Vacuum Brake Booster: Service and Repair
Removing and installing brake boosterTools
Preliminary work
1. Switch off the ignition.
2. Remove both wiper arms.
3. Remove cover in engine compartment.
4. Remove cowl panel.
Removing brake booster
Note:
^ During assembly work on hydraulic connections, the electrical plug connections on the hydraulic unit must always be connected. This prevents the plug connections on the hydraulic unit and the inside of the connectors being splashed with brake fluid or water.
^ Damp connectors must be wiped dry before disconnection.
^ Brake fluid on electrical contacts (even thinned brake fluid) leads to corrosion and may cause faults in the system.
The brake master cylinder is located on the left in the engine compartment, under the cowl panel cover -arrow-, together with the brake booster.
Note:
^ Brake lines are to be sealed with suitable plugs.
^ To catch escaping brake fluid, place a cloth under the brake booster.
1. Push both connectors -arrows- on the plenum panel (oxygen sensor cable) from the bracket.
2. Open the cable clip on the plenum panel and loosen the cable.
3. Remove left plenum panel partition.
4. Partly remove the brake master cylinder (brake fluid reservoir).
5. Disconnect the vacuum line on the brake booster.
6. Disconnect the connector from distance sensor of the brake booster -arrow-.
7. Unclip the cable over the brake booster from the holders -arrows- and pull upwards.
8. Unclip the brake line to left front wheel out of the bracket underneath the relay carrier.
9. Remove the brake master cylinder.
10. Loosen two M6 screws on the lower closing panel -arrows- (upper screw head covered) (shown here when fitting the brake booster, relay carrier removed).
Note:
^ If the rubber bushes stick to the holders in the plenum panel when removing the relay carrier, these must be fitted in the openings provided before being inserted again.
11. Release the relay carrier in the plenum panel and hinge it to one side. To do this, unclip the six plugs in the rear section of the relay carrier (-arrow- and right marking).
12. Remove the cover under the dashboard on the driver's side in the passenger compartment.
13. Pull off connector of stop light switch -arrow- and remove the complete holder.
Note:
^ When loosening the pushrod of the brake booster with the unlocking tool T10189 from the pushrod of the pedal, the tool must first be inserted and then the brake pedal pulled out into the passenger compartment.
14. Release brake pedal from pushrod -arrow- of brake booster with unlocking tool.
15. To do this, insert the unlocking tool T10189 from below into the bush on the brake pedal -arrow-.
16. Remove the four M8 lock nuts on the brake booster in the passenger compartment.
17. Remove front left wheel housing liner.
18. Disconnect the brake line in the wheel housing on the intermediate piece -arrow- and seal with suitable plugs.
19. Remove both clips for the air-conditioning lines in the plenum panel.
20. Pull the brake lines to the brake master cylinder and left front wheel carefully forward and press the air-conditioning lines down. Make sure that the boot on the brake booster -arrow- does not get stuck in the duct to the passenger compartment.
21. Carefully pull out the brake booster -direction arrow- to the front.
Installing brake booster
DANGER:
Porsche Stability Management does not work without values for the current brake pressure.
^ Danger of personal injury and material damage when the hydraulic unit is not calibrated.
^ After assembly of the brake master cylinder or hydraulic unit, the pressure sensor must be calibrated with the Porsche System Tester.
^ To do this, calibrate the pressure sensor in the menu >> PSM >> Calibration >> Pressure sensor <<.
^ The security code is stored under menu >> PSM >> Actual values >> Security code <<. The code is entered in the last four positions.
Note:
^ Absolute cleanliness is necessary when installing the brake booster as well as the adjacent brake master cylinder. Dirt can cause faults in the system.
^ Calibrate the vehicle with the Porsche System Tester.
^ Bleed the vehicle according to the plan to ensure full operation of the brake system.
^ When inserting the brake booster, make sure the brake pushrod and boot are guided correctly.
^ Pay attention to tightening torques.
1. Carefully pull the brake lines of the brake master cylinder and left front wheel forward and press the air-conditioning lines downward.
2. Carefully insert the brake booster -direction arrow-.
3. Guide the- pushrod of the brake booster through the opening in the passenger compartment. Ensure the boot is seated correctly.
4. Fit the brake booster with four M8 fastening nuts.
5. Press the brake pedal forward until the ball socket engages in the mounting point.
6. Fit the holder for the stop light switch and connect the connector -arrow-.
7. Fit the cover on the driver's side.
8. Fit the clamps of the air-conditioning lines.
Note:
^ If the rubber bushes stick to the holders in the plenum panel when removing the relay carrier, these must be fitted in the openings provided before being inserted again.
9. Install relay carrier in the plenum panel. To do this, fit the six connectors in the rear section of the relay carrier (-arrow- and right marking).
10. Join the closing panel using the two M6 screws -arrows- (shown here when fitting the brake booster - relay carrier removed).
11. Join the brake line in the front left wheel housing (remove sealing plugs).
12. Install front left wheel housing liner.
13. Clip the brake line to left front wheel in the bracket underneath the relay carrier in the plenum panel.
14. Connect the plug on the distance sensor of the brake booster.
15. Connect vacuum pipe to the brake booster.
16. Fit brake master cylinder.
17. Fit left plenum panel partition.
Subsequent work
1. Fit the right and the rear covers.
2. Install both wiper arms.
3. Bleed the vehicle.
4. Calibrate the pressure sensor with the Porsche System Tester.