2001 BMW 525i electronic

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300-5
Suspension, Steering and Brakes - ~enerall
The E39 rear suspension subframe is used as a rigid mount-
ing platform
forthe differential (also called final drive) and rear
suspension components. The differential is mounted to the
subframe and the subframe is bolted to the body through rub-
ber bushings which help isolate drivetrain noise and vibration.
The
€39 rear suspension is known as a modified multi-link
system. Three control arms on each side locate the rear
wheels.
The lowercontrol arm, called the swing arm, is attached to the
wheel bearing carrier through a pivoting integral link.
An eccentric mounting bolt at the rear inner mounting of the
swing arm is used for rear camber adjustment.
The inner end of the upper front control arm, called the trac-
tion strut, is also mounted with an eccentric fastener, used to
adjust rear toe.
Drive axles with constant-velocity (CV) joints at both ends
transfer power
from the differential to the road wheels.
Sedan models
The rear suspension in sedan models uses coil springs over
strut shock absorbers. The bottom of each strut bolts to the
wheel
carrier.The top strut mount attaches just below the rear
parcel shelf of the car.
Sedan models fitted with EDC (Electronic Dampening Con-
trol) use air struts.

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300-6
/Suspension, Steering and Brakes - General
Rear suspension sedan models
Coil spring
Strut
-
'01 arm
Sport Wagon models
In order to provide a wide, ilat iloor in the cargo compartment,
the rear suspension on the Sport Wagon is unique to itself.
The shoclcabsorber is attached diagonally between the lower
swing arm and a mounting bracket on the subframe. The
spring on each side is mounted between a perch at the top
oi
the wheel bearing carrier and the bottom of the cargo com-
partment floor.
Starting with
1999 Sporl Wagon models, a self-leveling air
suspension system with electronic height control (EHC) was introduced. The system is standard on
V-8 models and op-
tional on 6-cylinder models.
On models fitted with electronic height control (EHC) rear
suspension, the standard coil springs are replaced by air
springs. Air pressure in the air springs is automatically con-
trolled by the
EHC system to compensate for ride height and
load variations.

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Suspension, Steering and Brakes - General
WHEELS AND TIRES
Tire size is critical to the properoperation of the antilock brake
system and traction control system. Several differentstyles of
wheels in
15,16, and 17 inch diameters are available from an
authorized BMW dealer.
Rim and tire size applications are listed in the table below.
Rim and tire sizes table
ELECTRONIC BRAKE AND STABILITY
CONTROL SYSTEMS
Model
5251
5281
530i
540i (manual
transmission)
540i (automatic
transmission)
All
E39 vehicles are equipped with the Antilock Braking Sys-
tem
(ABS). Early production models featured ABS with Auto-
matic Stability
control (ABSIASC). Later models came
equipped with ABS and Dynamic Stability Control
(ABSIDSC). DSC builds upon the existing ABSIASC system
to provide electronic control of drive and braking systems to
insure vehicle stability.
This manual will refer to these systems as ABS. ASC or DSC
will be specified when necessary. ABS component replace-
ment is covered in
340 Brakes.
Standard
ABS applications are shown in the accompanying table
Rim size
16x7
15x7
16x7
17x8
16x7 Optional
Tire size
225160R-15
235145-1 7
225155-1 6
Rim size
17x8
Front 17
x 8 Rear 17 x 9
17 x 8
Front 17x8
Rear 17x9
Front 17 x 8
Rear 17 x 9 Tire
size
245145R-17
Front 235145-1 7
255140R-17
235145R-17
Front 235145-1 7
Rear
255140R-17
Front 235145-17
Rear 255140R-17

