34 51 520 Removing and installing / replacing ABS hydraulic control unit: Installation:

Bleeding brake system, refer to 34 00 047 BLEEDING BRAKE SYSTEM WITH ABS 

Switch off ignition.

Disconnect battery negative lead, refer to INSTRUCTIONS FOR DISCONNECTING AND CONNECTING BATTERY .

Draw brake fluid out of expansion tank with a suction bottle reserved for exclusive use with brake fluid.

Fig 1: Drawing Brake Fluid Out Of Expansion Tank With A Suction Bottle

Unlock central connector (1) and pull off. Unfasten nut (2) and remove ground wire.

Fig 2: Identifying Central Connector

Unfasten brake lines.

Line connections

(F) from THZ circuit F to hydraulic control unit circuit F (front axle circuit)

(R) from THZ circuit R to hydraulic control unit circuit R (rear axle circuit)

(FR) from hydraulic control unit FR to front right wheel brake

(FL) from hydraulic control unit FL to front left wheel brake

(RA) from hydraulic control unit RA to rear-axle wheel brake

Fig 1: Identifying Line Connections

Tightening torque, refer to 34 32 1AZ BRAKE LINES

Unfasten screw and remove hydraulic control unit.

Fig 2: Unfastening Screw