45 - 5
Hydraulic unit, brake booster/brake master cylinder, assembly overview
ABS Bosch 5.3 up to model year 1999 - Vehicles up to VIN 3B X 600 000
With the following versions: ABS; ABS/EDL and ABS/EDL/ASR
Brake booster
On gasoline engines the vacuum required is taken from the intake manifold.
To produce vacuum with diesel engines, a vacuum pump is equipped.
Functional check:
Page 1 / 49 Volkswagen Passat B5 - Hydraulic unit, brake booster/brake master cylinder
Removing and installing 47-8, Brake booster, removing and installing (Vehicles up to model year 1999)
Spring
Self-locking nut, 9 Nm
Threaded stud
Rubber bushing
Control module
Removing and installing separately 45-5, ABS Control Module, removing and installing separately
Remove and install together with hydraulic unit 45-5, Control module and hydraulic unit, removing and installing
T 20 torx socket head bolt, 8 Nm
ABS hydraulic unit
Note different versions:
ABS Front Wheel Drive (FWD)
ABS/EDL front and All
- With engine switched off, depress brake pedal firmly several times (to exhaust the vacuum in the unit).
- Depress brake pedal with average foot pressure, hold and start engine. If the booster unit is working properly, the pedal will be felt to give slightly under foot (booster assist becomes effective).
- If faulty, replace completely.
Page 2 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Wheel Drive (AWD) 45-5, Connecting tandem brake master cylinder to hydraulic unit for ABS/EDL front and all wheel drive, as well as ABS/EDL/ASR front wheel drive
ABS/EDL/ASR Front Wheel Drive (FWD) 45-5, Connecting tandem brake master cylinder to hydraulic unit for ABS/EDL front and all wheel drive, as well as ABS/EDL/ASR front wheel drive
Removing and installing 45-5, Control module and hydraulic unit, removing and installing
Brake line connection
Hydraulic unit to right front brake caliper
Brake line connection
Hydraulic unit to left front brake caliper
Brake line
Brake master cylinder/secondary piston circuit to hydraulic unit
Brake line
Brake master cylinder/primary piston circuit to hydraulic unit
Brake line connection
Hydraulic unit to left rear brake caliper
Brake line connection
Page 3 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Hydraulic unit to right rear brake caliper
Bracket
Hex head bolt, 9 Nm
Bracket
T 45 torx socket head bolt, 25 Nm
Self-locking hex nut, 49 Nm
Tandem brake master cylinder
With seal
Cap
Brake fluid reservoir
Connecting brake lines from tandem master cylinder to ABS hydraulic unit
A - Secondary piston circuit
B - Primary piston circuit
1 - Hydraulic unit to left rear brake caliper
2 - Hydraulic unit to right rear brake caliper
3 - Hydraulic unit to right front brake caliper
4 - Hydraulic unit to left front brake caliper
Page 4 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Connecting tandem brake master cylinder to hydraulic unit for ABS/EDL front and all wheel drive, as well as ABS/EDL/ASR front wheel drive
A - Secondary piston circuit
B - Primary piston circuit
1 - Hydraulic unit to left rear brake caliper
2 - Hydraulic unit to right rear brake caliper
3 - Hydraulic unit to right front brake caliper
4 - Hydraulic unit to left front brake caliper
ABS Control Module, removing and installing separately
Special tools, testers and auxiliary items required
Torque Wrench (5-60 Nm) VAG1783
- For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary.
- Disconnect battery.
- Remove left front wheel.
Page 5 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Remove left front wheel housing liner
.
Repair Manual, Body Exterior, Repair Group 66, Wheel housing liner
- Loosen power steering fluid reservoir.
- Remove tank for windshield washer system
.
Repair Manual, Electrical Equipment, Repair Group 92, Windshield washer system
- Thoroughly clean control module, hydraulic unit and surrounding area.
- Vacuum clean control module, hydraulic unit and surrounding area in order to prevent dirt and moisture from entering the unit.
- Disengage connector - arrow 1 - and disconnect - arrow 2 - from control module.
Page 6 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Disengage and disconnect harness connector - 1 - .
- Remove bolts - 1 - and pull control module - 2 - off hydraulic unit without canting.
