1997 BMW 540i Tire

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330-23
Rear Suspension
Remove rear control arm:
Remove inner control arm bolt
(A).
Detach plastic wiring harness support (B).
* Remove outer control arm ball joint nut (C). Press ball joint
out of rear wheel bearing carrier.
Installation is reverse of removal, noting the following:
Always use new self-locking nuts.
Malte sure all threaded bolts, nuts and mating surfaces are
clean.
Inner control arm mounting bolt must thread to rear (bolt
head at front).
Tighten fasteners to final torque only afler vehicle has
been lowered and suspension has settled.
Have car professionally aligned when job is complete.
Tightening
torques
Control arm to subframe (M12) 110 Nm (81 ft-ib)
Control arm
ball joint to wheel bearing 142 Nm (105 ft-lb)
carrier
(M14)
Quick coupling screw to air shock absorber
2 Nm (18 in-lb)
Road wheel
to hub 120-flONm
(89 i7 ft-lb)
Upper rear control arm, removing and
installing (Sport Wagon models)
CAUTIOG
Disable air supply pump by disconnecting electrical plug be-
fore
perlorming any repairs. Pump is located beneath a cover
under the spare tire in the floor of the
carqo compartment.
- Raise rear end of car and remove wheel.
WARNING -
Make sure the car is firmly supported on jaclc stands de-
signed for the purpose.
Place jaclc stands underneath struc-
tural chassis points. Do not place jack stands under
suspension parts.
Models with rear coil springs: Remove cargo compartment
floor carpet.
Worlting at top of coil spring, press center cap down or pry
upward to remove. If pushed down, remove from inside coil
spring from under car.

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Rear Suspension
- Remove exhaust system. See 180 Exhaust System.
- Detach driveshaft from differential. See 260 Driveshaft.
- Remove brake caliper and brake disc. Hang brake caliper
aside with stiff wire. Do not disconnect brake fluid hose. See
340 Brakes.
- Remove left and right ABS sensors from wheel bearing car-
riers.
Disconnect parking brake cable from brake shoe expander.
See 340 Brakes.
Remove heat shield from above driveshaft
If equipped, remove ride height sensor connectors
CAUTION-
Models with air springs: Disable air supply pump by discon-
necting electrical plug before performing any repairs. Pump is
locatedbeneath a coverunder
thespare tire in the floorof the
carqo compartment.
Models with air springs: Loosen compressed air pipes (ar-
rows) at air distribution assembly to release system pres-
sure.
WARNING -
Vehicle will lower when the air pipes are opened. 1
- 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.
4 Support final drive unit from below using transmission jack
(BMW special tools 00 2 030 and 33 4 390 or equivalent).
NOTE-
Special tool 33 4 390 will need modifications to cradle the fi-
nal drive properly
4 Remove right and left suspension trim panels (arrow),

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330-35
Rear Suspension
- Remainder of installation is reverse of removal, noting the fol-
lowing.
Always use new self-loclting nuts.
Make sure all threaded bolts, nuts and mating suriaces are
clean.
Make sure long lower strut bushing fits in hole in wheel
bearing carrier.
Tighten fasteners to final torque only after vehicle has
been lowered and suspension has settled.
Stake axle collar nut after tightening.
Tightening torques
ABS pulse sensor to wheel bearing carrier
8 Nm (6 ft-lb)
Brake rotor to hub 16 Nm (12 ft-lb)
Rear brake pad carrier (caliper) to wheel 65
Nm (48
ft-lb)
bearing carrier
Rear axle shaft to hub
(M27) 300 Nm (221 ft-lb)
Rear strut to wheel bearing carrier 127
Nrn (94 ft-lb)
Road wheel to hub
120+10 Nm
(89
i7 ft-lb)
Swing arm to wheel bearing carrier 256
Nrn (189 ft-lb)
Upper front control arm (traction strut) to 65 Nrn
(48
ft-lb)
wheel carrier
Upper rear control arm to wheel carrier 142
Nrn (105
ft-lb)
Rear wheel bearing carrier, removing and
installing (Sport Wagon models)
- Raise rear end of car and remove wheel.
WARNING-
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 jack stands under
suspension parts.
Models
with air springs: Disable air supply pump by discon-
necting electricalplug
beforepedormingany repairs. Pump is
located beneath a cover under the spare tire in the floor of the
cargo compartment.
-- 4 Models with air springs: Loosen compressed air pipes (ar-
rows) at air distribution assembly to release system pres-