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300-1 2
I Sus~ension, Steerincl and Brakes - General
E39 electronic brake and stability control
systems application table
(528i, 54bi) Traction (ASC) I Hydraulic unit in right rear of engine compartment 1
Identifiers
Year (model)
I No precharge pump 1
Manuf. up to 911998 l~utomatic Stability Control plus I Electronic control module next to glove compartment
System
Precharge pump in
lefl front of engine compartment, below
steering fluid reservoir
Separate rotational rate (yaw) and lateral acceleration sensors
I I
Combined rotational rate (yaw) and lateral acceleration sensors
Electronic control
module next to glove compartment
Hydraulic unit in right rear of engine compartment
Manuf. up to 911999
(540i optional)
I I
ABS system
Dynamic Stability Control (Bosch
DSC
Ill v. 5.3)
The electronically controlled
ABS maintains vehicle stability
and control during emergency braking by preventing wheel
lock-up.
ABS provides optimum deceleration and stability dur-
ing adverse conditions. It automatically adjusts brake system
hydraulic pressure at each wheel to prevent wheel lock-up.
Control
moduleihydraulic unit
in right rear of engine compartment
No precharge pump
Manuf. from
911999
(all models)
Automatic Stability Control (ASC)
Dynamic Stability Control (Boscli
DSC Ill v. 5.7)
NOJE-
ASC (Automatic Stability Control) may also be referred to as
ASCiT (Automatic Stability ControkTraction).
ASC works in conjunction with ABS and the engine manage-
ment system to enhance vehicle control. The main function of
the
ASC system is to maintain the contact between the tires
and the road surface under all driving conditions. This is
achieved through exact application and management of brak-
ing and drivetrain forces.
The
ASC system improves traction by electronically applying
the rear brakes when the rear drive wheels are spinning at a
faster rate than the front wheels. The combined
ABSIASC
control module, operating through the ABS hydraulic control
unit, modulates braking force at the rear wheels.
In addition,
ASC overrides the throttle opening to reduce en-
gine torque and maintain vehicle traction. Because the throt-
tle is controlled electronically, the driver cannot increase
engine power output during
ASC intervention regardless of
how far the accelerator pedal is pushed.

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Front ~us~ensionl
Spread steering knuckle slot in
tool
31 2 200.
pinch collarwith BMW special
4 Worlting in engine compartment at strut tower:
- If applicable, disconnect plug connector at top of strut for
Electronic Damper Control and remove cap from cable.
Remove upper strut bearing mounting fasteners
(arrows).
WARNING-
Do not remove centerstrut retaining nut.
4 Use lever to push down on wheel hub. Tilt strut outward
NOTE-
Use masking tape to protect fender arch from possible dam-
age.

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330 Rear Suspension
General . . . . . . . . . . . . . . . . . . . . . . . . . . . ,330-2
Special tools . . . . . . . . . . . . . . . . . . . . . . . . ,330-2
Rear suspension variations . . . . . . . . . . . . ,330-4
Rear Struts and Springs
(sedan models)
. . . . . . . . . . . . . . . . . . . . ,330-5
Rear strut assembly, removing
and installing
. . . . . . . . . . . . . . . . . . . . . . . ,330-5
Rear strut assembly, disassembling
and assembling
. . . . . . . . . . . . . . . . . . . . . ,330-7
Rear Shock Absorbers and
Springs (Sport Wagon models)
. . . . . ,330-9
Rear shock absorber, removing
and installing
. . . . . . . . . . . . . . . . . . . . . . . ,330-9
Coil spring, removing and installing . . . . . ,330-1 1
Air spring, removing and installing
. . . . . . ,330-12
Rear Suspension Arms,
Subframe and Bushings . . . . . . . . . . ,330-13
Rear suspension arm components . . . . . . ,330-1 3
Swing arm, removing and installing (sedan models)
. . . . . . . . . . . . . . . . . . . . . ,330-1 4
Swing arm, removing and installing (Sport Wagon models)
. . . . . . . . . . . . . . . ,330-16
Swing arm ball joint, replacing . . . . . . . . . ,330-1 9
Upper rear control arm, removing
and installing (sedan models)
. . . . . . . . . . .330-22
Upper rear control arm, removing
and installing (Sport Wagon models)
. . . . .330-23
Upper front control arm (traction strut),
removing and installing
. . . . . . . . . . . . . . . ,330-25
Rear axle assembly, removing and
installing (sedan models)
. . . . . . . . . . . . . ,330-26
Rear axle assembly, removing and
installing (Sport Wagon models)
. . . . . . . ,330-28
Rear subframe mounting bushings,
removing and installing
. . . . . . . . . . . . . . . .330-31
Rear Wheel Bearings . . . . . . . . . . .
Rear wheel bearing carrier, removing
and installing (sedan models)
. . . . . . .
Rear wheel bearing carrier, removing
and installing (Sport Wagon models)
. .
Rear wheel bearing, replacing . . . . . . .
Rear Stabilizer Bar
Stabilizer bar, removing and installing .
Stabilizer bar link, removing
and installing
. . . . . . . . . . . . . . . . . . . .
Electronic Height Control (EHC)
Component Replacement
. . . . . . .
Electronic height control (EHC)
components
.....................
Air compressor pump relay, removing
and installing
. . . . . . . . . . . . . . . . . . . .
EHC control module, removing
and installing
. . . . . . . . . . . . . . . . . . . .
Air supply unit, removing and installing
Ride height sensor, removing
and installing
. . . . . . . . . . . . . . . . . . . .