- Clean sealing surface - 2 - using plastic scraper - 1 - enclosed.
- Check valves - 3 - for damage.
Note:
Do not use aggressive cleaning agents (use cleaning agent enclosed).
Check sealing surface for damage (visual check).
Caution!
No moisture or particles of dirt must penetrate in interior of control module.
If sealing surface or contact tags are damaged, hydraulic unit must be replaced.
Excessive shaking (e.g. dropping, impact) may destroy the control module. Control module must then no longer be used.
Page 7 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Carefully slide control module - 1 - onto hydraulic unit - 2 - . Make sure valves do not cant.
- Control module housing edge must glide over offset on hydraulic unit.
Note:
Use new bolts.
A new control module may be assembled on an already used hydraulic unit a maximum of two times in order to guarantee the seal of the elastic gaskets.
A control module which was once in driving operation must not be installed a second time.
- Press control module onto hydraulic unit and install new bolts - 1 and 2 - evenly (do not tighten) until control module makes contact evenly on hydraulic unit.
- Install bolts - 1 to 6 - until making contact, do not tighten.
- Now tighten bolts in the specified sequence to tightening torque of 2.5 Nm.
Page 8 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Install harness connector - 1 - .
- Code radio.
- If control module is codeable, code control module Coding control module using Vehicle Diagnosis, Testing and Information System VAS 5051 , via "Guided Fault Finding" .
Tightening torque: Control module to hydraulic unit 2.5 Nm
Control module and hydraulic unit, removing and installing
Special tools, testers and auxiliary items required
Torque wrench V.A.G 1331
Page 9 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Brake pedal loading device V.A.G 1869/2
Location:
The control module is bolted to the hydraulic unit and is located in the engine compartment, on the left side.
Warning!
Do not bend the brake lines in the area of the hydraulic unit!
Removing
- Note or request radio code on vehicles with coded radio if necessary.
- Disconnect battery.
- Release control module connector - arrow 1 - and pull off - arrow 2 - .
- Connect bleeder bottle hose to left front brake caliper bleeder screw and open bleeder screw.
- Install brake pedal loading device V.A.G 1869/2 .
- Depress brake pedal with brake pedal loading device V.A.G 1869/2 .
Page 10 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Close left front bleeder screw.
- Place sufficient lint-free cloths under control module and hydraulic unit.
- Disconnect brake lines from the hydraulic unit.
- Plug brake lines and threaded holes with sealing plugs from the repair kit Part No. 1H0 698 311 A.
- Remove nuts on hydraulic unit bracket - arrows - .
- Remove hydraulic unit with control module.
Installing
Note:
Remove sealing plugs on new hydraulic unit when the corresponding brake line is going to be connected.
If the sealing plugs are removed too early, brake fluid can escape, and can no longer be guaranteed that the unit is filled or adequately bled.
- Installation is in reverse order of removal.
- Bleeding brake system 47-4, Braking system, bleeding .
- Enter radio code.
- If control module can be coded, then code control module Coding the control module with the Vehicle diagnostic,
test and information system. in "Guided Fault Finding"
Tightening torques: Brake lines to ABS module: Thread M 10 x 1 14 Nm
Page 11 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Thread M 12 x 1 14 Nm
Hydraulic unit hex to bracket Item - 3 -
ABS Bosch 5.3 from model year 2000 - Vehicles from VIN 3B Y 000 001
With the following versions: ABS; ABS/EDL and ABS/EDL/ASR
Tandem brake booster
On gasoline engines the vacuum required is taken from the intake manifold.
As of model year 2001, vehicles with a gasoline engine and automatic transmission are equipped with a brake vacuum pump
47-6, Brake system vacuum pump V192 .
Page 12 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
To produce vacuum with diesel engines, a vacuum pump is equipped.
Functional check:
Removing and installing 47-8, Brake booster, removing and installing (vehicles as of model year 2000)
Brake line connection
To left rear brake caliper
Marked on hydraulic unit with "HL"
Brake line connection
To right rear brake caliper
Marked on hydraulic unit with "HR"
Brake line
Brake master cylinder/secondary piston circuit to hydraulic unit
Brake line
- With engine switched off, depress brake pedal firmly several times (to exhaust the vacuum in the unit).
