1997 BMW 318i Iat sensor

Wheel
brake
caliper

Electronic
control
module
Fig
.
4
.



Schematic
representation
of
ABS
.

SUSPENSION,
STEERING
ANDBRAKES-GENERAL



300-3

Fig
.
3
.



Schematic
view
ofdual
circuit
brakes
with
4-channel
ABS
.

ing
adverse
conditions
.
It
automatically
adjusts
brake
system
hydraulic
pressure
at
each
wheel
to
prevent
wheel
lock-up
.

The
system's
main
components
arethe
wheel
speed
(pulse)
sensors,
the
ABS
control
module,
and
the
hydraulic

control
unit
.
See
Fig
.
4
.

Warning
lamp

u
Master

Whee

_

l
speed



I-lydraulic



cylinder

sensor



control
unit



0012135

UNI

The
wheel
speed
sensors
continuously
send
wheel
speed
signals
to
the
control
module
.
See
Fig
.
5
.
The
control
module
compares
these
signals
to
determine,
in
fractions
of
a
second,
whether
any
of
the
wheels
areabout
to
lock
.
If
any
wheel
is
nearing
a
lock-up
condition,
the
module
signals
the
hydraulic
unit
to
maintain
or
reduce
pressure
at
the
appropriatewheel(s)
.
Pressure
is
modulated
by
electrically-operated
sole-

noid
valves
in
the
hydraulic
unit
.

Fig
.
5
.



ABS
wheelspeed
sensor
.

0006563

INTEGRATED
SYSTEMS

310-
8



FRONT
SUSPENSION

FRONT
WHEEL
BEARINGS

The
front
wheel
bearings
are
permanently
sealed
and
re-

quire
no
maintenance
.
The
bearing
is
integral
with
the
wheel

hub
and
pressed
onto
the
steering
arm
stub
axle
.

Special
press
tools
are
requiredto
replace
the
front
wheel

bearings
.
Read
the
procedure
through
before
beginning
the

job
.

Front
wheel
bearing,
replacing

1
.
Raise
car
and
remove
wheel
.

WARNING-

Make
sure
that
the
car
is
firmly
supportedon
jack

stands
designed
for
the
purpose
.
Place
the
jack

stands
beneatha
structural
chassis
point
.
Do
not

place
jack
stands
under
suspension
parts
.

2
.
Pry
off
dust
cap
from
centerof
wheel
hub
.
Bend
back

staked
part
of
wheel
hub
(axle)
collar
nut
.
See
Fig
.
13
.

Fig
.
13
.
Staked
part
of
wheel
hub
collar
nut
to
be
bent
back
(arrow)
.

3
.
Remount
wheel
and
lug
bolts
.

4
.
Lower
canto
ground
.
With
an
assistant
applying
brakes,

loosen
collar
nut
.
Do
not
remove
completely
.

NOTE-

The
wheel
hub
collar
nut
is
tightened
to
a
torque
of
290
Nm
(214
ft-Ib)
.
Make
sure
the
car
is
firmly
on
the
ground
.

FRONT
WHEEL
BEARINGS

6
.
Remove
ABS
wheel
speed
sensor
.
Refer
to
Fig
.
3
.

7
.
Remove
brake
caliper
assembly
and
brake
rotor
as
de-

scribed
in
340
Brakes
.
Leave
brakehose
connected
to

caliper
.
Suspend
caliper
assembly
from
chassis
using

stiff
wire
.

8
.
Remove
wheel
hub
collar
nut
.

9
.
Remove
wheel
hub
with
integral
wheel
bearing
from

steering
arm
using
a
puller
.
See
Fig
.
14
.

0011200

Fig
.
14
.
Wheel
hub
with
integral
wheel
bearing
being
removed
using
a

puller
.

NOTE-
If
bearing
inner
race
stays
on
steering
arm,
remove
splash
guard
and
usetwo
jaw
puller
to
remove
race
.

10
.
Insta¡¡
splash
guard
and
new
dust
shield
behind
bear-

ing
.
Press
new
wheel
hub/bearing
assembly
on
using

appropriate
press
tools
.

