Brake systems · Anti-lock brake system · Assembly overview – hydraulic unit, brake booster/brake master cylinder
Bosch 8.2i; 9.0i ABS/EDL/TCS/ESP, RHD vehicles
- 1 Brake line
- ABS hydraulic unit - N55- to front right brake caliper.
- Marking on ABS hydraulic unit - N55- -VR-
- With thread M10 x 1
- 2 Brake line
- ABS hydraulic unit - N55- to rear left brake caliper/wheel brake cylinder.
- Marking on ABS hydraulic unit - N55- -HL-
- With thread M10 x 1
- 3 Brake line
- ABS hydraulic unit - N55- to rear right brake caliper/wheel brake cylinder.
- Marking on ABS hydraulic unit - N55- -HR-
- With thread M12 x 1
- 4 Brake line
- ABS hydraulic unit - N55- to front left brake caliper.
- Marking on ABS hydraulic unit - N55- -VL-
- With thread M12 x 1
- 5 ABS control unit - J104-
- Removing and installing ABS hydraulic unit - N55- with ABS control unit - J104- ⇒ 6.4.2 Removing control unit and hydraulic unit.
- 6 Nut
- 8 Nm
- For rubber damper mounting
- Qty. 3
- 1 cap nut on side at top; it must be unscrewed to height of stud shoulder, otherwise removal and installation are not possible.
- 2 hexagon nuts with washer at bottom; turn back until rubber dampers can be turned.
- 7 ABS hydraulic unit - N55-
- ABS return flow pump - V39- and valve block should not be separated from each other
- When replacing the ABS hydraulic unit - N55-, always seal the old part with plugs - 1H0 698 311 A-.
- Removing and installing ABS hydraulic unit - N55- with ABS control unit - J104- ⇒ 6.4.2 Removing control unit and hydraulic unit.
- 8 Nut
- 25 Nm
- Qty. 3
- Always renew after removing.
- 9 Bracket
- 10 Brake booster
- Removing and installing ⇒ 7 Removing and installing brake booster.
- 11 Brake line
- ABS hydraulic unit - N55- to brake master cylinder/secondary piston circuit
- Marking on ABS hydraulic unit - N55- -HZ1-
- With thread M12 x 1
- 12 Brake line
- ABS hydraulic unit - N55- to brake master cylinder/secondary piston circuit
- Marking on ABS hydraulic unit - N55- -HZ2-
- With thread M12 x 1
- 13 Brake line
- From primary piston circuit of brake master cylinder to ABS hydraulic unit - N55-.
- Marking on ABS hydraulic unit - N55- -HZ1-
- With thread M12 x 1
- 14 Brake line
- Brake master cylinder/secondary piston circuit to ABS hydraulic unit - N55-.
- Marking on ABS hydraulic unit - N55- -HZ2-
- With thread M12 x 1
6.4.1 Connecting brake lines from brake master cylinder to ABS hydraulic unit - N55-
On brake master cylinder:
A - Primary piston circuit of brake master cylinder to ABS hydraulic unit - N55-.
B - Secondary piston circuit of brake master cylinder to ABS hydraulic unit - N55-.
- 4 ABS hydraulic unit - N55- to front right brake caliper.
To ABS hydraulic unit - N55- :
A - ABS hydraulic unit - N55- to primary piston circuit of brake master cylinder
- Marking on ABS hydraulic unit - N55- -HZ1-
B - ABS hydraulic unit - N55- to secondary piston circuit of brake master cylinder
- Marking on ABS hydraulic unit - N55- -HZ2-
- 1 ABS hydraulic unit - N55- to rear left brake caliper/wheel brake cylinder.
- Marking on ABS hydraulic unit - N55- -HL-
- 2 ABS hydraulic unit - N55- to rear right brake caliper/wheel brake cylinder.
- Marking on ABS hydraulic unit - N55- -HR-
- 3 ABS hydraulic unit - N55- to front left brake caliper.
- Marking on ABS hydraulic unit - N55- -VL-
- 4 ABS hydraulic unit - N55- to front right brake caliper.
- Marking on ABS hydraulic unit - N55- -VR-
6.4.2 Removing control unit and hydraulic unit
Special tools and workshop equipment required
- Torque wrench - V.A.G 1331-
- Brake pedal depressor - V.A.G 1869/2-
Sealing plug - 1H0 698 311 A-
After removing ABS control unit - J104- and ABS hydraulic unit - N55-, fit the transport protection.
Without transport protection, the warranty for the ABS hydraulic unit - N55- will not be recognised.
- 1 Transport protection for contact pins (foam)
- 2 M10 sealing plugs
- 3 M12 sealing plugs
Removing
Location:
The ABS control unit - J104- is bolted to the ABS hydraulic unit - N55- and is located on the left in the engine compartment.
- 1 Brake booster with tandem brake master cylinder
- 2 ABS control unit - J104- with ABS hydraulic unit - N55-
- Read out and make a note of the code of ABS control unit - J104- ⇒ 3 Connecting -VAS 5051- and selecting functions.