- Depress brake pedal with average foot pressure, hold and start engine. If the booster unit is working properly, the pedal will be felt to give slightly under foot (booster assist becomes effective).
- If faulty, replace completely.
Page 13 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Brake master cylinder/primary piston circuit to hydraulic unit
Brake line
To left front brake caliper
Marked on hydraulic unit with "VL"
Hex nut, 12 Nm
Threaded stud
Rubber bushing
Control module and hydraulic unit
Control Module, removing and installing separately 45-5, ABS Control Module, removing and installing separately
Control module and hydraulic unit, removing and installing 45-5, Control module and hydraulic unit, removing and installing
Brake line
To right front brake caliper
Marked on hydraulic unit with "VR"
Bracket
Hex head bolt, 9 Nm
Bracket
Application Parts Catalog
Rubber bushing
Hex head bolt
Page 14 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Tandem master cylinder
Cannot be repaired. If faulty, replace.
Removing and installing 47-7, Brake master cylinder, removing and installing (Vehicles as of model year 2000)
T 45 torx socket head bolt, 25 Nm
Self-locking nut, 49 Nm
Sealing plug
Moisten with brake fluid and press into brake fluid reservoir
Brake fluid reservoir
Sealing ring
Cap
Vacuum hose
Insert into brake booster unit
Seal ring
Connecting tandem master cylinder brake lines to hydraulic unit for ABS/EDL front and all wheel drive (AWD), as well as ABS/EDL/ASR front wheel drive (FWD)
Page 15 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
A - Secondary piston circuit
B - Primary piston circuit
1 - Hydraulic unit to left rear brake caliper
2 - Hydraulic unit to right rear brake caliper
3 - Hydraulic unit to right front brake caliper
4 - Hydraulic unit to left front brake caliper
ABS Control Module, removing and installing separately
Special tools, testers and auxiliary items required
Torque wrench V.A.G 1783
- For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary.
- Disconnect battery.
- Remove left front wheel.
- Remove left front wheel housing liner
.
Repair Manual, Body Exterior, Repair Group 66, Wheel housing liner
- Loosen power steering fluid reservoir.
- Remove tank for windshield washer system
Repair Manual, Electrical Equipment, Repair Group 92, Windshield washer system
Page 16 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
.
- Thoroughly clean control module, hydraulic unit and surrounding area.
- Vacuum clean control module, hydraulic unit and surrounding area in order to prevent dirt and moisture from entering the unit.
- Disengage connector - arrow 1 - and disconnect - arrow 2 - from control module.
- Disengage and disconnect harness connector - 1 - .
- Remove bolts - 1 - and pull control module - 2 - off hydraulic unit without canting.
Page 17 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Clean sealing surface - 2 - using plastic scraper - 1 - enclosed.
- Check valves - 3 - for damage.
Note:
Do not use aggressive cleaning agents (use cleaning agent enclosed).
Check sealing surface for damage (visual check).
Caution!
No moisture or particles of dirt must penetrate in interior of control module.
If sealing surface or contact tags are damaged, hydraulic unit must be replaced.
Excessive shaking (e.g. dropping, impact) may destroy the control module. Control module must then no longer be used.
- Carefully slide control module - 1 - onto hydraulic unit - 2 - . Make sure valves do not cant.
- Control module housing edge must glide over offset on
Page 18 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
hydraulic unit.
Note:
Use new bolts.
A new control module may be assembled on an already used hydraulic unit a maximum of two times in order to guarantee the seal of the elastic gaskets.
A control module which was once in driving operation must not be installed a second time.
- Press control module onto hydraulic unit and install new bolts - 1 and 2 - evenly (do not tighten) until control module makes contact evenly on hydraulic unit.
- Install bolts - 1 to 6 - until making contact, do not tighten.
- Now tighten bolts in the specified sequence to tightening torque of 2.5 Nm.
- Install harness connector - 1 - .
- Code radio.
Page 19 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- If control module is codeable, code control module Coding control module using Vehicle Diagnosis, Testing and Information System VAS 5051 , via "Guided Fault Finding" .
