Hydraulic control unit, removing and installing

Special tools, testers and auxiliary items required

Fig 1: Identifying Torque Wrench V.A.G. 1331

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Torque wrench V.A.G 1331

Fig 2: Identifying Brake Pedal Depressor V.A.G 1869/2

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Brake pedal actuator V.A.G 1869/2
Sealing plugs (repair kit) 1H0 698 311 A

Removing

Location:

Fig 3: Locating Hydraulic Unit

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Hydraulic unit is located on left-hand side of engine compartment.

CAUTION: Brake lines must not be bent.

Note or request radio code on vehicles with coded radio if necessary.
Disconnect battery →
- 27 BATTERY, STARTER, GENERATOR, CRUISE CONTROL
- 27 - BATTERY, STARTER, GENERATOR, CRUISE CONTROL for ELECTRICAL EQUIPMENT - GENERAL INFORMATION

Fig 4: Removing Plenum Chamber Cover

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Remove plenum chamber cover.

Fig 5: Removing Hex Bolts Securing Coolant Expansion Tank & Disconnecting Connector From Coolant Expansion Tank

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Remove hex bolts - 1 - securing coolant expansion tank.
Disconnect connector from coolant expansion tank.

Fig 6: Moving Coolant Expansion Tank Clear To One Side

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Move coolant expansion tank clear to one side.

Fig 7: Brake Pedal Depressor VAG 1869/2 Inserted Between Brake Pedal And Driver's Seat

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Insert brake pedal actuator V.A.G 1869/2 between brake pedal and drivers seat. Depress brake pedal at least 60 mm.
Connect bleeder bottle hose to bleeder screws on left front and left rear brake caliper and open bleeder screws.

NOTE:

The pressure in the hydraulic unit is then released.

Close left front and left rear bleeder screws.
Do not remove brake pedal actuator V.A.G 1869/2.
To protect against escaping brake fluid, place a lint-free rag in the area under the control module and hydraulic unit.

NOTE:

Number brake lines.

CAUTION: Do not bend the brake lines in the area of the hydraulic unit!

Fig 8: Identifying Brake Lines

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Disconnect brake lines between hydraulic unit and brake master cylinder.
Disconnect remaining brake lines - arrows - from hydraulic unit.
Seal brake lines and threaded holes with sealing plugs from repair kit.

Fig 9: Identifying Brake Line Retainer

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Open brake line retainer - 1 -.

Fig 10: Identifying Brake Lines

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Press red locking slide upward.

NOTE:

Make sure that no brake fluid gets into the control module connector housing. This could lead to corrosion of the contacts and thereby cause the system to fail.
Clean a dirty connector housing thoroughly with compressed air.

Release control module connector - arrow - and disconnect.

Fig 11: Pushing Retaining Plate And Disconnecting Connector

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Push retaining plate in direction of - arrow - and disconnect connector.

Fig 12: Removing Hex Bolts

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Remove hex bolts -1-.
Remove hydraulic control unit.

Installing

Installation is in reverse order of removal. Note the following:

NOTE:

Remove sealing plugs on new hydraulic unit when the corresponding brake line is going to be installed.
If the sealing plugs are removed too early, brake fluid can escape, and can no longer be guaranteed that the unit is sufficiently filled or adequately bled.

Fig 13: Connecting Brake Caliper & Piston Circuit Lines

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Connect lines as previously marked:

1 - To right front brake caliper

2 - To left rear brake caliper

3 - To right rear brake caliper

4 - To left front brake caliper

5 - To primary piston circuit

6 - To secondary piston circuit

Install connector on hydraulic pump.
Clip ABS unit onto bracket.

NOTE:

Do not tighten bolts completely. This will make attaching the individual brake lines easier.

After tightening brake lines, tighten hydraulic unit.
Remove brake pedal depressor V.A.G 1869/2.
Bleed brake system → Brake system, bleeding .
Code ABS control module J104. Code control unit using VAS 5051 via Guided fault finding function.

When replacing the control module, select function "Replacing" for the respective control module in the "Guided fault finding".

For this, use vehicle diagnosis, testing and information system VAS 5051.

After fastening the brake lines to the hydraulic unit, perform final control diagnosis Vehicle diagnostic, testing and information system. VAS 5051

NOTE:

Final control diagnosis can be used to establish whether line connections have been interchanged → ABS system components on front axle, removing and installing .

Tightening torques

Component	Nm
Brake lines to hydraulic unit M10 (brake line diameter 5 mm)	12
Brake lines to hydraulic unit M12 (brake line diameter 5 mm)	12
Brake lines to hydraulic unit M12 (brake line diameter 8 mm)	16