Converting Brake Booster (Bellows)
Converting brake booster (bellows)
^ 2 bellows variants have been installed as standard in the Boxster, (first version -A- and new/current version -B-).
^ The bellows variant of the first version -A- is no longer available as a spare part. The version must be installed in the event of repair -A1- (conversion described in the following).
Note! The conversion described in the following only applies for vehicles in which the bellows first version A (with 2 rubber bellows -1 and 2-) is installed!
Overview of bellows conversion
^ To convert the bellows variant -A- to version -A1- the hydraulic unit, the brake booster -4- with brake master cylinder and the intermediate piece -11- must be removed.
^ The assembly of the brake master cylinder with the brake booster -4- must not be disconnected for removal and installation if both parts should be continued to be used!
^ To remove the intermediate piece -11-, the battery must be removed! This will prevent damage of the components in the surrounding area.
^ The following parts must be exchanged or replaced for first installation of variant -A1- (replacement aus fuhrung):
- Remove short bellows -2- on the brake booster and the long bellows -1- on the firewall.
- Remove the grommet (rubber groove ring) -3- for mounting the long (former) bellows (not replaced).
- The following parts are used in place of the removed parts -1 / 2 / 3-: Bellows -B- (already mounted on new brake boosters), connection sleeve -7.1- with sealing ring -7.3-, the seal for the firewall -7.2- and the hose clamps (clamps) -6 and 6.1-.
- The two push rods -12 and 9- are to be replaced with the modified version -12.1 and 9.1-.
- Additional assembly - Boxster model '97: The brake pedal must be replaced in addition to the new push rod -9.1- in Boxster model year '97: Go to "Additional assembly - Boxster model '97"
Difference in the push rods:
^ Push rods -12.1- with thread and fastening nut -13.1- in place of push rod -12- with retainer -13-.
^ A guide for the bellows -arrow- is present in the previous push rod -9-. A guide is not present and not permissible in the new push rod -9.1-!
Removal
1. Switch off ignition. Remove cover -A + B- and battery cover.
2. Remove spare wheel.
3. Remove brake booster -C- - Go to "Removing and installing brake booster".
Note!
^ The brake master cylinder -B- and the hydraulic unit -D- must be removed to remove and install the brake booster -C-.
^ The assembly of the brake master cylinder -B- with the brake booster -C- must not be disconnected for removal and installation if both parts should be continued to be used!
4. Remove battery -1- (necessary to remove intermediate piece -11-)! Remove alarm horn on the intermediate piece -11-.
5. Undo intermediate piece -11- -arrow- (2 M8 nuts and hexagon socket head bolt) and remove in the direction of the battery. Unclip air conditioning line -2- from the holder.
6. Remove the bellows -1- on the fire wall and the bellows -2- on the brake booster. Pull off the grommet (rubber groove ring) -3-.
Note! The grommet -3- is not replaced!
7. Undo brake pushrod -9- on the brake pedal and remove.
Note! The former brake pushrod -9- with guide (double rib) -arrow- is to be replaced with the brake pushrod -9.1- without guide!
Additional assembly - Boxster model '97
^ Brake pedal -14- must be replaced by -14.1- in addition to the new push rod -9.1- in Boxster model year '97. The figure shows 1 brake pedal with old -14- and new -14.1- push rod connection.
Note!
^ Installation of the new brake pedal -14.1- is necessary as the connection to the push rod in model '97 -9- is made with a pin (self-aligning bolt) -16- with a mechanical locking device -15-. Connection as of '98 model: Threaded bolt -16.1- with threaded bushing -15.1-.
^ The new brake pedal -14.1- is fitted with a bearing (pressed in) (at the connection to the push rod) while the brake pedal of model '97 -14- (in this area) is fitted with a bushing.
^ The clip -X- on the push rod of model '97 -9- is not included!
- Remove the brake pedal and install new brake pedal - Go to Remove and install brake pedal. Allocation/part numbers are to be referred to in the Technical Information notice.
Fitting
Caution! Material damage to the connection to the brake pedal if the tightening torque used on the connecting pin is too great!
^ It is essential to observe the specified tightening torque on the connection thread bushing/pin!
