Front BMW 525i 2001 E39 Workshop Manual

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340-8
1 Brakes
Brake bleeding is usually done for one of two reasons: either
to replace old brake fluid as part of routine maintenance or to
expel trapped air in the system that resulted
from opening the
brake hydraulic system during repairs.
Read the
Warnings listed below before beginning the bleed-
ing procedure an on any
E39 car. If air enters the ACS or DSC
hydraulic unit, the factory BMW Service Tester MUST be
used in conjunction with a bralte pressure bleeder before the
vehicle is driven.
The BMW
ServiceTester (DISpluslGT1iMoDiC) must be
used to bleed the braltes if:
Any hydraulic brake system components are replaced, in-
cluding bralte lines.
Air has enter the
ABSIASC or ABSlDSC hydraulic unit.
WARNING -
* The ASC and DSC systems use electronic controls and a
sophisticated hydraulic unit Once air enters the hydraulic
unit, it is very difficult to remove using traditional methods.
For this reason, pressure
brake bleeding should be done
in conjunction with the BMW
Sewice Tester (DIS-
plus/GTl/MoDiC). The tester electrically cycles the hy-
draulic unit solenoids in the hydraulic unit while
pressurized brake fluid is forced through the system.
When flushing the brake fluid from the system, use ex-
treme care to not let the
brale fluid reservoir run dry If
air enters the hydraulic unit, the BMW Service Tester
MUST be used to bleed the brale system before the
vehicle is driven.
Always use new brake fluid from an unopened container. It is
important to bleed the entire system when any part of the hy-
draulic system has been opened. Be sure to have the special
equipment needed before beginning the job.
When bleeding the
braltes, start atthe wheel farthest from the
master cylinder and progress in the following order:
right rear brake
left rear brake
* right front brake
left front brake

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Brakes
- Open bleeder screw. Carry out bleeding procedure with
BMW Service Tester until clear, bubble-free fluid flows.
Models with DSC: After BMW Service Tester bleeding rou-
tine has finished, press brake pedal to floor
5 times until
clear, bubble-free fluid runs out. Close right rear bleeder
valve.
Models with ASC: Close right rear bleeder valve.
- Repeat procedure at left rear brakes.
- Repeat BMW Service Tester bleeding at right front brakes.
Models with DSC: After
BMW Service Tester bleeding rou-
tine has finished, press brake pedal to floor
5 times until
clear, bubble-free fluid runs out. Close right front bleeder
valve.
Models with ASC: After BMW Service Tester bleeding rou-
tine has finished, press brake pedal to floor
12 times until
clear, bubble-free fluid runs out. Close right front bleeder
valve.
- Repeat procedure at left front brakes.
- Remove brake bleeding apparatus and disconnect BMW
Service Tester. Top up brake fluid. Check to make sure
brake 1
fluid reservoir cap seal is intact.
Tightening torques Bleeder screws (wrench size)
- 7 rnrn screw
3.5 - 5 Nrn (2.5 - 3.7 ft-lb)
11 rnrn screw 12-16Nrn(9-12ft-lb)

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Brakes
BRAKE PADS, CALIPERS AND ROTORS
Brake pads,
calipers, and rotors
Braking system
components
1. Brake caliper guide bolts
2. Brake caliper
3. Brake pad wear sensor
4. Brake pad anti-rattle clip
5. Brake pads
6. Front brake rotor retaining bolts
7. Front brake rotor
8. Rear brake rotor retaining bolt
9. Rear brake rotor
10. Parking brake shoes with hard-
ware
11. Rear brake backing plate
12. Brake pad carrier
13. Brake pad carrier retaining bolts

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340-1 2
Brakes Brake pads, checking and replacing
Brake pads can be replaced without disconnecting the brake
fluid hose from the caliper or having to bleed the brakes. The
rotors can be replaced without disassembling wheel hub and
bearing. Always machine or replace rotors in pairs. Replace
pads in sets.
Front and rear brake pad replacement procedures are identical.
WARNING -
* Altllough semi-metallic andmetallic brale friction materials
in brake pads or shoes no longer contain asbestos, they
produce dangerous dust.
Treat all
brale dust as a hazardous material.
Do not create dust by grinding, sanding, or cleaning
brake friction surfaces with compressed air.
CAUTION--
Pressing caliper piston in may cause brake fluid reservoir to
overflow To prevent this, use a clean syringe to first remove
some fluid
from reservoir.
Raise car and remove wheels,
WARNING-
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
parts.
/ 4 To measure brake pad lining thickness, insert BMW special
n 1 tool 34 1 260 at either frontilght wheel or left rear wheel -
Move wheel until notch for brake wear indicator can be
seen through wheel opening.
Insert tip of tool into notch so that the body of tool rests on
brake pad backing plate
(A), and tip touches bralte disc
(B).
Replace pads if thickness is 3.0 mm (0.12 in) or less.
Pry off
bralte calipe~ , anti-rattle spring (arrow).