NOTE-

When
pressing
the
wheel
hublbearing
on,
apply
force
only
to
the
bearing
inner
race
.

11
.
Install
new
collar
nut
.
Do
not
tighten
nut
to
its
final

torque
atthis
time
.

"
Install
brake
rotor
and
brake
caliper
.
See
340
Brakes
.

"
Mount
wheel
and
lug
boits
.
Lower
canto
ground
to
gain

leverage
.

12
.
With
an
assistant
applying
brakes,
tighten
collar
nut

and
then
stake
nut
toaxle
.

5
.
Raise
car
and
remove
wheel
.



13
.
Raisecar
and
remove
wheel
.

Wheel
bearing

Fig
.
7
.



Rear
wheel
bearing
assembly
.

Circlip



Drive
flange



Collar
nut

0012152

Rear
wheel
bearing,
replacing

1
.
Raise
car
and
support
safely
.
Remove
rear
wheel
.

2
.
Remove
drive
axle
as
described
later
.



6
.
Remove
bearíng
retainer
circlip
from
trailing
arm
.

3
.
Remove
brake
caliper
assembly
and
rotor
as
described



7
.
Using
appropriate
press
tools,
pull
bearing
assembly

in
340
Brakes
.
Leave
brake
hose
connected
to
caliper
.



out
of
trailing
arm
bearing
housing
.

Suspend
caliper
assembly
from
chassís
using
stiff
wire
.

8
.
Inspect
bearing
housing
for
any
damage
or
contamina

4
.
Remove
ABS
pulse
sensor
.
See
Fig
.
8
.



tion
.
Clean
housing
bore
thoroughly
before
installing

new
bearing
.
Make
sure
al¡
thread
bores,
bolts,
nuts

and
mating
surfaces
are
clean

Fig
.
8
.



ABS
pulse
sensor
being
removed
.

5
.
Remove
drive
flange
from
bearing
assembly
.
See
Fig
.

9
.

NOTE-

If
the
inner
bearing
race
remains
attached
to
the
drive

flange,
use
BMW
special
tool
nos
.
007
500
and
33
1

312
or
equivalents
to
separate
inner
race
from
flange
.

REAR
SUSPENSION



330-
5

0013125

Fig
.
9
.



Drive
flange
being
removed
from
bearing
assembly
using
im-
pact
style
puller
.

9
.
Install
new
bearing
assembly
using
press
tools
.
Apply

force
only
to
outer
race
when
installing
bearing
.

WARNING
-

M3
installation
:
redsealing
ríng
on
rear
wheel
bear-

ing
must
face
outward
.
Otherwíse
ABS
will
not
func-
tion
.

10
.
Insta¡¡
new
circlip
.
The
old
circlip
should
never
be
re-

used
.

CAUTION-

Make
sure
that
the
bearing
is
pressed
in
far
enough
to
contact
the
shoulder
at
the
back
sideof
the
housing
and
that
the
circlip
is
fully
seated
in
its
groove
.

11
.
Draw
drive
flange
into
bearing
using
appropriate
press

tools
.
Support
bearing
inner
race
when
pressing
in

0013223



drive
flange
.

NOTE-

BMW
specifies
special
tools
to
pull
the
drive
fiange
through
the
wheel
bearing
into
position
.
If
using
alter-
native
tools,
be
sure
to
support
the
bearing
inner
race
when
pressing
orpulling
the
drive
flange
finto
place
.

REARWHEEL
BEARINGS

Brake
rotor,
removing
and
installing
.
.
.
.
.
.
.
.
340-7

MASTER
CYLINDER
............
.
.
.
.
.
.
.340-7

Master
cylinder,
removing
and
installing
.
...
.
340-7

GENERAL



TROUBLESHOOTING

WARNING
-

"
Although
semi-metallic
and
metallic
Brake
friction
materials
in
Brake
pads
or
shoes
no
longer
con-
tain
asbestos,
they
produce
dangerous
dust
.
"
Brake
fluid
is
poisonous,
highly
corrosive
and
dangerous
to
the
environment
Wear
safety
glasses
and
rubber
gloves
when
working
with
Brake
fluid
.
Do
not
siphonBrake
fluid
with
your
mouth
.
Immediately
clean
away
any
fluid
spilled
on
painted
surfaces
and
wash
with
water,
asBrake
fluid
will
remove
paint
.

