Removing and installing ABS control unit J104 and ABS hydraulic unit N55, vehicles with TDI engine — AUDI

Removing and installing
ABS control unit
J104
and
ABS hydraulic unit
N55
, vehicles with TDI engine
Note
Chapter
“
Exploded view - control unit and hydraulic unit
”
.
When renewing
ABS control unit
J104
/
ABS hydraulic unit
N55
, select the
“Replace”
function for the
ABS control unit
J104
/
ABS hydraulic unit
N55
using
Vehicle diagnostic tester
,
Guided Functions
.
Special tools and workshop equipment required
Vehicle diagnostic tester
Torque wrench
V.A.G 1331
Brake pedal actuator
V.A.G 1869/2
Bleeder bottle from
brake filling and bleeding equipment
VAS 5234
Sealing plugs from
assembly parts set
5Q0 698 311
M10 sealing plugs
M12 sealing plugs
Removing
Insert
brake pedal actuator
V.A.G 1869/2
between brake pedal and driver's seat. Depress brake pedal by at least 60 mm.
Note
This closes the valves in the brake master cylinder and stops the brake fluid reservoir from running empty.
WARNING
Risk of skin irritation
Always wear chemical-resistant protective gloves to prevent brake fluid from contacting skin.
Detach protective cap
3
from bleeder screw
1
on front left brake caliper.
Connect hose
2
from bleeder bottle, as shown in illustration.
Open bleeder screw to relieve pressure in brake system.
Close bleeder screw and remove bleeder bottle.
Repeat procedure on rear left brake caliper.
Note
The
brake pedal actuator
V.A.G 1869/2
must not be removed.
Remove engine cover panel
Rep. gr.
10
Engine cover panel; Removing and installing engine cover panel
.
Remove front exhaust pipe
Rep. gr.
26
Exhaust pipes/silencers; Removing and installing front exhaust pipe
.
Release fastener
arrow
(if fitted), pull off cover
1
towards left and detach.
Note
Cover
1
is not fitted on all models.
Unclip wiring duct.
Press down retainer catch
arrow A
.
Release electrical connector
arrow B
.
Unplug electrical connector
1
.
Note
Make sure brake fluid does not get into connector housing of control unit. This can result in corrosion of the contacts and failure of the system.
Use compressed air to carefully clean connector housing if necessary.
To protect against escaping brake fluid, place a sufficient number of lint-free cloths in area beneath hydraulic control unit.
Caution
Risk of damage to brake lines
Do not attempt to bend to a different shape.
Mark brake lines to hydraulic control unit.
Unscrew union screws in the sequence
1 … 6
and push brake lines slightly to the side.
Seal open connections immediately using clean sealing plugs from
assembly parts set
5Q0 698 311
.
Detach hydraulic control unit
1
upwards
arrow
.
Turn hydraulic control unit in engine compartment so that mounting bracket faces upwards.
Unscrew bolts
arrows
and detach mounting bracket
1
from hydraulic control unit.
Turn hydraulic control unit and place it on subframe.
Take out hydraulic control unit from below.
Caution
Risk of irreparable damage to hydraulic control unit
Do not unscrew pump motor from hydraulic control unit.
Installing
Installation is performed in reverse sequence; note the following:
Place hydraulic control unit on subframe from below.
Attach mounting bracket for hydraulic control unit in vehicle.
Press hydraulic control unit
1
with bracket onto studs in engine compartment
arrows
.
Note
The hydraulic control unit must be seated correctly on all studs.
Do not remove sealing plugs from new hydraulic unit until corresponding brake line is ready to be fitted.
If the sealing plugs are removed from the hydraulic unit sooner, brake fluid may escape and it may no longer be possible to fill and bleed the unit properly.
When installing the hydraulic control unit, ensure that the rubber dampers are not pressed out of the bracket.
Markings on hydraulic unit:
A
Hydraulic unit to brake master cylinder (primary piston circuit), -HZ2-
B
Hydraulic unit to brake master cylinder (secondary piston circuit), -HZ1-
1
Hydraulic unit to rear right brake caliper, -HR-
2
Hydraulic unit to front left brake caliper, -VL-
3
Hydraulic unit to front right brake caliper, -VR-
4
Hydraulic unit to rear left brake caliper, -HL-
Insert all brake lines into
ABS hydraulic unit
N55
, screw in union screws by hand and tighten in the sequence
1 … 6
.
Remove
brake pedal actuator
V.A.G 1869/2
.
Chapter
“
Bleeding hydraulic system
”
.
Install front exhaust pipe
Rep. gr.
26
Exhaust pipes/silencers; Removing and installing front exhaust pipe
.
Install engine cover panel
Rep. gr.
10
Engine cover panel; Removing and installing engine cover panel
.
When renewing
ABS control unit
J104
/
ABS hydraulic unit
N55
, select the
“Replace”
function for the
ABS control unit
J104
/
ABS hydraulic unit
N55
using
Vehicle diagnostic tester
,
Guided Functions
.
WARNING
Risk of accident!
Make sure that the brakes work properly before the vehicle is driven on the road.
Tightening torques
Chapter
“
Exploded view - control unit and hydraulic unit
”