1. Install new brake pushrod -9.1-. Tighten the threaded bushing -arrow- of the pin to 10 Nm (7.5 ft. lbs.). (Please observe)!
2. Insert seal -7.2- (without lubricant) into the firewall. It is essential to ensure correct seating! Then insert (push in) the connection sleeve -7.1- into the seal -7.2- using rubber sliding compound for example Capella or tire mounting paste. Recheck that it is seated correctly and correct if necessary!
3. Mount seal -7.3- and coat with Capella or tire mounting paste.
4. Mount intermediate piece -11- (2 M8 nuts and hexagon socket head bolt). Tightening torque of the 2 M8 nuts = 23 Nm (17 ft. lbs.).
5. Install battery.
6. Install new pushrod (if not already present) -12.1- in place of -12-. When doing so, observe installation dimension X (138 mm).
Basic setting of the push rod -dimension X- is 138 mm (set in new brake boosters)! If necessary, correct during the relevant work!
7. Install brake booster and brake master cylinder with mounted bellows -B- and tightened clamps -6-.
Note! Before using the brake booster, push the screw clamp -6.1- onto the bellows -B- or onto the brake pushrod!
8. Tighten fastening screws of brake booster (Torx T 45) -arrow- to 23 Nm (17 ft. lbs.). Fit the vacuum line for the brake booster.
- If the brake master cylinder has been removed, tighten the fastening nuts (M14) to 49 Nm (36 ft. lbs.).
9. Connect the 2 push rods. To do so, mount the fastening nuts -arrow-
Note!
^ Adjusting the brake pushrod length changes the position of the brake pedal.
^ Perform a fine adjustment of the brake pushrod if the correct position of the brake pedal is not given!
^ After the brake pushrod is adjusted, check the brake light switch adjustment!
10. Check the position of the brake pedal -Dimension X = 45 + 5 mm-. Perform measurement between the center of the brake pedal plate and the accelerator. Perform a fine adjustment of the brake pushrod if the correct position of the brake pedal is not given.
- Precise adjustment of brake pushrods: Undo the lock nut for this purpose and the turn the push rod accordingly at the hexagon -arrow- until -dimension X = 45 + 5 mm- has been achieved. Subsequently re-tighten the the lock nut.
11. Check the setting of the brake light switch -1-. The pedal must move a perceptible distance of approximately 5 to 10 mm before the brake light lights up. At the same time, check (make sure) that the brake light lights up before the pedal meets perceptible resistance or before brake pressure builds up. If necessary, set/re-adjust.
12. Fit the bellows -B- to the connection sleeve -7.1- and secure with the screw clamp -arrow-.
13. If necessary, fit the alarm horn to the intermediate piece and clip in the air-conditioning line.
14. Install hydraulic unit.
15. Bleed brakes (vehicle with and without TC).
Note!
^ First bleed brakes as usual!
^ Only after the conventional bleeding should the return pump actuation be performed (continue bleeding) with the Porsche System Tester 2 (PST 2) in vehicles with Traction Control (TC)! If this is not observed, damage can occur to the return pump/booster pump!
^ To bleed at rear on right with running return pump motor (TC), the bleeding device should remain connected and switched on! Bleeding pressure approximately 2.0 bar.
16. Bleed the clutch in manual transmission vehicles.
17. When replacing the hydraulic unit in vehicles with ABS/TC (4-channel system), code the control module (manual transmission or Tiptronic).
18. Carry out the following tests:
- Check the system (brake lines and connections) for leaks.
- Read out and erase the fault memory of the ABS control module with the Porsche System Tester 2 (PST 2). Additionally, perform the static test in the system.
- Check electrical and hydraulic lines (brake lines) for incorrect assignment using the PST 2.
Note! The exchange test checks that the brake lines/solenoid valves are assigned to the correct brake calipers (wheels)!
- Then start the engine. The ABS or ABS/TC related lights in the instrument cluster must go out when the engine is running.
- Carry out a function check of the brakes. Then perform a short test drive and perform at least one ABS control operation, taking the road conditions into consideration. Read out the ABS fault memory again. There must not be any stored faults.
19. Perform the work which is necessary due to disconnecting the battery; See Work Instruction After Disconnecting the Battery.
20. Fit Cover -A/B- and Spare wheel.