1998 BMW 540i Power steering

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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
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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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.

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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.

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i Steering and Wheel Alignment
RACK AND PINION STEERING
(6-CYLINDER MODELS)
Refer to the steering components illustration when perform-
ing the procedures below.
Rack and pinion steering
components
(6-cylinder models)
1. Power steering fluid reservoir
2. Fluid supply line
3. Power steering pump
4. Copper sealing ring
5. Banjo bolt MI4
6. Banjo bolt MI6
7. Power steering rack
8. Fluid return line
9. Pressurized fluid line
10. Steering fluid cooler
11. Rack boot components
12. Tie rod nut
13. Washer
14. Outer tie rod end
15. Tie rod locking ring
16. Outer tie rod end loclc nut
17. Inner tie rod
18. Hydraulic control valve
Steering rack, removing and installing
- Remove steering wheel as described earlier.
- Raise front of car, and remove front wheels.
WARNING -
Male 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
parts.
- Remove splash shield from under engine.
- Remove right and lefl engine mount fasteners
-" ., - , . ,

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/steering and Wheel Alignment
Raise engine approximately 40 mm (1.6 in). See 110 Engine
Removal and installation.
Remove right and left engine mounts and remove mount
brackets from subframe.
Empty power steering fluid reservoir using a clean syringe.
Do not reuse power steering fluid.
Remove right tie rod fastener (arrow) from right steering
Itnuckle. Repeat for left.
4 Press right tie rod out of right steering knucltle using BMW
special tool 31
2 240. Repeat for left.
/ ~ock nut Loclting ring
0012143
4 Malte reference measurement (A) of right tie rod end to tie
rod. Record measurement. Repeat for left.
NOJE-
0 Accurate measurement of tie rod end with reference to tie
rod will help approximate correct wheel alignment during
reassembly.
Note correct placement of inner taper on
locling ring
Remove fluid line
banjo bolts (arrows)
from steering rack.

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Steering and Wheel ~lignmentl
Remove lower steering column flexible joint pinch bolt (ar-
row). Pull flexible joint off steering rack shaft.
Remove steering rack mounting bolts. Remove steering
raclc
from subframe by pulling it to left.
Installation is reverse of removal, noting the following:
Make sure all thread bores, bolts, nuts, splines and mating
surfaces are clean.
Use new steering rack mounting bolts. Tighten in two stag-
es. Note tightening instructions in torque table below.
Use anti-seize paste on inner tie rod threads.
Use new self-loclting nuts wherever applicable.
Use keved
comDonents to reassemble steerino column
flexible\oint to ;teering raclt shaft. u
Use new bolt at steering shaft coupling.
Use new sealing O-rings on banjo fittings.
Do not over-torque banjo bolts.
Fill and bleed power steering system as described earlier.
Use tie rod measurement previously made (measurement
A) to temporarily set toe.
Have car professionally aligned.
Tightening torques Hydraulic lines to steering rack (use new O-ring
seals)
M14 banjo bolt 35 Nrn (26 ft-lb)
. M16 banjo bolt 40 Nm (30 ft-lb)
Steering shaft coupling
to rack (use new bolt) 19 Nm (14 it-lb)
Steering rack to subframe (use new bolts)
- initial torque 50 Nm (37 ft-lb)
Torque angle 90"
Tie rod
to Steering knuckle (replace self-locking
65 Nm (48 ft-lb)
nut)
- to Steering rack 71 Nm (52 ft-ib)
Outer tie rod end lock nut
51 Nm (38 ft-lb)

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Steering and Wheel Alignment
Tightening torques
Tie rod
to Steering knuckle (replace self-locking nut) 65 Nm (48 it-lb)
to Steering rack 71 Nrn (52 ft-lb)
Outer tie rod end lock nut 51 Nrn (38 ft-lb)
Refer to the steering components illustration when perform-
ing the procedures below.
Steering gearbox system
components
(V-8 models
up to
911 999)
1. Tie rod end nut
2. Washer
3. Tie rod end
4. Steering fluid cooler
5. Tie rod end clamp bolt
6. Nut
7. ldler arm
8. ldler arm bushing
9. ldler arm bolt
10. Steering fluid reservoir
11. Hose clamp
12. Fluid supply line
13. Power steering pump
14. Fluid return line
15. O-ring seal
16. Banjo bolt
17. High pressure line
18. Center tie rod
19. Nut
20. Pitman arm
21.
Pitman arm pinch bolt
22. Nut
23. Fluid cooler supply line
24. Steering gearbox