1998 BMW 540i Power steering fluid

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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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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 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

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Steering and Wheel ~li~nrnentl
Steering gearbox, removing and installing
- Disconnect negative (-) battery cable. See 020 Mainte-
nance.
CAUTION-
Prior to disconnecting the battew read the battery discon-
nection cautions given in
001 General Cautions and
Warnings.
- Remove airbag unit from steering wheel. See 721 Airbag
System (SRS).
WARNING -
Improper handling of the airbag could cause serious injury
Store the
airbag with the horn pad facing up. If stored lacing
down, accidental deployment couldpropel it violently info the
air, causing
injuv
- Remove steering wheel as described earlier.
- Drain power steering system reservoir.
- Raise front of car.
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 heat shield from left side of subframe.
- Remove fluid hoses from top of steering gearbox. Immedi-
ately plug all fluid openings.
Remove and discard
pitman arm self-loclting nut (arrow).