Procedures

Removing And Installing Hydraulic Unit

Removal







NOTE: For the removal and installation of the hydraulic unit -D- the brake master cylinder -B- and the brake booster -C- remain mounted (installed).







1. Switch off ignition. Remove cover -A- from the hydraulic unit/brake unit.
2. Hold down brake pedal with pedal holder, so that the brake fluid does not run out of the expansion tank completely.
3. To remove the hydraulic unit -D-, carry out the following removal procedure:







- Undo the brake lines on the hydraulic unit.
- Remove the lines between the brake master cylinder intermediate piston circuit and the hydraulic unit.
- Close the brake lines and the brake line connections with suitable plugs.
- Disconnect plug from pressure sensor (vehicles with PSM).
- Unlock/disconnect the control module connector on the hydraulic unit. Cover the plug connection and the plug.

NOTE:
- In the case of assembly work on the hydraulic connections, the electrical plug connections on the hydraulic unit must always be connected.
- This prevents the plug connections on the hydraulic unit or in the plugs inside from being splashed with brake fluid or water.
- Any damp plug must be wiped dry before being disconnected from the plug on the hydraulic unit.
- Brake fluid on electrical contacts (even thinned brake fluid) leads to corrosion and may cause faults in the system.
- Undo and guide out the hydraulic unit. In the case of unfavourable tolerances, remove the hydraulic unit without the bracket for the hydraulic unit.

Installation
1. Install in reverse order.
- First connect the electrical plug connections on the hydraulic unit, so that the plug connections inside or on the hydraulic unit can not be splashed with brake fluid or water.
- After bleeding, check the assignment of the brake lines/solenoid valves to the correct brake calipers. Also carry out a system check or a swap test with the PST 2 (Swap test menu item for vehicles with PSM).

2. Bleed brakes.
- Pay attention to the following in the case of vehicles with ABS/TC (Traction Control) or PSM (recognisable by the rocker switch in the centre console):
- First bleed brakes as usual.
- In the case of vehicles with ABS/TC (Traction Control), bleed the ABD circuit after the usual bleeding procedure. This is carried out with the return pump running (activation with the Porsche System Tester) 'on rear right-hand bleeder valve'.
- In the case of vehicles with PSM, after the usual bleeding procedure, 'bleed at front right-hand bleeder valve' with booster pump running (activation with Porsche System Tester).

3. When replacing the hydraulic unit in vehicles with ABS/TC or PSM (4-channel system), code the control module (manual transmission or Tiptronic).
4. Carry out the following tests:







- Check the system (brake lines and connections) for leaks.
- Read out and erase the fault memory of the control module with the Porsche System Tester 2 (PST 2). Also carry out the 'static test'.
- Check electrical and hydraulic lines (brake lines) for incorrect assignment using the PST 2 (carry out a system check or a swap test).
- Then start the engine. The ABS, ABS/TC or PSM-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 fault memory again. There must not be any stored faults.