Removing and Installing Hydraulic Unit
Removing and installing hydraulic unit
Removal
Information
^ 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!
Information
^ 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 unfavorable 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 center 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.