Tightening torque: Control module to hydraulic unit 2.5 Nm
Control module and hydraulic unit, removing and installing
Special tools, testers and auxiliary items required
Torque wrench V.A.G 1331
Brake pedal loading device V.A.G 1869/2
If the hydraulic unit is faulty the whole assembly must be replaced. If the control module is faulty it can be replaced separately from the hydraulic unit.
Location:
The control module is bolted to the hydraulic unit and is located in the engine compartment, on the left side.
Warning!
Page 20 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Do not bend the brake lines in the area of the hydraulic unit!
Removing
- Note or request radio code on vehicles with coded radio if necessary.
- Disconnect battery.
- Release control module connector - arrow 1 - and pull off - arrow 2 - .
- Connect bleeder bottle hose to left front brake caliper bleeder screw and open bleeder screw.
- Install brake pedal loading device V.A.G 1869/2 .
- Depress brake pedal with brake pedal loading device V.A.G 1869/2 .
- Close left front bleeder screw.
- Place sufficient lint-free cloths under the control module and hydraulic unit.
- Detach brake lines from the hydraulic unit.
- Plug brake lines and threaded holes with sealing plugs from the repair kit Part No. 1H0 698 311 A.
Page 21 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Unfasten nuts on hydraulic unit bracket - arrows - .
- Remove hydraulic unit with control module.
Installing
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 filled or adequately bled.
- Further Installation is in reverse order of removal.
- Bleed brake system 47-4, Braking system, bleeding .
- Enter radio code.
- Perform control module coding Coding the control module with the Vehicle diagnostic, test and information system. in "Guided Fault Finding"
Tightening torques: Brake lines to ABS module: Thread M 10 x 1 14 NmThread M 12 x 1 14 Nm
Hydraulic unit nut to bracket Item - 7 -
ABS/EDL/ASR/ESP Bosch 5.3, assembly overview, up to model year 1999 - Vehicles up to VIN 3B X 600 000
Page 22 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Tandem master cylinder
With seal
Self-locking nut, 49 Nm
Cap
Brake fluid reservoir
Brake line
Brake master cylinder/primary piston circuit to hydraulic pump for traction control
Identification on the hydraulic pump for traction control "HZ"
Page 23 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Brake booster
On gasoline engines the vacuum required is taken from the intake manifold.
To produce vacuum with diesel engines, a vacuum pump is equipped.
Functional check:
Removing and installing 47-8, Brake booster, removing and installing (Vehicles up to model year 1999)
Brake line connection
To left rear brake caliper
Marked on hydraulic unit with "HL"
Brake line connection
To right rear brake caliper
Marked on hydraulic unit with "HR"
Rubber bushing
Hex head bolt, 9 Nm
- With engine switched off, depress brake pedal firmly several times (to exhaust the vacuum in the unit).
- Depress brake pedal with average foot pressure, hold and start engine. If the booster unit is working properly, the pedal will be felt to give slightly under foot (booster assist becomes effective).
- If faulty, replace completely.
Page 24 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Brake line
Brake master cylinder/secondary piston circuit to hydraulic unit
Marked on hydraulic unit with "HZ2"
Brake line
Hydraulic unit to hydraulic pump for traction control
Marked on hydraulic unit with "VLP"
Identification on the hydraulic pump for traction control "HE"
Brake line
To left front brake caliper
Marked on hydraulic unit with "VL"
Hex nut
8 mm with 12 Nm
6 mm with 9 Nm
Threaded stud
Brake line
To right front brake caliper
Marked on hydraulic unit with "VR"
ABS hydraulic unit
Bracket
Bracket
Hydraulic pump for traction control
Page 25 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Brake pressure sensor
Always replace together with the hydraulic pump for traction control.
