Peugeot 405 Manual

Vacuum servo unit - testing, removal and refitting
Braking system / Vacuum servo unit - testing, removal and refitting


Testing
1 To test the operation of the servo unit, depress the footbrake several times to exhaust the vacuum, then start the engine whilst keeping the pedal firmly depressed. As the engine starts, there should be a noticeable УgiveФ in the brake pedal as the vacuum builds up. Allow the engine to run for at least two minutes, then switch it off. If the brake pedal is now depressed it should feel normal, but further applications should result in the pedal feeling firmer, with the pedal stroke decreasing with each application.

2 If the servo does not operate as described, first inspect the servo unit check valve as described in Section 16.

3 If the servo unit still fails to operate satisfactorily, the fault lies within the unit itself.

Repairs to the unit are not possible - if faulty, the servo unit must be renewed.

Removal
4 Disconnect the battery negative lead.

5 Remove the windscreen wiper motor/ linkage assembly as described in Chapter 12.

6 Disconnect the wiring from the low brake fluid level warning sensor.

7 Pull the vacuum check valve from the grommet in the top of the servo (see illustration).

15.7 Pulling the vacuum check valve from the servo
15.7 Pulling the vacuum check valve from the servo

8 Unscrew the two nuts securing the master cylinder to the brake vacuum servo unit, then ease the master cylinder up to disengage it from the servo, without disconnecting the fluid pipes. Take care not to strain the fluid pipes. If necessary, release the fluid pipes from their locating clips to enable them to move sufficiently.

9 Working in the driverТs footwell, remove the carpet trim panel from under the facia to expose the pedal assemblies.

10 Where applicable, working under the facia, unscrew the bolts securing the relay bracket and the wiring connector bracket(s) to improve access.

11 Where applicable, depress the retaining clip and detach the end of the clutch cable from the pedal (see Chapter 5).

12 Disconnect the wiring plug from the stop light switch.

13 Prise off the brake and clutch pedal rubbers.

14 Working in the scuttle, unscrew and remove the four nuts securing the servo to the scuttle (see illustration).

15.14 Unscrew the nuts (arrowed) securing the servo to the scuttle
15.14 Unscrew the nuts (arrowed) securing the servo to the scuttle

15 Manoeuvre the complete vacuum servo, pedal bracket and pedal assembly from the scuttle (see illustration).

15.15 Removing the vacuum servo/pedal bracket assembly
15.15 Removing the vacuum servo/pedal bracket assembly

16 Unscrew the four nuts securing the servo to the pedal bracket, and withdraw the servo (see illustration). Where applicable recover the gasket.

15.16 Unscrew the nuts (arrowed) securing the servo to the pedal bracket
15.16 Unscrew the nuts (arrowed) securing the servo to the pedal bracket

17 The servo is a sealed unit, and if faulty, the complete unit must be renewed.

Refitting
18 Refitting is a reversal of removal, bearing in mind the following points.

a) Use a new gasket when refitting the servo.

b) Refit the wiper motor/linkage assembly with reference to Chapter 12.

c) Check the stop light adjustment with reference to Section 22.

d) Check the clutch cable adjustment as described in Chapter 6.


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