"
Always
use
new
Brake
fluid
froma
fresh,
un-
opened
container
.
Brake
fluid
will
absorb
mois-
ture
from
the
air
.
This
canlead
to
corrosion
problems
in
the
brakingsystem,
and
will
also
low-
er
the
Brake
fluid's
boiling
point
.
Dispose
of
Brake
fluid
properly
.

"
Do
notreuse
self-locking
nuts,bolts
or
fasteners
.
They
are
designed
to
be
used
only
once
and
may
failif
reused
.
Always
replace
them
with
new
self-
locking
fasteners
.

BMW
E36
models
areequipped
with
vacuum
power-assist-

ed
four-wheel
disc
brakes
with
an
integral
Antilock
Brake
Sys-

tem
(ABS)
.
Single-pistoncalipers
act
on
solid
or
vented
front
rotors
and
solid
rear
rotors
.
A
brake
pad
wear
sensor
for
each

axle
indicates
when
brake
padsneed
replacement
.
The
dual

drum-type
parking
brakesystem
is
integrated
with
the
rear
brake
rotors
.

NOTE-

M3
models
havevented
directional
Brake
rotors
on
the
rearaxle
as
well
ason
the
front
.

340
Brakes

BRAKES
340-1

GENERAL
.
.
.
.
.
.
.........
.
.
.
..........
340-1



BRAKE
BOOSTER
.........
.
.
.
.
.
...
.
.
.
.
340-8

TROUBLESHOOTING
.......
.
......
.
...
340-1



Brake
booster,
removing
and
installing
....
.
.
340-8

PARKING
BRAKE
.
.....
.
...
.
.
.
.....
.
.
.
340-10
BLEEDING
BRAKES
.
.
.
.
.
.
.
.
..........
340-3



Parking
brake,adjusting
.
.
.
.
.
.
.
.
.
.
.....
.
340-10
Pressure
bleeding
brakes



Parking
brake
shoes,
removing
and
installing
.
340-11(except
cars
with
AST)
.
.
.
.
.
.
.
.
.
...
.
.
.
.
.340-3



Parking
Brake
cable,
replacing
.
.
.
.
.
.
.
.
.
.
.
.
340-11

BRAKE
PADS,
CALIPERS,



ANTILOCK
BRAKE
SYSTEM
(ABS)
.
.
.
.340-11
AND
ROTORS
..........
.
.......
.
.
.
.
.
.
.
340-3



ABS
System
Inspection
.
...
.
.......
.
.
.
..
340-12
Brake
pads,
replacing
............
.
.
.
.
.
.
.
340-4
ABS
wheel
speed
sensors,
replacing
.
.
.
.
..
340-12
Brake
caliper,
removing
and
installing
.
..
..
.
340-6

TABLES

a
.
Brake
System
Troubleshooting
.....
...
.
.
.....
.340-2
b
.
Brake
Rotor
Reconditioning
Specifications
.
.....
.340-7

Brakeperformance
is
mainly
affected
by
three
things
:
the
leve¡
and
condition
of
the
brake
fluid,
the
system's
abilíty
to
create
and
maintain
hydraulic
pressure,
and
the
condition
of
the
friction
components
.

Air
in
the
Brake
fluid
will
make
the
Brake
pedal
feel
spongy

during
braking
or
will
increase
the
Brake
pedalforce
required

to
stop
.
Fluid
contaminated
by
moisture
or
dirt
can
corrode
the

system
.
Inspect
the
Brake
fluid
inside
the
reservoir
.
Ifit
is
dirty
or
murky,
or
is
over
a
year
old,
the
fluid
should
be
replaced
.