Connection for brake fluid from brake fluid reservoir
Identification on the hydraulic pump for traction control "BA"
Connection for the hydraulic pump for traction control
Torx socket head bolt T45, 25 Nm
Connection of brake lines from tandem master cylinder and the hydraulic pump for traction control to the hydraulic unit for ABS/EDL/ASR and ESP
A - Hydraulic unit to hydraulic pump for traction control
- Marked on hydraulic unit with VLP
- Identification on the hydraulic pump for traction control HE
B - Hydraulic unit to master cylinder secondary piston circuit
- Marked on hydraulic unit with HZ2
1 - Hydraulic unit to left front brake caliper
- Marked on hydraulic unit with VL
2 - Hydraulic unit to right front brake caliper
Page 26 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Marked on hydraulic unit with VR
3 - Hydraulic unit to right rear brake caliper
- Marked on hydraulic unit with HR
4 - Hydraulic unit to left rear brake caliper
- Marked on hydraulic unit with HL
ABS Hydraulic Unit N55 with Hydraulic pump for traction control V156 , removing and installing
Special tools, testers and auxiliary items required
Torque wrench V.A.G 1331
Brake pedal loading device V.A.G 1869/2
Page 27 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
The ABS hydraulic unit N55 and the hydraulic pump for traction control V156 are located in left side of engine compartment.
1 - Hydraulic unit with ABS return flow pump
The hydraulic unit and ABS return flow pump form one unit and must always be replaced together if malfunction exists.
2 - Hydraulic pump for traction control with brake pressure sensor.
The hydraulic pump for traction control and the brake pressure sensor form one unit and must always be replaced together if malfunction exists.
Warning!
Do not bend the brake lines in the area of the hydraulic unit!
Removing
- Note or request radio code on vehicles with coded radio if necessary.
- Disconnect battery.
Page 28 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Release hydraulic unit connector - arrow 1 - and pull off - arrow 2 - .
- Install brake pedal loading device V.A.G 1869/2 .
- Depress brake pedal with brake pedal loading device V.A.G 1869/2 .
- Connect bleeder bottle hose to left front brake caliper bleeder screw and open bleeder screw.
- Close left front bleeder screw.
- Place sufficient lint-free cloths under hydraulic unit.
Make sure no brake fluid gets onto contacts.
These procedures are only for removing the hydraulic unit.
- Detach brake lines from the hydraulic unit.
- Plug brake lines and threaded holes with sealing plugs from repair kit Part No. 1H0 698 311 A.
- Remove nuts on hydraulic unit bracket - arrows - .
- Remove hydraulic unit with control module.
These procedures are for removing the hydraulic unit
Page 29 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
and the hydraulic pump for traction control
- Remove power steering fluid reservoir - 1 - and set aside with hoses connected.
- Remove coolant reservoir - 2 - and set aside with coolant hoses connected.
- Remove brake lines to the hydraulic unit and hydraulic pump for traction control.
- Disconnect connector from hydraulic pump for traction control.
- Remove brake fluid supply hose from hydraulic pump for traction control.
- Plug brake lines and threaded holes with sealing plugs from repair kit Part No. 1H0 698 311 A.
- Remove bolts on hydraulic unit bracket
- Remove hydraulic unit with traction control hydraulic pump upward.
Installing
Note:
Remove sealing plugs on new hydraulic unit when the corresponding brake line is going to be connected.
- Installation is in reverse order of removal.
To bleed the brake system, it is first necessary to activate the hydraulic pump for traction control V156 .
- Perform the activation of the hydraulic pump for traction control in the base setting display group number 2. Perform base setting in Vehicle diagnostic, test and information system in Guided Fault Finding.
Page 30 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
For this, use the Go to button in the "Functions/Component selection" .
- Bleed brake system 47-4, Braking system, bleeding .
- Enter radio code.
- Code control module Coding the control module with the Vehicle diagnostic, test and information system in Guided Fault Finding.
Tightening torques: Brake lines to ABS assembly and hydraulic pump for traction control: Thread M 10 x 1 14 NmThread M 12 x 1 14 Nm
Nut for ABS hydraulic unit N55 to bracket Item - 14 - .
Nut for Hydraulic pump for traction control V156 to bracket Item - 14 - .
Bracket hex bolt to body Item - 10 - .
ABS/EDL/ASR/ESP Bosch 5.3, assembly overview, from model year 2000 - Vehicles from VIN 3B Y 000 001
Page 31 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Tandem brake booster
On gasoline engines the vacuum required is taken from the intake manifold.