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340-1 4
Brakes
4 Apply a thin coating of BMW anti-squeal compound to caliper
contact face
(arrow).
Do not apply grease to brake pad backing plate.
Right Left
CAUTION-
Do not let calliper rubber dust sleeve come in contact with
anti-squeal compound. The rubber will swell and deteriorate.
4 Apply a thin coating of BMW anti-squeal compound to bralte
pad rests (arrows) on pad carrier.
4 When installing directional brake pads, install the marked
pads as shown.
NOTE-
BMW-supplied (OEM) front brake pads may be marked as di-
rectionalpads. Aftermarket brands are generally not labeled
as directional. When installing directional pads, be sure to in-
stall them as indicated in the illustration.
- Where applicable, insert brake pad wear sensor into cutout
in new pad. Push sensor into pad cutout until it locks into
place.
- -
- NOTE-
If brake lining indicator light illuminatedprior to brake pad re-
placement, replace wear sensor.
- Route pad wear sensor wiring through caliper opening and
under bleeder dust cap.

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340-1 5
Brakes
- Remainder of installation is reverse of removal.
- Clean brake caliper mounting bolts (7 mm Allen). Replace
ones which are not in perfect condition. Do not grease.
Top up brake fluid to MAX marking.
- Before driving car, pump bralte pedal several times so that
brake pads contact brake rotors.
Check that brake fluid level is correct. Top up if necessary.
Hold ignition key for at least
30 seconds in accessory po-
sition without starting engine. This clears any fault codes in
memory and turns off brake pad warning light.
Tightening torques Brake caliper to pad carrier
(7 mm Allen)
Front caliper
30 Nm (22 It-lb)
- Rear caliper 28 Nm (21 It-lb)
Road wheel to hub
120i 10 Nm (89i7 ft-lb)
Brake rotors, removing and installing
- Raise car and remove wheels
WARNING-
Male 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
parts.
Remove brake caliper carrier bolts (arrows). Suspend brake
caliper from chassis using stiff wire.
NOTE-
Hydraulic brake line remains connected.
4 Remove bralte rotor mounting screw (arrow) and remove ro-
tor.
- Inspect rotor for cracks, signs of overheating and scoring.
- Minimum allowable thickness (MIN TH) is stamped on rotor
hub. Measure rotor braking surface with a micrometer at
eight to ten different points and use the smallest measure-
ment. Compare to specifications in table below.
- If rotor does not pass minimum thickness requirements or is
damaged, replace rotor.

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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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1 Brakes
Pull down panel
If applicable, disconnect electrical harness
rows) from 16-pin OBD-ll plug.
Remove panel from interior. connectors
(ar-
Working
above and in front of pedals, remove locking clip (A)
and slide brake booster pushrod off bralte pedal pin. Remove
brake booster mounting nuts
(6).
Working in engine compartment, carefully separate bralte
booster from engine compartment bulkhead.
CAUTION-
Do not use force on booster when separating from bulkhead.
This can damage booster and pushrod.
Remove booster by tilting out in direction of engine. Lift
booster up and out of engine compartment.
- Installation is reverse of removal, noting the following:
Make sure all nuts, fluid couplings, thread bores and mat-
ing surfaces are clean.
Replace bralte booster self-locking mounting nuts.
Replace sealing O-ring between master cylinder and bralte
booster.
Bleed bralte system as described earlier.
CAUTION--
Do not over-torque tlie master cylinder mounting bolts.
This could damage the
bralce booster and prevent proper
vacuum build-up.
After
30 minutes of use recheclc the torque on bralce
booster mounting nuts.
Tightening torques
Brake master cylinder to brake booster
26 Nm (19 it-lb)
Brake booster to bulkhead 22 Nm (16 it-lb)
(Recheck torque after
30 minutes of use.)
Brake fluid line to master cylinder 18 Nm (13 it-lb)
NOTE-
When replacing the brake booster check valve or vacuum
hose, install the valve so that the molded arrow is pointing to-
ward the
fntalce manifold. Use new hose clamps

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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.