Vacuum Brake Booster: Testing and Inspection

Check Brake Booster

Model 203:

Inspect
1 Operate brake pedal several times until vacuum in brake booster (16) is reduced
2 Connect tester (030) at brake booster

NOTE: Test connection (031) for testing the check valve (17) or brake booster (16).

3 Connect pressure tester (051) with connection fitting to brake caliper
4 Connect pedal force measuring instrument (060) at brake pedal
5 Start engine and create a vacuum of 0.75 to 0.80 bar by accelerating and then suddenly releasing the accelerator pedal

NOTE:
- If only a slightly smaller vacuum is achieved or if the vacuum drops immediately, the the gasket between the brake booster and the master brake cylinder may be damaged or the check valve in the vacuum line may be defective, checking non-return valve
- Removing and installing master brake cylinder, replacing gasket

6 Apply specified force to brake pedal and read off line pressure.
- To cover measurement errors as far as possible (wrong force on brake pedal, wrong vacuum) and measurement scatter of the gauges, a tolerance of ± 10 bar on the specified value is permissible.

NOTE: The measured value must be within the value range.

7 Disconnect tester (030) at brake booster
8 Disconnect pressure tester (051) with connection fitting from brake caliper
9 Remove pedal force measuring instrument (060) at brake pedal
10 Bleed brake system.

NOTE: After checking, only bleed the brake caliper to which the pressure tester was connected.