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--
C. -- -- - -- Rear ~us~ensionl
Depending on year and model applications, the Sport Wagon
rear suspension may be equipped with:
Conventional shock absorbers and coil springs
Electronic height control (EHC) system which incorporates
air springs
NOTE-
. Suspension and EHC troubleshooting is covered in 300
Suspension, Steering and Brakes-General.
EHC system repairs, other than air spring replacement,
are covered in Electronic height control
(EHC) compo-
nent replacement.
Replace shock absorbers and springs in pairs only.
Rear shock absorber, removing and
installing
- Raise car and remove rear wheels,
WARNING-
Male sure that the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place
jack stands under
suspension parts.
CAUTION-
If working on a vehicle with compressedairshock absorbers,
disable air supply pump by disconnecting electrical plug be-
fore performing any repairs. Pump is located beneath a cover
under the spare tire in the floor of the cargo compartment.
- Support swing arm from below
CAUTIOG
The shock absorber prevents the drive axle and wlieel bear-
ing carrier from dropping too far. Supporting the wheel bear-
ing carrier before disconnecting the shock absorber
mounting fasteners prevents damage to the
brake hose,
parking
brake cable and drive axle CVjoints.
- Working in cargo compartment, remove carpet. Remove tri-
angular upper shock mount covers located beside spare tire
well.
- If applicable: Detach air supply line from shock absorber.
Plug ports and lines to keep out dirt.

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Rear Suspension
Air spring, removing and installing
CAUTION-
If vehicle is driven with airspring depressurized, the airspring
will be permanently damaged and must be replaced.
An air spring is made from a flexible rubber material which
forms an airtight cavity. It is pressurized by an air supply
pump activated by an electronic control unit to provide a
vari- . . able spring rate depending on vehicle load
CAUTIOIG
Disable air supply pump by disconnecting electrical plug
before performing any repairs. Pump is located beneath a
cover under the spare tire in the floor of
the cargo compart-
ment.
When removing and installing air connections, extreme
cleanliness must be followed. Small dirt particles can
cause leakage in the system.
Remove luggage compartment floor mat.
- Working above air spring, loosen quick coupling screw con-
nection to allow
air pressure to escape.
- Once pressure has been reduced, retighten screw.
Tightening torque Quick coupling screw
to air pump 2 Nm (18 in-lb)
- Remove quick coupler. Plug openings to keep dirt out,
- Remove air spring mounting clips.
- Raise car and remove rear wheels.
Make sure the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place
jaclc stands under
suspension parts.
- Working underneath rear suspension, lift wheel bearing car-
rier to relieve rear spring tension. Then unbolt air spring
mounting bolt from seat on wheel bearing carrier. Remove air
spring.
NOTE-
Left and right air springs are different. The left air spring is
marked with a red identification
marl. The right air spring is
marked with a blue identification mark.