1998 BMW 540i Ac system

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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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Steering and Wheel Alignment
I Rack and r in ion steering 1 Steering system variations
I 6-~~linder'rnodels (525i,>28i, 530i) / 1. Left tie rod
2. Right tie rod
3. Steering rack
4. Steering gearbox
5. idler arm
6. Center tie rod
7. Steering knuckle
Recirculating ball and nut steering
r V-8 models 154Oib

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Steering and Wheel Alignment
Steering system warnings and cautions
WARNING -
The BMW airbag system is complex. Special precautions
must be observed when servicing the system. Serious in-
jury may result if system service is attempted by persons
unfamiliar with the BMW
airbag system and its approved
service procedures. BMW specifies that all inspection and
service should be
peiformed by an authorized BMW deal-
e,:
The BMW E39 is equipped with an airbag mounted in
the steering wheel. The
airbag is an explosive device
and should be treated with extreme caution. Always fol-
low the
airbag removal procedure as outlined in 721
Airbag System (SRS).
BMW airbags are equipped with a bacli-up power sup-
ply inside the
airbag control module. A 5 second wait-
ing period should be observed after the battery cable
has been disconnected. This will allow the reserve
power supply to discharge.
Do not reuse self-locking nuts. They are designed to
be used only once and may fail if reused. Always re-
place them with new locliing nuts.
* Do not install bolts and nuts coated with undercoating
wax, as correct tightening torque cannot be assured.
Always clean the threads with solvent before installa-
tion, or install new parts.
Do not attempt to weld or straighten any steering com-
ponents. Always replace damagedparts.
CAUTION--
- Some E39 models are equipped with aluminum suspen.
sion components. The following cautions apply:
Due to the chemical and corrosion characteristics of
aluminum, do not bring into contact with battery acid.
Do not clean with wire brushes with brass or iron bris-
tles. Only use brushes with stainless steel bristles.
Do
not expose to flying sparks from grindinghutting op-
erations.
Do not subject to steel welding splashes.
* Do not expose to temperatures over 80% (176°F).
even for short periods. Temperatures in painting iacili-
ties are not a problem.

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320-7
Steering and Wheel ~liqnmentl
STEERING WHEEL
Steering wheel, removal and installation
WARNING -
The BMWairbag system (Supplemental Restraint System or
SRS) is complex. Special precautions must be observed
when servicing. Serious injury may result if
SRS system serv-
ice is
attempted by persons unfamiliar with the BMW SRS
and its approved service procedures. BMW specifies that all
inspection andservice should be preformed by an authorized
BMW dealer.
E39 cars may come with either one of two different styles of
steering wheel:
Multifunction (MFL) steering wheel
* Sport steering wheel
4 Multifunction (MFL) steering wheel components:
1. Cruise control 1 radio 1 telephone electrical harness
2. Horn button electrical harness
3. Airbag electrical harness
4. Radio / telephone control switch set
5. Air bag
6. Cruise control switch set
Sport steering wheel
3
5 0021413
4 Sport steering wheel components:
1. Switch carrier
2 Steering wheel switch set electrical harness
3. Airbag
4. Lower cover
5. Horn button and airbag electrical harness
- Center steering wheel. Make sure front wheels are pointed
straight ahead.
- Disconnect negative (-) cable from battery.
CA UTIOP&
Prior to disconnecting the battern read the battew discon-
nection cautions given in
001 General Cautions and
Warnings.
-

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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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Check for proper alignment of steering column marks (ar-
row) before removing steering wheel.
NOTE-
The steering column and steering wheel are match marked
at the factory
Remove lower steering column trim panel. See Steering col-
umn trim, removing
and replacing.
Working underneath steering column, disconnect electrical
harnesses (A) and
(B).
Remove steering wheel.
When reinstalling steering wheel:
Align steering wheel and column match
marks.
Align steering wheel to alignment pins located on steering
column switch block.
Install steering column center bolt. Do not over-torque.
Carefully install
airbag. See 721 Airbag System (SRS).
Tightening torques
Steering wheel to steering
shaft (M14) 63 Nm (47 ft-lb)
Airbag to steering wheel (MFL only) 8 Nm (6 ft-lb)

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I Steering and Wheel Alignment
- Installation is reverse of removal, noting the following:
Replace shear bolts at steering column mounting bracket.
Tighten until bolt heads shear off.
Make sure
interlock cable snaps into place.
When installing column top trim panel, replace expansion
nut for trim retaining screw.
NOTE-
The steering angle sensor must be coded using a BMW scan
tool if it has been replaced.
A steering angle offset check
must then be carried out using the same
BMW scan tool.
CAUTION-
Check steering system for freedom of movement through en-
tire steering column
adiustment range.
Tightening torques Steering shaft coupler
to steering shaft 25 Nm (18 ft-lb)
(replace bolt)
Steering column to body
22 Nm (16 ft-lb)
Steering column adjustment motors,
removing and installing
Remove lower dash panel mounting fasteners (A) and (B).
- Lower panel and disconnect wiring harness from back side.
- Remove steering column lower trim panel. See Steering col-
umn trim, removing and replacing.
- Disconnect electrical harness from motor.
Remove motor mounting fasteners (arrows)
Slide motor to side and forward to remove.
Installation is reverse of removal.

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-
-steering and wheel -. Alignment I
< Hand tighten rear suppoll nut (arrow) against mounting
bracket.
Install rear mounting nut and tighten.
Do not over-torque banjo bolts.
* Fill and bleed power steering system as described later.
Tightening torques
Hydraulic lines to steering pump (banjo bolts)
a MlO 12 Nm (9 ft-lb)
. M14 35 Nm (26 ft-lb)
MI6 40 Nm (30 ft-lb)
. MI8 45 Nm (33 ft-lb)
Pump
brackets to engine block 25 Nm (18 ft-lb)
Rear pump support stud to pump housing
22 Nm (16 ft-lb)
Power steering system, bleeding and filling
- With engine off, fill power steering fluid reservoir with clean
fluid. Fill level to MAX
mark on dip stick.
- Start engine. Turn steering wheel twice to left lock and right I
lock.
- Recheck fluid level with engine off. Fill to MAX.