to the brake master cylinder with tee fittings as shown.
3. Bleed air through bleed valves B.
4. Start the engine and let it idle.
5. Ask the assistant to press a brake pedal. The assistant must press the pedal with a force of 98 N and 294 N on the pressure gauge scale A.
6. The readings of the measuring pressure gauges for various values of vacuum in the intake tract should be as follows.
VSA
7. If the pressure of the brake fluid after the main brake cylinder is less than the values given in the table, then you should check the tightness of the sealing cuffs of the main brake cylinder.
Checking the brake booster check valve
1. Disconnect the brake booster hose (check valve built into it) And from the brake booster.
2. Start the engine and let it idle. From the side of the open end of the vacuum hose, air leakage should be felt. If there is no air leakage, then the check valve is faulty. Replace vacuum line with non-return valve and retest.