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---
Rear Suspension
ELECTRONIC HEIGHT CONTROL
(EHC) COMPONENT REPLACEMENT
Sport Premium rear suspension is an option on Sport Wagon
models and standard on
1999 and later V-8 Sport Wagons.
This suspension incorporates electronic height control
(EHC)
using air springs.
With vehicle lifted off the ground,
if the rear air springs can be
compressed by hand, either the spring is defective or the sys-
tem is depressurized.
Locate
EHC faults using BMW scan tools DIS or MoDiC. EHC
description and some troubleshooting is covered in 300 Sus-
pension, Steering and Brakes-General.
Air spring replacement is covered earlier in this chapter. See
Air spring, removing and installing.
CAUTION-
Maintain high levels of cleanliness around air line connec-
tions when disassembling and assembling air suspension
components. Even
small dirt particles can cause leakage in
the pressurized system.
Electronic height control
(EHC) components
1. Air spring
2. 1 liter air reservoir
3. EHC control module
4. Air supply distributor
5. Airsupply pump
(under spare tire)
6. Air spring mounting bolt
(at wheel bearing carrier)
7. Rear ride height sensors
(Hall effect)
8. Air supply pump relay

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-- I
I: ... . -. Rear Suspension! -- .- -
Air compressor pump relay, removing and
installing
- Working in cargo compartment, remove spare wheel.
4 Remove air supply pump fasteners (arrows). Turn pump
over.
- Turn relay plug 45" and remove relay.
EHC control module, removing and
installing
The EHC control module is mounted on the right side of the
spare tire
well in the cargo compartment.
- Remove spare tire.
4 Remove electrical components cover (A).
- Release control module wiring harness plug loclting clip (B)
and remove module.
- Installation is reverse of removal.
- After assembly, reset ride height using BMW diagnostic scan
tool DIS.
Air supply unit, removing and installing
CAUTION-
Maintain high levels of cleanliness around air line connec-
tions when disassembling and assembling air suspension
components. Even small dirt particles can cause
leakage in
the pressurized system.
When the airsupply unit is removed for any reason, reset ride
height using BMW scan tools DIS or
MoDiC.
- Remove spare tire.
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Final ~rivel
4 Remove staked collar nut and press output shafl out of wheel
hub with special
BMW tool 33 2 111/116/117.
- Remove drive axle.
- Installation is reverse of removal, noting the following:
Use a new collar nut.
a Apply a light coating of oil to contact face of collar nut and
install it loosely.
* Install road wheel and lower car to ground.
- With an assistant applying brakes, tighten drive axle collar
nut to its final torque.
Stake collar nut.
Tightening torques
-
Drive axle collar nut to drive flange M27 300 Nrn (221 ft-lb)
Drive axle to differential flange
* M10x20 rnm black Torx bolt
83 Nrn (61 ft-lb)
M10x20 rnrn silver Torx bolt
100 Nrn (74 ft-lb)
Road wheel to hub 120 Nrn f 10 (89 ft-lbf7)
Drive axle, removing and installing
(Sport Wagon)
4 With an assistant applying brakes, brealc free staked collar
nut (arrow) at center of rear wheel hub. Do not remove com-
pletely.
NOJE-
The drive flange collar nut is tightened to a torque of over 300
Nm (221 ft-lb). Make sure the car is firmly on the ground.
WARNING -
Disable airsupply pump (if applicable) by disconnecting elec-
tricalplug before performing any repairs. Pump is located be-
neath a cover under the spare tire
in the floor of the cargo
compartment.
- Raise rear of car. Remove rear wheel.
WARNING -
Malce sure that the car is firmly supported on jack stands de-
signed for the purpose. Place the jack stands beneath struc-
tural chassis points. Do not place jack stands under
suspension parts.
- Models with rear coil springs: Remove cargo compartment
floor carpet.

