1997 BMW 528i drive

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300-8
Suspension, Steering and Brakes - General
Rear suspension Sport Wagon
(EHC with air springs)
Air sprIn9 Shock absorber I
(tiaction strut) arA
(lower control arm) Integral arm 502330210
EHC initiates a control sequence as necessary. The system
offers the following features:
Control system independent from vehicle engine (no en-
gine driven hydraulic pump system)
Individual control of rear wheels
Uneven load identified and compensated for
Uneven road surfaces identified and not compensated for
Automatic control interrupted when cornering
System diagnosable using the
BMW Service Tester (DIS-
plus, GTI, or MoDiC)

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300-1 0
/Suspension, Steering and Brakes - General
The steering system features variable power assist provided
by an engine-driven hydraulic pump.
Rack and pinion steering
6-cylinder models
(525i, 5281, 5300
Two types of steering systems are used in E39 models. 6-
cylinder (525i, 5281, 530i) models are equipped with a steer-
ing rack system. V-8
(540i) models are equipped with a re-
circulating ball and nut steering gearbox.
Rack-and-pinion steering
Steering components in 6-cylinder models consist of a rack-
and-pinion type steering gear and connecting linltage to the
road wheels.
The steering linkage connects the rack-and-pinion unit
through tie rods to the steering knucltles. The tie rod ends al-
low the wheels to pivot and react to suspension travel.
Recirculating ball and nut steering
V-8 models
(540i)
I
Recirculating ball and nut steering
Recirculating ball and nut steering in V-8 models consists of a
steering box with integrated hydraulic control valve and con-
necting linkage to the road wheels.
Thesteering linkageconnects the steering gearbox through a
pitman arm to the wheels. An idler arm maintains correct toe
angle. The tie rod allow the wheels to pivot and react to sus-
pension travel.
E39 cars are equipped with power disc brakes with integral
antilock brakes (ABS). The parking bralte is a dual-drum sys-
tem integrated with the rear brake rotors.
Power assist is provided by a vacuum booster when the en-
gine is running. The brake pedal
pushrod is connected direct-
ly to the master cylinder, so failure of the vacuum booster
does not normally result in total
bralte failure.
Each disc bralte uses a caliper with a single hydraulic cylin-
der. Brake pads in the left front and right rear contain wear
sensors. When brake pads need replacement, the sensors il-
luminate a light on the dashboard.

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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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I Steerina and Wheel Alianment
Steering
system
Two types of steering gear are used in the E39 series models.
6-cylinder
(5251, 528i and 530i) models are equipped with
rack and pinion steering. The steering rack is mounted to
an aluminum subframe.
V-8
(540i) models are equipped with a recirculating ball
and nut steering gearbox mounted to a steel subframe.
At low speeds, maximum power assist is provided to ease
parking and city driving. At high speeds, assist is reduced to
ensure stability. The power steering system varies assist
based on engine speed.
Power boost for the steering is provided by an engine-driven
hydraulic pump. A hydraulic control valve is used to control
boost pressure.
The steering wheel connects to the steering gear via an ad-
justable steering column which incorporates a rubber cou-
pling ("guibo") to dampen vibration and noise.
Power steering fluid is supplied from the fluid
reservoir to the
pump and to the steering gear via rubberlmetal hoses.
The return line from the steering gear to the
reservoir loops
into the airstream in front of the radiator and connects to the
steering fluid cooler. The fluid cooler is attached to a cassette
which also includes cooling coils for engine oil, transmission
fluid and AIC condenser.
The steering gear requires no maintenance other than align-
ment and periodic inspection for worn components. Inspect
rubber rack boots
(rack and pinion system) and tie-rod end
boots periodically for tears or damage. Replace
if necessary.
-
NOTE-
The airbag system is traditionally referred to as Supplemen-
tal Restraint System (SRS). The
BMW versfon of SRS used
m the E39 models is known as the Multiple Restraint System - (MRS). - -

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320-8
Steering and Wheel Alignment
4 MFL steering wheel: Loosen 2 airbag mounting fasteners
(Torx T27 or T30) located at rear of steering wheel (arrow).
4 Sport steering wheel:
Insert screwdriver through opening in rear of steering
wheel and push against spring tension to release
airbag.
Repeat procedure on other side of steering wheel.
- Carefully lift airbag from steering wheel and disconnect elec-
trical harnesses from
back side of unit. Refer to component
illustrations above. Also see
721 Airbag System (SRS).
Improper handling of the airbag could cause serious injury.
Store the
airbag with the horn pad facing up. If stored facing
down, accidental deployment couldpropel it violently into the
Avoid damaging the variety of convenience switches, such
as radio and cruise controls, installed in the steering wheel of
4 Remove steering wheel center bolt (arrow).

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320-1 0
Steering and Wheel Alignment
Steering column
components
1. Steering lock
2. Lower steering shafl
3. Horizontal drive motor
4. Longitudinal adjusting drive
shafl
5. Steering column support
6. Vertical adjusting drive shafl
7. Vertical drive motor
8. Lower support ring for steering
angle sensor
9. Upper support ring for steering
angle sensor
10. Steering angle sensor
11. Upper steering shafl
12. Steering shafl bearing
13. Bearing inner sleeve
14. Circlip
15. Collar
16. Steering wheel mounting bolt
Steering column trim, removing and
replacing
- Tilt steering column down and extend fully.
- Remove plastic retaining screw from upper trim cover,
4 Push in sides of upper trim cover (arrow) to release from
lower trim. Pull back and up on upper trim.

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Steering and Wheel Alignment
Power assist is provided by a belt-driven pump at the lower
left front of the engine. The power steering fluid reservoir is lo-
cated at the left side of the engine compartment.
Power steering pump, removing and
installing
When working with power steering components, absolute
cleanliness is needed to ensure proper operation of the hy-
- Empty power steering fluid reservoir using clean syringe. Do
not reuse fluid.
- Raise front of car. Remove splash shield from under engine.
WARNING-
Make sure 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
Darts.
Remove drive belt from power steering pump. See
020 Main-
tenance.
Remove alternator cooling duct
Remove fluid hoses from pump. Plug openings in pump and
hose ends.
Remove pump front mounting bolts
(A).
Remove fluid line support bracket (B)
Remove pump rear mounting bolt (arrow)
- Installation is reverse of removal, noting the following:
Make sure all thread bores, bolts, nuts, fluid couplings and
mating
surfaces are clean, and inside surface of multi-
ribbed-belt is free of grease and dirt.
Use new sealing washers when reattaching power steer-
ing pressure lines.
Make sure hoses have adequate clearance from chassis.
Install front pump fasteners.