1993 BMW M3 engine overheat

170-
4



RADIATOR
AND
COOLING
SYSTEM
A
quick
testat
the
coolant
temperature
gauge
sender
can



The
auxiliary
cooling
fan
comes
on
when
coolant
tempera

determine
if
the
gauge
is
functioning
correctly
.



ture
exceeds
a
predetermined
leve¡
or
whenever
the
air
condi-

tioning
is
on
.
A
dual-range
temperature
switch
for
cooling
fan
lf
the
gauge
needie
remains
at
the
rest
position
with
theen-



control
is
mounted
on
the
right
side
of
the
radiator
.
See
Fig
.
3
.
gine
warm,
remove
the
harness
connector
from
the
sender
and
jumper
the
correct
terminals
in
the
connector
to
simulate
a
high
engine
temperature
.
See
Table
a
.
Turn
the
ignition
on
.

If
the
gauge
needle
moves
upward,
the
sender
is
faulty
.
If
the

gauge
does
not
respond,
the
wiring
to
the
gauge
is
broken
(open
circuit)
or
the
gauge
itselfis
faulty
.

WARNING
-

1996
and
laten
models
are
OBD
11
compliant
.
Dis-
connecting
electrical
connectors
wíth
the
ignition
turned
on
may
set
fault
codes
in
the
ECM
.
It
is
rec-
ommended
that
you
leave
the
diagnosis
of
faults
in
the
coolant
temperature
sensorsystem
to
the
BMW
dealer
service
department
which
has
specialized
OBD
11
scan
tool
equipment
.

If
the
gauge
needle
reads
too
high
when
the
engine
is
cold,
remove
the
harness
connector
from
the
sender
.
Turn
the
igni-

tion
on
.
lf
the
gauge
needle
position
does
not
change,
the
wir-

ing
or
the
gauge
is
shorted
to
ground
.
If
the
gauge
needle

drops,
the
sender
is
faulty
and
should
be
replaced
.
When
re-

placing
a
faulty
coolant
temperature
sender,
the
gasket
ring
on
the
sender
should
also
be
replaced
.

Tightening
Torque

"
Temperature
gauge
sender
to
engine
18
Nm
(13
ft-Ib)

Cooling
fan,
testing

NOTE-

OnM44
engines
with
manual
transmission,
the
primary
electric
cooling
fan
is
mounted
on
the
engine
side
of
the
radiator
and
is
controlled
by
the
engine
control
module
(ECM)
.
Troubleshooting
thiscircuit
should
be
left
to
an
authorized
BMW
dealer
with
the
proper
diagnostic
equipment

An
otherwise
sound
cooling
system
may
still
overheat,
par-
ticularly
with
prolonged
idling,
due
to
a
failure
of
the
coolíng

fan(s)
.

The
belt-driven
cooling
fan
is
controlled
by
a
temperature
dependent
viscous
clutch
.
A
failed
fan
clutch
may
affect
air
flow
through
the
radiator
resulting
in
overheating
orpossibly
overcooling
.
Speed

Low
sp
High
s

With
the
engine
off,
check
thefan
clutch
by
spinning
thefan
.



eed
The
fan
should
spin
on
the
clutch
with
some
resistance
.



peed
Check
for
signs
of
leaking
fluid
from
the
clutch
.
If
thefan
free-
wheels
with
no
resistance,
cannot
be
tu
rned
by
hand,
or
there
are
signs
of
oil
leakage,
the
clutch
should
be
replaced
.

TROUBLESHOOTING

Fig
.
3
.



Radiatorcooling
fan
temperature
switch
(arrow)
.

WARNING
-

"
Use
caution
when
testing
the
electric
cooling
fan(s)
and
coolant
temperature
switch
.
Keep
hands
and
wires
clear
of
thefan
blades
.
The
cool-
ing
fan(s)
can
run
any
time
the
ignition
is
ON
.

"
For
greatest
safety,
coolíng
fan
and
coolant
tem-perature
switch
tests
shouldbe
performed
on
acoldengine
with
the
air
conditioning
off
.

Table
b
.
Auxiliary
Cooling
Fan
Switching

Temperatures

Switching
temperature
196°F(91°C)
210°F(99°C)

0012506

If
a
faulty
thermostat,
trapped
air,
or
a
restriction
in
the
sys-
tem
is
not
allowing
the
coolant
to
circulate
through
the
radia-
tor,
the
temperature
switch
will
not
close
and
the
auxiliary
cooling
fan
will
not
run
.
Before
making
the
tests
described
be-
low,
make
sure
the
thermostat
is
operating
correctly
as
de-
scribed
earlier
.
The
normal
switching
temperatures
for
the

dual
-speed
switch
are
listed
in
Table
b
.

