Bleeding brake system when brake fluid reservoir was empty — VW

The following description deals with the Audi TT 1999 ä. Therefore differences must be considered, if necessary.

Special tools and workshop equipment required

Brake charge and bleed equipment VAS 5234

or

Brake charge and bleed equipment V.A.G 1869 A

Vehicle diagnostic, testing and information system VAS 5051 and VAS 5051/1

When using a brake system filling and bleeding appliance (such as VAS 5234 or V.A.G 1869 A) to replenish the brake fluid, make sure that filling pressure does not exceed 1 bar.

If the filling pressure exceeds 1 bar, a hydraulically controlled change-over valve (which is required for the EDL function) prevents unrestricted flushing of the EDL-related parts of the hydraulic unit. If this is the case, it may not be possible to bleed the system properly.

For this reason the brake fluid pressure must be reduced to 1 bar on the brake filling and bleeding appliance.

=> Operating instructions for VAS 5234 and V.A.G 1869 A

Filler and bleeder unit V.A.G 1238/B is not suitable for bleeding the brake system by using the "Basic setting" function.

If only filler and bleeder unit V.A.G 1238/B is available, then switch unit on/off to ensure that sufficient brake fluid is always present in reservoir.

Requirement for test:

Connect vehicle diagnostic, testing and information system VAS 5051, select "Vehicle self-diagnosis" and vehicle system "03 - Brake electronics".

=> Running gear, Self-diagnosis; Repair group 01
Running gear, Self-diagnosis

Pre-bleeding of brake system

Connect brake system filling and bleeding appliance VAS 5234 or V.A.G 1869 A.
Open bleeder screws in the specified sequence and pre-bleed brake calipers.

1 -
Bleed front left and front right brake calipers simultaneously.
2 -
Bleed rear left and rear right brake calipers simultaneously.

Leave the bleed screw open, with brake fluid hose connected, until brake fluid free from air bubbles comes out of the bleed screw.

Bleeding

Display on VAS 5051:

Select the diagnosis function "04 - Basic settings" from the menu -1-.

Note:

During the next steps the ABS warning lamp flashes.

Display on VAS 5051:

1 -
Enter display group

Using the keypad -2-, enter "001" to select Display group 001 and confirm entry with Q key.

Display on VAS 5051:

1 -
System in basic setting
2 -
Display group 1
3 -
Press pedal and hold in position ...

Operate pedal with substantial foot pressure and hold.
Pedal sags, hydraulic pump starts up, pedal returns

Display on VAS 5051:

3 -
Release pedal; FR/FL bleed screws OPEN <>

Release pedal, open front bleed screws.

Press the s button to advance to Display group 002.

Display on VAS 5051:

1 -
System in basic setting
2 -
Display group 2
3 -
Please wait .. (10 sec.)

Wait for 10 seconds.
Hydraulic pump starts up briefly

Display on VAS 5051:

3 -
Press pedal 10X; bleed screws CLOSED <>

Press pedal 10 times, close front bleed screws.

Press the s button to advance to display group 003.

Display on VAS 5051:

1 -
System in basic setting
2 -
Display group 3
3 -
Press pedal and hold in position ...

Repeat bleeding procedure as described above
Press the s button several times to advance to the next display groups until display group 17 is indicated.

Display on VAS 5051:

1 -
System in basic setting
2 -
Display group 17
3 -
Partial bleeding over ...

Press the ◂ button to exit from diagnosis function "04 - Basic settings".

Display on VAS 5051:

Select diagnosis function "06 - End output" from the menu -1-.

Display on VAS 5051:

When this display appears, switch off ignition and unplug diagnostic connector.
Now perform bleeding of brake system => Page
47-17
.

Special point with right-hand drive vehicles:

Brake master cylinder must be bled via bleed screws -arrows- after completion of basic settings if one chamber in the brake fluid reservoir has run completely dry.