Visually
check
the
hydraulic
system
startingat
the
master

cylinder
.
To
check
the
function
of
the
master
cylinder
hold
the

brake
pedal
down
hard
with
the
engine
running
.
The
pedal

should
feelsolid
and
stay
solid
.
If
the
pedal
slowly
falls
to
the

floor,
either
the
master
cylinder
is
leaking
internally,
or
fluid
is
leaking
externally
.
If
no
leaks
canbe
found,
the
master
cylin-
der
is
faulty
and
should
be
replaced
.
Check
all
Brake
fluid
lines

and
couplings
for
leaks,
kinks,
chafing
and
corrosion
.

Check
the
Brake
booster
by
pumping
the
Brake
pedal
ap-

proximately
10
times
with
the
engine
off
.
Hold
the
pedal
down
and
start
the
engine
.
The
pedal
should
fa¡¡
slightly
.
If
not,
check

for
any
visiblefaults
before
suspecting
a
faulty
brake
booster
.

Check
for
strong
vacuum
at
the
vacuum
hose
fitting
at
the

booster,
and
check
the
non-retum
valve
for
one-way
flow
.

Worn
or
contaminated
brake
pads
will
cause
poor
braking

performance
.
Oil-contaminated
or
glazed
pads
will
cause

stopping
distances
to
increase
.
Inspect
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
byworn
suspension
components
.

TROUBLESHOOTING

6
.
Remove
brake
pads
from
caliper
.
Where
applicable,
carefully
pry
pad
wear
sensor
from
pad
.
See
Fig
.
5
.

Fig
.
5
.



Removing
brake
pad
wear
sensor
.

7
.
Inspect
brake
caliper
for
signs
of
leakage
.
Check
that
the
caliper
piston
slides
smoothly
into
caliper
.
Replace
caliper
if
any
faults
are
found
.

CAUTION-

With
the
pads
removed,
residual
hydreulic
pres-
sure
may
cause
the
caliper
piston
to
slide
out
.
Use
a
wooden
block
to
hold
the
piston
in
place
.

8
.
fnsert
brake
pad
wear
sensor
into
cutout
in
new
pad

where
applicable
.

14
.
Place
inner
brake
pad
(with
locating
spring)
ontobrake
NOTE-



caliper
piston
.
Route
pad
wear
sensor
wiring
through
lf
the
brake
lining
indicator
light
illuminated
prior
to



caliper
opening
and
bleeder
dust
cap
.
brake
pad
replacement,
the
wear
sensor
should
be
re-
placed
.



15
.
The
remainder
of
installation
is
reverse
of
removal
.

"
Do
not
lubricate
guide
boits
.
9
.
Slowly
press
piston
back
into
caliper
.
Use
cace
not
to



"
Once
brake
assembly
is
installed
depress
brakepedal
damage
piston
dust
sea¡
.
See
Fig
.
6
.



severa¡
times
before
driving
vehicle
.

NOTE-

"
Open
caliper
bleeder
screw
when
pressing
piston



Tightening
Torques

back
into
caliper
.
Catch
expelled
fluidin
appropriate



"
Brake
caliper
to
brake
pad

container
.
This
procedure
is
highly
recommended
in



carrier
(guide
bolt)
..........
...
.
.
30
Nm
(22
ft-Ib)

the
case
of
cars
with
ABS
.



"
Road
wheel
to
hub



.....
.
..
100±10
Nm
(74±7
ft-Ib)

"
Open
the
bleeder
screw
only
when
applying
force
to
the
piston
.
Do
not
allow
airto
be
drawn
in
through
the
bleeder
screw
.

"
Pressing
the
caliper
piston
in
may
cause
the
brake
flu-
id
reservoir
to
overflow
.
To
prevent
this,
use
a
clean
syringe
to
first
remove
some
fluid
from
the
reservoir
.

BRAKES
340-
5

0012157
Fig
.
6
.



Brake
caliper
piston
being
pressed
into
caliper
to
make
room
for
new
pads
.
Usea
rag
toprotect
caliper
piston
and
seals
.

10
.
Thoroughly
clean
inner
and
outer
surfaces
of
brake
ro-
tor
.
Inspect
rotor
for
cracks,
signs
of
overheating
and
0012156
scoring
.

