Hydraulic Control Assembly - Antilock Brakes: Service and Repair
Removing and installing hydraulic unitTools
Preliminary work
1. Remove plenum panel cover.
2. Using the bonnet stay 97040 the bonnet can be opened wider for better accessibility of the plenum panel. To do this, remove the front gas spring and mount the bonnet stay.
3. Remove the DME control module -arrows-.
Removing hydraulic unit
Note:
^ When fitting the hydraulic connections, the electric plug connections on the control units must remain connected as long as possible. This prevents the plug connections on the hydraulic unit or in the connectors inside from being splashed with brake fluid or water.
^ Any damp connector must be wiped dry before being disconnected from the connector on the hydraulic unit. If necessary, provide the connector with a suitable protector.
^ Brake fluid on electrical contacts (even thinned brake fluid) leads to corrosion and may cause faults in the system.
^ The brake lines must not be bent in the area of the hydraulic unit.
^ Clean the interfacing points of the brake lines, but not with cleaning agents.
^ Rinse off any brake fluid emerging thoroughly with water.
The -> see figure hydraulic unit is installed in the plenum panel on the front right, under the DME control unit.
Note:
^ When fitting the hydraulic connections, the electric plug connections on the control units must remain connected as long as possible. This prevents the plug connections on the hydraulic unit or in the connectors inside from being splashed with brake fluid or water.
^ Any damp connector must be wiped dry before being disconnected from the connector on the hydraulic unit. If necessary, provide the connector with a suitable protector.
^ Brake fluid on electrical contacts (even thinned brake fluid) leads to corrosion and may cause faults in the system.
^ The brake lines must not be bent in the area of the hydraulic unit.
^ Clean the interfacing points of the brake lines, but not with cleaning agents.
^ Rinse off any brake fluid emerging thoroughly with water.
1. Release the ground cable -arrow-, unclip the wiring harness and set it aside.
2. Remove the support for the DME control unit -arrow-.
3. Remove the housing of the intake air duct. To do so, loosen the two external fastening nuts and the two retaining clips in the inside of the air duct.
4. Provide a suitable protector for the control unit connector.
5. Activate the brake pedal by hand using the brake pedal loader, (do not clamp it yet!). Plug the vent hose of the vent bottle onto the front left and rear left bleeder screw of the brake caliper (2nd fitter required). Open the bleeder screws until the brake pedal is completely pressed down. Tighten the brake pedal loader and close the bleeder screws. This will close the central valves of the tandem brake master cylinder so that only a little brake fluid can flow out of the opened brake system.
6. A sufficient number of cloths should be put under the hydraulic unit to absorb any brake fluid emerging. If some runs into the plenum panel none the less, immediately rinse thoroughly with water.
7. Mark the -> see figure lines on the hydraulic unit (color marking, etc.) and remove. Seal the loosened lines with suitable plugs.
8. Pull off the control unit connector from the control unit.
9. Remove the hydraulic unit (a/f 8) and take out of the bracket ,upwards.
Installing hydraulic unit
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 assembling the hydraulic unit, a static test and a swap test must be carried out with the Porsche System Tester.
-> After assembly of the brake master cylinder or the hydraulic unit, the pressure sensor must be calibrated with the Porsche System Tester.
Note:
^ When fitting the hydraulic connections, the electric plug connections on the control units must remain connected as long as possible. This prevents the plug connections on the hydraulic unit or in the connectors inside from being splashed with brake fluid or water.
^ Any damp connector must be wiped dry before being disconnected from the connector on the hydraulic unit. If necessary, provide the connector with a suitable protector.
^ Brake fluid on electrical contacts (even thinned brake fluid) leads to corrosion and may cause faults in the system.
^ The brake lines must not be bent in the area of the hydraulic unit.
^ Clean the interfacing points of the brake lines, but not with cleaning agents.
^ Rinse off any brake fluid emerging thoroughly with water.
Note:
^ Install in reverse order.
^ Remove the plugs on the new hydraulic unit after the respective brake line is fitted.
^ Pay attention to tightening torques ->47 Tightening torques for brake hydraulic system - see chapter on Technical values'.
1. Bleed the brake system . To ensure the full function of the brake system, drain approximately 250 ccm brake fluid from each wheel.
Porsche System Tester
2. Calibrate the pressure sensor with the ->Porsche System Tester . To do this, select menu >> PSM >> Calibration >> Pressure sensor <<. The security code is displayed in the Porsche System Tester under menu >> PSM >> Actual values <<.
3. The combination sensor (which contains the longitudinal and transverse acceleration sensor) and the steering-angle sensor must then be calibrated. The procedure for this is described in Step 2.
4. Perform a swap test with the Porsche System Tester. To do this, select menu >> PSM > > Function selection >> Drive links <<.
Note: When replacing the hydraulic unit, the connected control mechanism must be coded with the Porsche System Tester (running gear and country coding).
^ To do this, select menu >> PSM >> Function selection >> Coding << and the relevant country. Observe the country coding!
5. Code hydraulic unit.
6. Perform a function test. During the test drive, perform at least one ABS control operation, taking the road conditions into consideration. Read out fault memory. There must not be any stored faults.