1997 BMW 525i ABS

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1 Brakes
Max. machine limit per
friction ring side 0.8 mm (0.03
in) I
Brake rotor reconditioning specifications
Model
Replace
braite rotors in pairs
Bralre rotor sizes
Clean rotor with brake cleaner before installing.
Front
Model
6-cylinder
models (5251,
5281, 530i)
V-8 models (540i)
* When installing new rear brake rotors, adjust pariting brake
as described later, in Parking brake, adjusting. Rear
Vented rotor wear limit (min. thickness)
Tightening torques
Braite rotor to hub 16 Nm (12 ft-lb)
6-cylinder models
(525i, 5281, 530i)
- V-8 models (540i)
Front
296 mm (1 1.65 in)
324 mm (12.76 in)
Front bralte pad
carrler to steering ltnucitle 110 Nm (81 ft-lb)
Rear
298 mm (1 1.73 in)
Rear
brake pad carrier to wheel bearing carrier 65 Nm (48 ft-lb)
20.4
mm (0.80 in)
28.4 mm (1.12 in)
Road wheel to hub
120ilONm
(89 -t 7 it-lb)
18.4 mm (0.72 in)
The brake master cylinder is mounted to the front of the vacu-
um booster on the driverside bullthead.
-
CAUTION-
All E39 vehicles soldin the USA are equipped with Antilock
Braling System (ABS) and either Automatic Stability Control
(ASC) or Dynamic Stability Control (DSC).
In order for the
braling and stability controls to work properk if the brake
master cylinder is replaced, make sure that the brake system
is bled
by an authorized BMW dealer or other qualified repair
facility
using the BMW Service Tester. See Brake Bleeding
earlier
in this group.

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Brakes
- Pump brake pedal a few times to reduce vacuum in brake
booster. This makes removal of
check valve easier.
- Remove or loosen hose clamp(s) at check valve.
- Disconnect hoses. Remove valve to test or replace.
NOTE-
If valve is pressed into grommet in vacuum booster, pry it out
carefully.
- Reinstall valve using new hose clamps
NOTE-
Install the valve so that the molded arrow is pointing toward
the intake manifold.
Brake booster, removing and installing
CAUTIO&
All E39 vehicles sold in the USA are equipped with Antiloclc
Braking System (ABS) and either Automatic Stability Control
(ASC) or Dynamic Stability Control (DSC). In order for the
bralchg and stability controls to work properk if brake fluid
lines are disconnected and reconnected,
male sure that the
brake system is bled by an authorized BMW dealer or other
qualified repair facility using the BMW Service Tester: See
Brake Bleeding earlier in this group.
- Disconnect negative (-) cable from battery.
I CAUTION- I
Prior to disconnecting the battery read the battery discon-
nection cautions given in
001 General Cautions and
I Warnings. I
- Remove bralte master cylinder as described earlier.
- Disconnect engine vacuum hose from bralte booster.

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1 Brakes
ABS COMPONENT REPLACEMENT
CA UTIOW-
If the tires on the car are of different makes, the ABS/trac-
tion controlsystem may overreact. Only fit tires of the same
make and treadpattern.
In adverse conditions, such as trying to rock the car out
of deep snow or other soft surface, or when snow
chains are fitted, it is advisable to switch off traction
control and allow
tlie car driveline to operate conven-
tionally.
All E39 vehicles are equipped with
Antilock Braking System
(ABS). Early production models featured ABS with Automatic
Stability Control (ABS
I ASC). Later models came equipped
with ABS and Dynamic Stability Control (ABS
/ DSC). This
manual will refer to these systems as ABS. ASC or DSC will
be specified when necessary.
For ABS system and component descriptions, see
300 Sus-
pension, Steering and Brakes-General.
Wheel speed sensor, replacing
- Raise applicable end of car.
Make sure that the car is firmly supported on
jack stands de-
signed for the purpose. Place
jack stands beneath structural
chassis points. Do not place jack stands under suspension
< Front sensor: Unscrew mounting bolts (arrows) at steering
knuckle.
4 Rear sensor: Unscrew mounting bolt (arrows) in rear wheel
bearing carrier.
NOTE-
ABS wheelspeed sensor application may vary depending on
traction control system installed.

