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Home >> BMW >> 1998 >> 750iL >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Brakes - Repair Instructions >> Mechanical - Hydraulic Control Unit >> 34 51 520 Removing and installing / replacing ABS hydraulic control unit

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

NOTE: Note "General Information", Refer to 34 00... GENERAL DATA 
CAUTION: After finishing work:
Check function of hydraulic control unit.

Installation: 

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

Switch off ignition.

Disconnect battery negative lead.

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
G03213727

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

NOTE: Keep brake fluid out of cable connector.
Fig 2: Identifying Central Connector
G03213728

Unfasten brake lines.

CAUTION: Do not mix up brake lines, mark before removing if necessary.

Installation: 

  1. Line connections
  2. (F) from THZ circuit F to hydraulic control unit circuit F (front-axle circuit)
  3. (R) from THZ circuit R to hydraulic control unit circuit R (rear-axle circuit)
  4. (FR) from hydraulic control unit FR to front right wheel brake
  5. (FL) from hydraulic control unit FL to front left wheel brake
  6. (RA) from hydraulic control unit RA to rear-axle wheel brake

Tightening torque. Refer to BRAKES - TIGHTENING TORQUES

Fig 3: Identifying Line Connections
G03213729

Unfasten screw and remove hydraulic control unit.

Fig 4: Unfastening Screw & Removing Hydraulic Control Unit
G03213730