1998 BMW 540i Ac system

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Rear Suspension Swing arm, 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.
CAUJION-
Model with air springs: Disable air supply pump by discon-
necting electricalplug
beforeperforminganyrepairs. Pump is
located beneath a cover under the spare tire in the floor of the
cargo compartment.
< Model with air springs: Loosen compressed air pipes (ar-
rows) at air distribution assembly to release system pres-
sure.
NOJE-
Vehicle will stand quite low
- If applicable: Detach air supply line from shock absorber.
Plug ports and lines to
lkeep out dirt.
- Model with rear coil springs: Remove cargo compartment
floor carpet.
4 Working 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.
4 Working from underneath, position BMW special tool
33
2 301 between 2nd and 3rd spring coil from bottom.
Make sure tool recess faces upward.
Working in cargo compartment, guide BMW special tool
33
2 304 from above and thread into special tool 33 2 301.

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330-1 9
Rear suspension1
Swing arm ball joint, replacing
- Raise rear end of car and remove wheel.
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.
- Sport Wagon model: Support wheel bearing carrier from be-
low.
CA
UTION-
The shock absorberprevents the drive axle and wheel bear-
ing carrier from dropping too far. Supporting the wheel bear-
ing carrier before disconnecting the
shoclc absorber
mounting fastenerprevents damage to the brake hose, park-
ing
brake cable and drive axle CVjoints.
- Model with air shock absorbers: Detach air supply line from
shoclc absorber. Plug ports and lines to keep out dirt.
- Sport Wagon model: Remove shock absorber lower mount-
ing bolt.
4 Remove stabilizer bar link mounting nut (arrow). Press link
out of swing arm.
Model with air springs: Disable air supply pump by discon-
necting electrical plug before performing any repairs. Pump is
located beneath a cover under
the spare tire in the floor of the
carao
comoartment.
4 Model 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.
- Models with rear coil springs: Remove cargo compartment
floor carpet.

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330-24
Rear Suspension
4 Working from underneath, position BMW special tool 33 2
301 between 2nd and 3rd spring coil from bottom.
Make sure tool recess faces upward.
Working in cargo compartment, guide BMW special tool 33
2 304 from above and thread into special tool 33 2 301.
4 Working in cargo compartment, attach BMW special tools 33
2 302, 33 2 303 and 33 2 305 to special tool 33 2 304.
Use special tool 33
2 306 to compress spring.
Tighten until lower spring coil lifts off spring seat on wheel
bearing carrier.
4 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
- Support wheel bearing carrier from below.
CAUTION-
The shock absorber prevents the drive axle and wheel bear-
ing carrier from dropping too far. Supporting the wheel bear-
ing carrier before disconnecting the shock absorber
mounting iastenerprevents damage to the brake hose,
parl-
ino brake cable and drive axle CV ioints.
- Models with air shock absorbers: Detach air supply line from
shock absorber. Plug ports and lines to keep out dirt.
- Remove shoclc absorber lower mounting bolt

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330-26
/ Rear Suspension
Remove inner control arm eccentric nut and bolt (A)
Remove control arm ball joint nut (6). Press ball joint out
of wheel bearing carrier.
Lifl out control arm.
Installation is reverse of removal, noting the following:
Use previously made
marks to install eccentric bolt and
nut.
Always use new self-locking nuts.
Tighten fasteners to final torque only after vehicle has
been lowered and suspension has settled.
0 Have car professionally aligned when job is complete.
Tightening
torques
Road wheel to hub 120klONm
(89 i7 ft-lb)
Upper front control arm (traction strut) to 60
Nm (44
ft-lb)
subframe (rear toe adjusting bolt)
Upper front control arm (traction strut) to wheel
65 Nm (48 ft-lb)
carrier
Rear axle assembly, removing and
installing (sedan models)
In case of damage to the subframe, or if a pressed-in bushing
is worn, remove
subframe by removing complete axle assem-
bly.
- Raise car and remove rear wheels.
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.
- 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 lefl 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.

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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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