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4 Disconnect and remove speed sensor electrical harness (ar-
row) from retaining mounts. (Lefl front wheel shown).
- During installation, apply thin coat of StaburagsBNBU 12/K
or equivalent grease to speed sensor and housing.
- Installation is reverse of removal.
Tightening torque
ABS wheel speed sensor to steering knuckle or 8 Nm (6 It-lb)
rear wheel bearing carrier
ABS impulse wheel
The front and rear impulse wheels are integral with the inner
wheel bearing seal and not available as separate part. See
310 Front Suspension or 330 Rear Suspension for wheel
bearing replacement procedures.
DSC lateral acceleration or rotational rate
(yaw) sensor, replacing
DSC system on 1998 cars (Bosch DSC Ill v. 5.3): Lateral ac-
celeration sensor and rotational rate (yaw) sensor are sepa-
rate units, both mounted underneath or in front of driver's
seat.
DSC system on 1999 and later cars (Bosch DSC
Ill v. 5.7):
Lateral acceleration sensor and rotational rate (yaw) sensor
are combined into one unit, located under driver's seat.
- Remove driver's seat. See 520 Seats.
- Lateral acceleration sensor (1 998 models): Remove lower
lefl door pillar trim (driver's
kick panel) to access sensor. Pull
up carpet as necessary to reach sensor harness connector
or fasteners.
4 Rotational rate (yaw) sensor (1998 models): Remove plastic
trim at door sill to access sensor (arrow). Pull up carpet and
move insulation forward as necessary to reach sensor har-
ness connector or fasteners.
- Combined lateral acceleration / rotational rate (yaw) sensor
(1 999 and later models): Remove plastic trim at door sill to
access sensor. Pull up carpet and move insulation forward as
necessary to reach sensor harness connector or fasteners.
- Disconnect electrical harness connector at sensor.
- Combined sensor (1 999 and later models): Remove sensor
bracket mounting screws.

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Remove snap ring from steering shaft.
- Slide steering angle sensor off steering shaft
< Installation is reverse of removal, noting the following.
Take care to line up loclting pin
(arrow) with mount hole in
sensor.
Perform steering angle offset test using BMW scan tools
DISplus, GT1, or MoDiC. Once calibrated, the sensor
sends a confirmation ID code to the DSC control module
to indicate proper calibration.
DSC precharge pump, removing and
installing
(1 998 models)
1998 V-8 cars with Bosch DSC Ill v. 5.3 are equipped with a
DSC precharge pump mounted in the engine compartment.
There is no separate precharge pump in the Bosch DSC
Ill v.
5.7 system (1999 models and later).
WARNING-
E39 cars require special BMWservice equipment to properly
bleed the brakes. Removal of hydraulic components is not
recommended unless this equipment is available. For safety
reasons, the
brake system on cars with ABS must be bled us-
ing the procedures described in this repair group.
- Using a clean syringe, empty brake fluid reservoir.
CAUTIOI\C
Brake fluid is highly corrosive and dangerous to the environ-
ment. Disoose of it
orooerlv.
Working at precharge pump, disconnect hydraulic lines (A)
and electrical harness connector (6). Clean up dripping fluid.
hydraulic unit. Label all
con-