11
.
Measure
thickness
of
rotor
.
See
Table
b
.
If
rotor
does
not
pass
minimum
thickness
requirements,
or
is
dam-

aged,
replace
as
described
later
.

12
.
Thoroughly
clean
all
contact
points
on
caliper
and
brake
pad
carrier
.
Clean
guide
bolts
and
make
surethey
slide
freely

13
.
Lightly
coat
pad
contact
points
with
brake
anti-squeal
paste
.
Place
outer
brake
pad
onto
caliper
.
Applya
small
amount
of
grease
to
thetop
and
bottom
contact
points
where
the
caliper
contacts
the
pad
carrier
.

BRAKE
PADS,CALIPERS,
ANDROTORS

Continuity,
checking
Short
Circuits

from
Battery

CAUTION-

Use
only
a
high
quality
digital
ohmmeter
having
high
input
impedance
when
checking
electronic
componente
.
The
internal
power
source
used
in
most
analog
(swing-need1e)
meterscan
damage
solidstate
components
.

0013239

Fig
.
2
.



Digital
multimeter
being
used
to
check
for
voltage
drop
across
a
switch
.

The
continuity
test
can
beused
to
check
a
circuit
or
switch
.
Because
most
automotive
circuits
are
designed
to
have
little

or
no
resistance,
a
circuit
or
part
of
a
circuit
canbe
easily

checked
for
faults
using
an
ohmmeter
.
An
open
circuit
or
a
cir-

cuit
withhigh
resistance
will
not
allow
current
to
flow
.
A
círcuit
with
little
or
no
resistanceallows
current
to
flow
easily
.

When
checking
continuity,
the
ignition
should
be
off
.
On
cir-
cuits
that
are
powered
at
all
times,
the
battery
should
be
dis-
connected
.
Using
the
appropriate
wiring
diagram,
a
circuit
can
be
easily
tested
for
faulty
connections,
wires,
switches,
relays,
and
engine
sensorsby
checking
forcontinuity
.
For
a
continu-
ity
check
on
a
brake
light
switch,
see
Fig
.
3
..

A
short
circuit
is
exactly
what
the
narre
implies
.
The
circuit
takes
a
shorter
paththan
it
was
designed
to
take
.
The
most

common
short
that
causes
problems
is
a
short
to
ground

where
the
insulation
on
a
positive
(+)
wire
wears
away
and
the

metal
wire
is
exposed
.
When
the
wire
rubs
against
a
metal

partof
thecar
or
other
ground
source,
the
circuit
is
shorted
to
ground
.
If
the
exposed
wire
is
live
(positive
battery
voltage),
a

Puse
will
blow
and
the
circuit
may
possibly
be
damaged
.

ELECTRICAL
SYSTEM
-
GENERAL
600-
5

Brake
light
switch

Brake
pedal
in
rest
position

Q

Brake
pedal
depressed
Brake
light
switch

Fig
.
3
.



Brake
light
switchbeing
tested
for
continuity
.
With
brake
ped-
alin
rest
position
(switch
open)
there
is
no
continuity
(infinite
ohms)
.
With
pedal
depressed
(switch
closed)
there
is
continu-
ity
(zero
ohms)
.

Shorts
to
groundcanbe
located
with
a
digital
multimeter
.
Short
circuits
are
often
difficult
to
locate
and
may
vary
in
na-
ture
.
Short
circuits
can
befound
using
a
logical
approach
based
onthe
current
path
.

CAUTION
-

"
On
circuits
protected
with
high
rating
fuses
(25
amp
and
greater),
the
wires
or
circuit
compo-
nents
may
be
damaged
before
the
fuse
blows
.
Always
check
for
damage
before
replacing
fuses
of
this
rating
.

"
When
replacing
blown
fuses,
use
only
fuses
hav-
ingthe
correct
rating
.
Always
confirm
the
correct
fuse
rating
printed
on
the
fuselrelay
panelcover

DC

ELECTRICAL
TROUBLESHOOTING

610-2



ELECTRICAL
COMPONENT
LOCATIONS

Fuses
number47
and
50are
mounted
on
the
left
side
splice

panel
.
Refer
lo
Fig
.
5
.