- Disconnect battery ⇒ Electrical system; Rep. gr. 27.
- Remove air filter housing ⇒ Rep. gr. 24; Fuel mixture, electronic injection, gas.
Vehicles with battery in engine compartment
- Remove battery and battery tray ⇒ Electrical system; Rep. gr. 27.
Continuation for all vehicles
- Press locking slide -2- downwards in -direction of arrow-.
- Disengage locking clamp to -1- release connector -3- of ABS control unit - J104-.
- To do this, press locking clamp -1- downwards in -direction of arrow-.
- Pull connector -3- off forwards.
- Apply brake pedal depressor - V.A.G 1869/2-.
- Connect bleed bottle bleed hose -1- to bleed valve of front left brake caliper.
- Open bleed valve.
- Connect bleed bottle bleed hose -1- to bleed valve of rear left brake caliper/wheel brake cylinder.
- Open bleed valve.
- Depress brake pedal at least 60 mm using brake pedal depressor - V.A.G 1869/2-.
- Close front left and rear left bleeder valve.
- Do not remove brake pedal depressor - V.A.G 1869/2-.
- Place sufficient lint-free cloths under the ABS hydraulic unit - N55-.
Ensure no brake fluid gets onto contacts.
- First identify the two brake master cylinder brake lines -A- and
- B- and unscrew from ABS hydraulic unit - N55-.
- Immediately seal brake lines and threaded holes with sealing plugs - 1H0 698 311 A-.
- Mark and unscrew brake lines -1- to -4-.
- Immediately seal brake lines and threaded holes with sealing plugs - 1H0 698 311 A-.
- Loosen the 3 nuts -arrows- of rubber damper mounting until the rubber dampers can be turned.
- Undo upper nut on side as far as shoulder of the stud bolt.
- Pull ABS hydraulic unit - N55- -1- together with ABS control unit - J104- upwards out of the bracket in -direction of arrow-.
6.4.3 Unscrewing control unit from hydraulic unit
Special tools and workshop equipment required
- ESD workplace - VAS 6613-
- If a control unit is defective, the control unit must be disconnected from the hydraulic unit and only the control unit renewed.
- If the hydraulic unit is defective, the hydraulic unit must be renewed together with the control unit.
This electrostatic charge can cause malfunctions if you touch electric components.
- Before working on electric components, touch an earthed object, ESD workplace - VAS 6613-. Do not directly touch connector contacts or electronic components.
- Set hydraulic unit with control unit on top on ESD workplace - VAS 6613-.
- Remove external Torx screws -arrows- from control unit.
- Taking care not to cant control unit, pull it off hydraulic unit.
- Cover solenoids of control unit with a lint-free cloth.
- Check cleanliness of hydraulic unit sealing surface; clean with methylated spirits and a lint-free cloth if necessary.
Hydraulic unit sealing surface must not be processed with a file, metal scraper, sandpaper or similar.
If hydraulic unit sealing surface is damaged (e.g. scoring, scratches), hydraulic unit must be renewed together with control unit.
After separating control unit and hydraulic unit, use transport protection for contact pins.
- If a control unit is defective, the control unit must be disconnected from the hydraulic unit and only the control unit renewed.
- If the hydraulic unit is defective, the hydraulic unit must be renewed together with the control unit.
6.4.4 Installing new control unit
Special tools and workshop equipment required
- ESD workplace - VAS 6613-
- Torque screwdriver - V.A.G 1624-
- External Torx bit E6
- Without canting it, place control unit onto hydraulic unit.
- Tighten hydraulic unit and control unit diagonally in three stages to specified torque with enclosed new Torx bolts.
The hydraulic unit's threads for securing the control unit must not be recut. If the threads are damaged (bolts difficult to turn in by hand or cannot be tightened to the specified torque), hydraulic unit must be renewed.
Specified torque in three stages:
Use new bolts! Stage 1: position and centre control unit; screw in - Torx bolts until Torx bolts contact housing. Stage 2: Seat sealing lugs evenly on all sides and 1.5 to tighten initially.
2 Nm
Stage 3: Final tightening to specified torque. 3 Nm
6.4.5 Installing control unit and hydraulic unit
Install in reverse order. Note the following points:
- Remove brake pedal depressor - V.A.G 1869/2-.
- Bleed brake system ⇒ 4 Bleeding brake system.
After the ABS control unit - J104- and the ABS hydraulic unit - N55- have been installed, the steering angle sender - G85-, the lateral acceleration sender - G200- and the brake pressure sender - G201- must be reset ⇒ 3 Connecting -VAS 5051- and selecting functions.
If a new ABS control unit - J104- has been installed, it must be coded ⇒ 3 Connecting -VAS 5051- and selecting functions.
Specified torque
| Component | Specified torque |
|---|---|
| Bolt for ABS hydraulic unit - N55- to bracket. | 8 Nm |
| Brake lines to ABS hydraulic unit - N55- Thread M10 x 1 | 14 Nm |
| Thread M12 x 1 | 14 Nm |