As of model year 2001, vehicles with a gasoline engine and automatic transmission are equipped with a brake vacuum pump
47-6, Brake system vacuum pump V192 .
To produce vacuum with diesel engines, a vacuum pump is equipped.
Functional check:
- With engine switched off, depress brake pedal firmly several times (to exhaust
Page 32 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Removing and installing 47-8, Brake booster, removing and installing (vehicles as of model year 2000)
Brake line connection
To left rear brake caliper
Marked on hydraulic unit with "HL"
Brake line connection
To right rear brake caliper
Marked on hydraulic unit with "HR"
Brake line
Brake master cylinder/secondary piston circuit to hydraulic unit
Marked on hydraulic unit with "HZ2"
Brake line
Hydraulic unit to hydraulic pump for traction control
Marked on hydraulic unit with "VLP"
Identification on the
the vacuum in the unit).
- Depress brake pedal with average foot pressure, hold and start engine. If the booster unit is working properly, the pedal will be felt to give slightly under foot (booster assist becomes effective).
- If faulty, replace completely.
Page 33 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
hydraulic pump for traction control "HE"
Brake line
To left front brake caliper
Marked on hydraulic unit with "VL"
Hex nut, 12 Nm
Threaded stud
Rubber bushing
ABS hydraulic unit
Brake line
To right front brake caliper
Marked on hydraulic unit with "VR"
Bracket
Hex head bolt, 9 Nm
Rubber bushing
Hydraulic pump for traction control
Brake line
Brake master cylinder/primary piston circuit to hydraulic pump for traction control
Identification on the hydraulic pump for traction control "HZ"
Hex nut, 9 Nm
Rubber bushing
Connection for traction control hydraulic pump
Connection for brake fluid from
Page 34 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
brake fluid reservoir
Identification on the hydraulic pump for traction control "BA"
Brake pressure sensor
Always replace together with the hydraulic pump for traction control.
Bracket
Application Parts Catalog
Rubber bushing
Hex head bolt
Tandem master cylinder
Cannot be repaired. If faulty, replace completely.
Removing and installing 47-7, Brake master cylinder, removing and installing (Vehicles as of model year 2000)
T 45 torx socket head bolt, 25 Nm
Self-locking nut, 49 Nm
Sealing plug
Moisten with brake fluid and press into brake fluid reservoir
Brake fluid reservoir
Seal ring
Cap
Vacuum hose
Insert into brake booster unit
Page 35 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Seal ring
Connection of brake lines from tandem master cylinder and the hydraulic pump for traction control to the hydraulic unit for ABS/EDL/ASR and ESP
A - Hydraulic unit to hydraulic pump for traction control
- Marked on hydraulic unit with VLP ,
- Identification on the hydraulic pump for traction control HE
B - Hydraulic unit to master cylinder secondary piston circuit
- Marked on hydraulic unit with HZ2
1 - Hydraulic unit to left front brake caliper
- Marked on hydraulic unit with VL
2 - Hydraulic unit to right front brake caliper
- Marked on hydraulic unit with VR
3 - Hydraulic unit to right rear brake caliper
- Marked on hydraulic unit with HR
4 - Hydraulic unit to left rear brake caliper
- Marked on hydraulic unit with HL
ABS Hydraulic Unit N55 with Hydraulic pump for traction control V156 , removing and installing
Special tools, testers and auxiliary items required
Page 36 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Torque wrench V.A.G 1331
Brake pedal loading device V.A.G 1869/2
The ABS hydraulic unit N55 and hydraulic pump for traction control V156 are located in the left side of engine compartment.
Page 37 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
1 - Hydraulic unit with ABS return flow pump
The hydraulic unit and ABS return flow pump form one unit and must always be replaced together if malfunction exists.
2 - Hydraulic pump for traction control with brake pressure sensor.
The hydraulic pump for traction control and the brake pressure sensor form one unit and must always be replaced together if malfunction exists.
Warning!
Do not bend the brake lines in the area of the hydraulic unit!
Removing
- Note or request radio code on vehicles with coded radio if necessary.
- Disconnect battery.
- Release hydraulic unit connector - arrow 1 - and pull off - arrow 2 - .