Fuse48
is
mounted
on
the
auxiliary
relay
panel
.
Refer
to

Fig
.
3
.

Fuse
49
is
mounted
in
the
right
side
of
the
luggage
compart-

ment
behind
the
trim
cover
.

Relay
Positions

Mounted
in
the
left-hand
rear
comer
of
the
engine
compart-

ment,
the
power
distribution
box
contains
46
(uses
and
15
re-

lay
positions
.
See
Fig
.
2
.

Fuses31-46

-
Er
a
&QT
MM
~

Fig
.
2
.



E36
front
power
distribution
box
.

FUSE
AND
RELAY
POSITIONS

Fuses1-20

13
EL1
5
]

mmmmmmmmmm
Fuses
21-30
--



0013034)

1
.
Fuel
pump
relay



9
.



Heater/A/C
Blower
relay
2
.
System
(main)
relay



10
.



Rear
defogger
relay
3
.
Oxygen
sensorheater
re-



11
.
ABS
system
relay
lay



12
.
ABS
pump
relay
4
.



Horn
relay



13
.



High
speed
radiator
fan
re-
5
.



Taillight/foglight
relay



]ay
6
.
Low
beam
relay



14
.
A/C
compressor
relay
7
.



High
beam
relay



15
.



Low
speed
radiator
fan
re-
8
.



Emergency
flasherrelay



¡ay

Auxiliary
Relay
Panel

The
auxiliary
relay
panel
contains
five
relay
positions
.
In
lat-

er
modeis
an
additional
fuse
holder
(Fuse48)
and
the
EWS
II
(anti-theft)
transmitter/receiver
module
are
located
on
this

panel
.
See
Fig
.
3
.

The
panel
is
located
nextto
the
steering
column
under
the
driver's
side
dashboard
.
To
access
this
panel,
remove
the
pwer
dash
panel
on
driver's
side
.
See513
Interior
Trim
.

Then
remove
the
driver's
side
knee
bolster
.
Lower
the
relay
panel
by
gently
releasing
the
plastic
retainers
.
See
Fig
.
4
.

During
installation,
be
sure
the
retainer
tabs
are
engaged
in
the
relay
panel
.

Splice
Panel,
Left

3

¡ni

Fig
.
3
.
Auxiliary
relay
panel
under
left
side
of
dash
.

Fuse
48)
0013035

1
.



Comfort
relay
(where
ap-



4
.



Not
used

plicable)



5
.



Not
used

2
.
Crash
control
module



6
.



EWS
II
transmitter/receiv-

3
.



Park
ventilation
relay



er
module
(from
Jan
.
1995)

0013164

Fig
.
4
.



Auxiliary
relay
panel
under
left
sideof
dashboard
(arrow)
.

The
left
splice
panel
contains
four
relay
positions
and
an
ad-
ditional
fuse
holder
(Fuses
47
and
50)
.

To
access
the
left
side
electrical
splice
panel,
remove
the

left
side
dash
panel
and
knee
bolster,
as
described
earlier
.

The
panel
is
located
above
and
lo
the
left
of
the
clutch
pedal
.

See
Fig
.
5
.

1
.
Heater
valves
2
.
ABS
pedal
travel
sensor3
.
ABS
pump

Fig
.
10
.
Left
rear
of
engine
compartment
.

4
.
Main
engineharness
con-
nector
5
.
Power
distribution
box

ELECTRICAL
COMPONENT
LOCATIONS
610-5

0013202
0013226

Fig
.
11
.
M42
engine
idie
speed
control
valve
(arrow)
beneath
intake
manifold

0012421

Fig
.
12
.
M44
engine
intake
air
temperature
(¡Al)
sensor
in
air
filter
housing

Fig
.
13
.
M50/S50U
S
engine
intake
air
temperature
(IAT)
sensor
(1)
and
throttle
position
sensor
(2)
.

301180

0012724

Fig
.
14
.
M52/S52U
S
engine
intake
air
temperature
(IAT)
sensor
in
bot-
tom
of
intake
manifold
(throttle
housing
shown
removed)
.

COMPONENT
LOCATIONS