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Brakes
Troubleshooting
Brake performance is mainly affected by three things:
Q Level and condition of brake fluid
Ability of bralte system to create and maintain pressure
Condition of friction components
Air in bralte fluid will
make the brake pedal feel spongy during
braking
orwill increase the bralte pedal force required to stop.
Fluid contaminated by moisture or dirt can corrode the sys-
tem. lnspect the brake fluid inside the reservoir. If it is dirty or
murky, or is more then two years old, replace fluid.
To
check the function of the master cylinder hold the bralte
pedal down hard with the engine running. If the pedal slowly
falls to the floor, either the master cylinder is leaking internal-
ly, or fluid is leaking externally.
lnspect the rotors for glazing, discoloration and scoring.
Steering wheel vibration while braking at speed is often
caused by warped rotors, but can also be caused by worn
suspension components.
When troubleshooting, keep in mind that tire inflation, wear
and temperature can all have an affect on braking. See
300
Suspension, Steering and Brakes-General for additional
suspension and brake system troubleshooting.
The table Brake system troubleshooting lists symptoms of
brake problems, probable causes, and suggested corrective
actions. Unless noted otherwise, relevant repairs are de-
scribed later in this repair group.

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340-6
1 Brakes
Brake system troubleshooting
/symptom I Probable cause 1 Repairs
Brake squeal
Pedal goes to floor when
bralting
Low pedal after system bleeding
Pedal spongy or brakes work
only when pedal is pumped
Excessive braking effort
Brakes pulsate, chatter or grab
Uneven
bralting, car pulls to one
side, rear braltes
loclt
Brakes drag, bind or overheat Brake
pad carriers dirty or corroded or
pads loose (poor fit) in pad carrier
Braite pads heat-glazed or oil-soaked
Wheel bearings worn (noise most
pronounced when turning)
Incorrectly Installed brake pads,
parking bralte shoes, or bralte parts
Brake fluid loss due to system leaks
Master cylinder or traction control
system faulty
Master cylinder faulty
Air in braite fluid
Master cylinder or traction control
system faulty
Brake pads wet
Brake pads
heat-glazedorfluid-soalted
Vacuum booster or vacuum hose
connections to booster faulty
--- Warped brake rotors
Brake pads worn
Brake pads heat-glazed or oil-soaked Remove
brake pads and clean calipers. Use original
equipment pads for proper fit and use BMW anti-squeal
compound during installation,
Replace brake pads. Ciean rotors. Replace leaking caliper:
as required.
Replace worn bearings. See 310 Front Suspension
or33C
Rear Suspension.
Check component installation. Checldreplace anti-rattle
springs.
Checlt fluid level and inspect for signs of leakage.
Replace master cylinder. Diagnose traction control system
using factory or compatible diagnostic tool.
Replace master cylinder.
Bleed system using factory or compatible diagnostic tool.
Replace master cylinder. Diagnose traction control system
using factory or compatible diagnostic tool.
Use light pedal pressure to dry pads while driving.
Replace
bralte pads and rotors. Replace leaking calipers.
lnspect vacuum lines. Test vacuum booster and replace as
required. Test vacuum non-return valve for one-way flow.
Resurface or replace rotors.
Replace brake pads.
Clean rotors. Replace leaiting calipers.
Incorrect tire pressures or worn tires
Brake pads on one side of car heat-
glazed or fluid-soaked
Caliper or brake pads binding
Worn suspension components
Brake caliper or brake pads binding
Master cylinder or traction control
system faulty lnspect
tire condition. Checlt and correct tire pressures.
Replace brake pads. Clean rotors. Replace leaking
calipers.
Clean and recondition brakes.
Inspect for worn or damaged suspension components. See
310 Front Suspension or 330 Rear Suspension.
Ciean or replace caliper.
Replace master cylinder. Diagnose traction control system
using faclory or compatible diagnostic tool.