WARNING

Your
common
sense,
good
judge-
ment,
and
general
alertness
are
cru-
cial
tosafe
and
successful
service
work
.
Before
attempting
any
work
on
your
BMW,
read
the
warnings
and
cautions
on
page
vi¡
and
the
copyright

page
at
the
frontof
the
manual
.
Review
these
warnings
and
cautions
each
time
you
prepare
to
work
on
your
BMW
.
Please
also
read
any
warnings
and
cautions
that
accom-
pany
the
procedures
in
the
manual
.

Fuel
pressure
regulator
See
Fuel
injection
Fue]
pump
general
information
160-1
electrical
tests
160-7
power
consumption,
testing
160-7
delivery
tests160-8
delivery
volume,
testing
g
160-9
electrical
circuit,
checking
160-7
fuse
and
relay
160-6
level
sender
See
pump/fuel
leve¡
sender
operating
fuel
pump
for
tests
160-6
pump/fuel
level
sender
(left
side),
removing/installing
160-6
pump/fuel
leve¡
sender
(right
side),
removing/installing
160-5
relieving
fuel
pressure
and
connecting
fue¡
pressure
gauge
160-8
Fueltank
and
lines
general
information
160-1
draining
160-2
evaporative
control
system
160-4
leve¡
senders,
testing
160-5
removing/installing
160-3
Fundamentals
for
the
do-it-yourself
owner
general
information
010-1
advice
for
the
beginner
010-4
cleanliness
010-4
electrical
testing
010-6
gaskets
and
seals
010-5
non-reusable
fasteners
010-5
planning
ahead
010-4
tightening
fasteners
010-5
wire
repairs
010-6
buying
parts
010-6
genuine
BMW
parts
010-6
information
you
need
to
know
010-7
non-returnable
parts
010-7
emergencies
010-11brake
fluid
leve¡
010-13
car
will
not
start
010-11
changinga
tire
010-11
check
enginewarning
light
010-13
dim
Iights
010-13
jump
starting
car
010-12
low
o]I
pressure
010-13
overheating
010-12

Emergencies
(cont
.)
spare
parts
kit
010-14
towing
010-13
gettingstarted
010-2
lifting
thecar
010-3
raising
car
safely
010-3
safety
010-2
working
under
car
safely
010-4
how
to
use
this
manual
010-2
warnings,
cautions
and
notes
010-2
service
010-7
tools
010-7
basic
tool
requirements010-8
BMW
specialtools
010-11
feeler
gauges
010-10
jack
stands
010-9
oil
change
equipment
010-9
torque
wrench
010-10
volt-ohm
meter
(VOM)
or
Multi-
meter010-10
Fuses
See
Electrical
component
locations

G

Gaskets
See
Fundamentals
for
the
do-it-
yourself
owner
Gearshift
See
Gearshift
linkage
Gearshift
linkagegeneral
information
250-1
automatic
shiftlock,
checking
function
250-5
automatic
transmission
gearshift
250-
3
gear
position/neutral
safety
switch,
replacing
(automatic
transmission)
250-4
gearshift
lever,
installing
(manual
transmission)
250-2
gearshift
lever,
removing
(manual
transmission)
250-1
gearshift
mechanism,
adjusting
(automatictransmission)
250-3
manual
transmission
gearshift
250-1
shift
interlock,
checking
function
(automatic
transmission)
250-6Glass
See
Door
windows
Glove
compartment
See
Interior
trim
Grille
See
Exterior
trim,
bumpers
Guibo
(flex
disc)
See
Driveshaft

Handle,
door
See
Doors
Hardtop
See
Body-general
Headlight
See
Exterior
lighting
Headlight
switch
See
Switches
and
electrical
accessoriesHeater
box
See
Heating
Heater
core

See
Heating
Heater
valve
See
Heating
Heating
general
information
640-1
air
distribution
motors
640-9
air
distribution
motor,
replacing
(rotary
knob)
640-10
blower
motor,
removing/installing
640-1blower
motor
resistor
pack,
replacing
640-3
control
head
640-7
removing/installing
(digital-display)
640-8
removing/installing
(rotary
knob)
640-7
control
module
removing/installing
(digital-display)
640-8
removing/installing
(rotary
knob)
640-8
heater
box,
removing640-4
heater
core,
replacing
640-6
heater
core
temperature
sensor,
replacing
640-7
heater
valve,
replacing
640-3
rear
window
blower
(convertible
models)
640-10
reas
window
defogger
640-10sensor
fan
forinterior
temperature,
replacing
640-9warnings
and
cautions
640-11
Hood
See
Fenders,
engine
hood

Idle
speed
See
Maintenance
program
Idle
speed
control
valve
See
Fuel
injection
Ignition
switch
See
Switches
and
electrical
accessories

INDEX
5