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1 Brakes
- Remove precharge pump mounting bracket fasteners and re-
move pump.
- Installation is reverse of removal, noting the following:
Be sure to replace rubber pump mounts if damaged
01
worn.
Bleed brakes as described earlier.
Tightening torque Brake line
to precharge pump 18 Nrn (13 ft-lb)
DSC pressure sensor (1 999 - 2002 models)
On 1999 and later DSC systems, the DSC pressure sensor is
screwed into the DSC hydraulic unit (right rear of engine com-
partment).
WARNING-
* €39 cars require special BMW service equipment to prop-
erly bleed the brakes. Removal of the
DSCpressure sensor
is not recommended unless this equipment is available. For
safety reasons, the brake system on cars with ABS must be
bled using the procedures described in this repair group.
Switch off ignition and remove
key to male sure brake
system cannot be activated.
- Disconnect electrical harness connector at switch.
- Use BMW special tool 34 5 160 to remove and install sensor.
Inspect threads and sealing surfaces for damage.
* Work quicltly to avoid excessive brake fluid leakage.
Tightening torque
Pressure sensor
to hydraulic 19 Nrn (14ft-lb)
unit
- Reconnect harness connector
- Bleed front brakes as described earlier.
- Press on brakes and check for leaks at sensor.
- Turn on ignition and firmly depress brake pedal. Check that
DSC warning light does not come on.

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340-31
Brakes
ABS 1 traction electronic control module
(1 997 -1 998 models)
4 The traction control electronic control module in 1997- 1998
models is located to the left of the glove compartment.
NOTE-
In both ASC and early DSC systems this location is used for
the electronic control unit.
- Before removing the traction control electronic module, read
any fault codes in memory.
ABS I DSC control module
(1 999 - 2002 models)
The DSC electronic control unit in 1999 and later models
(from 911998) is bolted to the DSC hydraulic unit in the right
rear of the engine compartment.
- Before removing the traction control electronic module, read
any fault codes in memory.
- Install electronic control unit using new screws.
Tightening torque
DSC electronic control unit to 2.9 Nrn (26 in-lb)
hydraulic
unit (use new screws)
- Code newly installed module using either DIS or MoDiC.
- Adjust steering angle sensor using menu item Service func-
tion in
DIS or MoDiC.
ABS I traction control hydraulic unit,
removing and installing
WARNING -
E39 cars require special BMWsewice equipment to properly
bleed the brakes. Removal of the hydraulic unit is not recom-
mended unless this equipment is available. For safety rea-
sons, the
brake system on cars with ABS must be bled using
the procedures described in this repair group.
NOTE-
Before starting this procedure, read control module mem-
ory and print
out diagnostic record.
DSC system: Adjust steering angle sensor using
either
DISplus, GTI, or MoDiC. After completing work, function
test control module.

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340-32
Brakes
The procedure for removing the ABS I ASC or ABS I DSC hy-
draulic unit is similar for all models. The unit is located at the
right rear of the engine compartment.
- Using a clean syringe, empty brake fluid reservoir.
CAUTION-
Brake fluid is highly corrosive and dangerous to the environ-
ment. Dispose of it
properiw
4 Disconnect electrical harness connector (A) at hydraulic unit
(1998 DSC hydraulic unit in V-8 model shown).
Where applicable, detach electrical harness connector to
DSC pressure sensor.
Mark brake lines
(arrows) in relation to their placement on
hydraulic unit. Detach lines from unit using appropriate
sized flare wrench.
Seal open brake fluid lines and bores with suitable plugs to
prevent contamination.
- Carefully push aside brake lines from retainerslgrommets
that may be in the way of hydraulic unit removal. Use care not
to
kink brake lines.
- Remove hydraulic unit mounting screws. Remove hydraulic unit.
- If necessary, separate hydraulic unit from control module.
- Installation is reverse of removal, noting the following:
Check rubber mount for hydraulic unit/control module. Re-
place if damaged.
Make sure all nuts, fluid couplings, thread bores and mat-
ing surfaces are clean.
Avoid bending pins on control module harness connector
when reattaching.
Make sure brake lines are securely seated in grommets
before installing brake lines in hydraulic unit bores.
Bleed brakes using
BMW Service Testeras described earlier.
Tightening torques Brake lines to hydraulic unit
18 Nm (13 ft-lb)
DSC electronic control unit to hydraulic unit 2.9 Nrn (26 in-lb)
(use new screws)
Hydraulic unit to body
8 Nm (6 ft-ib)
Mounting bracket to hydraulic unit 8 Nrn (6 ft-lb)