Vacuum Brake Booster: Testing and Inspection

Check Brake Booster







Inspect
1 Operate brake pedal several times until vacuum in brake booster is reduced
2 Disconnect tester from brake booster
3 Connect, disconnect pressure tester (051) to connection at brake caliper

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

4 Fit, remove pedal force measuring instrument (060) at brake pedal
5 Start the engine and create a vacuum of 0.75 - 0.80 bar by pressing and then suddenly releasing the accelerator pedal.

NOTE: If a considerably lower vacuum is achieved or if the vacuum decreases immediately, the O-ring between the brake booster and tandem master brake cylinder may be damaged, or the check valve in the vacuum line may be defective, Check non-return valve

- Vehicle with diesel engine - check vacuum pump:
- Model 202 with Engine 601
- Model 202 with Series 604, 605 engine
- Model 140 with Engine 603

6 Supply brake pedal with specified force and read line pressure (see line pressure under Adjustments)
- 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.
7 Bleed brake system.