- Install brake pedal loading device V.A.G 1869/2 .
- Depress brake pedal with brake pedal loading device V.A.G 1869/2 .
- Connect bleeder bottle hose to left front brake caliper bleeder screw and open bleeder screw.
- Close left front bleeder screw.
- Place sufficient lint-free cloths under hydraulic unit.
Make sure no brake fluid gets onto contacts.
These procedures are only for removing the hydraulic unit.
Page 38 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Detach brake lines from the hydraulic unit.
- Plug brake lines and threaded holes with sealing plugs from repair kit Part No. 1H0 698 311 A.
- Remove hex nuts on bracket for hydraulic unit - arrows - .
- Remove hydraulic unit with control module.
These procedures are for removing the ABS hydraulic unit N55 and the hydraulic pump for traction control V156
- Remove power steering fluid reservoir - 1 - and set aside with hoses connected.
- Remove coolant reservoir - 2 - and set aside with coolant hoses connected.
Vehicles with electrical vacuum pump
- Remove electrical vacuum pump 47-6, Brake system vacuum pump V192 , removing and installing .
Continued for all vehicles
- Remove brake lines to the hydraulic unit and hydraulic pump for traction control.
Page 39 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Plug brake lines and threaded holes with sealing plugs from repair kit Part No. 1H0 698 311 A.
- Disconnect connector from hydraulic pump for traction control.
- Pull off brake fluid supply hose from the hydraulic pump for traction control.
- Unfasten bolts on bracket for hydraulic unit.
- Remove the hydraulic unit with hydraulic pump for traction control upward.
Installing
Remove sealing plugs on new hydraulic unit when the corresponding brake line is going to be installed.
- Further installation is in the reverse sequence of removal.
To bleed the brake system, it is first necessary to activate the hydraulic pump for traction control V156 .
- Perform the activation of the hydraulic pump for traction control in the base setting display group number 2 Perform base setting in "Guided Fault Finding" with Vehicle diagnostic, test and information system VAS 5051 .
For this, use the Sprung button in the "Functions/Component selection" .
- Bleed brake system 47-4, Braking system, bleeding .
- Enter radio code.
- Perform control module coding Coding the control module with the Vehicle diagnostic, test and information system in . Guided Fault Finding
Tightening torques: Brake lines to ABS assembly and hydraulic pump for traction control: Thread M 10 x 1 14 NmThread M 12 x 1 14 Nm
Nut for ABS hydraulic unit N55 to bracket Item - 7 - .
Nut for Hydraulic pump for traction control V156 to bracket Item - 17 - .
Bracket hex bolt to body Item - 13 - .
Page 40 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
ABS/EDL/ASR/ESP Bosch 5.7, assembly overview, as of model year 2002
Tandem brake booster
On gasoline engines the vacuum required is taken from the intake manifold.
Vehicles with a gasoline engine and automatic transmission are equipped with a vacuum pump for brakes 47-6, Brake system vacuum pump V192
To produce vacuum with diesel engines, a vacuum pump is equipped.
Functional check:
- With engine switched off,
Page 41 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
With adhesive seal
Removing and installing 47-9, Brake master cylinder with brake booster
Brake line
Brake master cylinder/primary piston circuit to hydraulic unit
Marked on hydraulic unit with "HZ1"
Brake line
Brake master cylinder/secondary piston circuit to hydraulic unit
Marked on hydraulic unit with "HZ2"
Brake line
To left front brake caliper
Marked on hydraulic unit with "VL"
Brake line
To right front brake caliper
Marked on hydraulic unit
depress brake pedal firmly several times (to exhaust the vacuum in the unit).
- Depress brake pedal with average foot pressure, hold and start engine. If the booster unit is working properly, the pedal will be felt to give slightly under foot (booster assist becomes effective).
- If faulty, replace completely.
Page 42 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
with "VR"
Brake line
To right rear brake caliper
Marked on hydraulic unit with "HR"
Brake line
To left rear brake caliper
Marked on hydraulic unit with "HL"
Brake Pressure Sensor 1 G201
Removing and installing 45-5, Brake Pressure Sensor 1 G201 , removing and installing
ABS hydraulic unit
ABS control module
Locking clip
Buffer
Bracket
Application Parts Catalog
Hex head bolt, 9 Nm
Seal ring
Tandem master cylinder
Cannot be repaired. If faulty, replace completely.
Removing and installing together with brake booster
47-9, Brake master cylinder with brake booster
Self-locking hex nut, 49 Nm
Page 43 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
T45 torx socket head bolt, 25 Nm
Brake fluid reservoir
Cap
Sealing plug
Moisten with brake fluid and press into brake fluid reservoir
Dowel bolt, 10 Nm
Vacuum hose
Insert into brake booster unit
Connecting brake lines from tandem master cylinder to hydraulic unit
A - Hydraulic unit to master cylinder primary piston circuit
- Marked on hydraulic unit with HZ1
B - Hydraulic unit to master cylinder secondary piston circuit
- Marked on hydraulic unit with HZ2
1 - Hydraulic unit to left front brake caliper
- Marked on hydraulic unit with VL
2 - Hydraulic unit to right front brake caliper
- Marked on hydraulic unit with VR
3 - Hydraulic unit to right rear brake caliper
Page 44 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Marked on hydraulic unit with HR
4 - Hydraulic unit to left rear brake caliper
- Marked on hydraulic unit with HL
ABS Control Module J104 and ABS Hydraulic Unit N55 , removing and installing
Special tools, testers and auxiliary items required
Torque wrench V.A.G 1331
Brake pedal loading device V.A.G 1869/2
If the hydraulic unit is faulty the whole assembly must be replaced. If the control module is faulty it can be replaced separately from the hydraulic unit.
Location:
The control module is bolted to the hydraulic unit and is located in the engine compartment on the left side.
Warning!
Do not bend the brake lines in the area of the hydraulic unit!
Removing
Page 45 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Note or request radio code on vehicles with coded radio if necessary.
- Disconnect battery.
Note:
The hydraulic control unit - 1 - for the W8 is rotated 180 .
- Remove coolant expansion tank - 2 - and set aside with coolant hoses connected.
- Release and remove connector from control module in the direction of - arrow - .
- Disconnect connector from brake pressure sensor.
- Install brake pedal loading device V.A.G 1869/2 .
- Depress brake pedal with brake pedal loading device V.A.G 1869/2 .
- Connect bleeder bottle hose to left front brake caliper bleeder screw and open bleeder screw.
- Close left front bleeder screw.
- Place lint-free cloths under the control module and
Page 46 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
hydraulic unit.
Make sure no brake fluid gets onto contacts.
- Disconnect brake lines from the hydraulic unit.
- Plug brake lines and threaded holes with sealing plugs from the repair kit Part No. 1H0 698 311 A.
- Release locking clips - 1 - from below and remove in direction of - arrow - .
- Remove hydraulic unit with control module.
Installing
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.
- Installation is in reverse order of removal.
- Bleeding brake system 47-4, Braking system, bleeding .
- Enter radio code.
- Perform control module coding Coding the control module with the Vehicle diagnostic, test and information system in . Guided Fault Finding
Tightening torques: Brake lines to ABS module: Thread M 12 x 1, SW11 14 NmThread M 12 x 1, SW12 24 Nm
Page 47 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
Brake Pressure Sensor 1 G201 , removing and installing
The Brake Pressure Sensor 1 G201 is located on the hydraulic control unit - 1 - .
Note:
The hydraulic control unit - 1 - for the W8 is rotated 180 .
Removing
This work procedure does not apply to the W8:
- Unfasten coolant expansion tank - 2 - and set aside with coolant hoses connected.
This work procedure applies only to the W8:
- Unfasten power steering fluid reservoir - 3 - and set aside with hoses connected.
Continued for all vehicles
Page 48 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview
- Disconnect connector - 1 - from brake pressure sensor - 2 - .
- Place lint-free cloths under control module and hydraulic unit.
- Remove brake pressure sensor.
Installing
- Installation is in reverse order of removal.
Tightening torque: Brake Pressure Sensor 1 G201 20 Nm
- Bleed brake system 47-4, Braking system, bleeding .
Page 49 / 49Hydraulic unit, brake booster/brake master cylinder, assembly overview