1997 BMW 525i cool

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Fuel Injection I
Engine coolant temperature (ECT) sensor,
testing
The ECT sensor is located on the front of the engine in the
coolant~thermostat flange. The ECT sensor is a dual temper-
ature sensor. One circuit provides coolant temperature infor-
mation to the ECM while the other circuit provides coolant
temperature information to the instrument cluster.
The ECM determines the correct ignition timing and
airlfuel
mixture required for the engine by monitoring an applied volt-
age
(5 vdc) to the sensor. Thevoltage drop across the sensor
varies as the coolant temperature (sensor resistance) chang-
es.
NOTE-
The ECT sensor is an NTC (negative temperature coeffi-
cient) type sensor. In other words, as the temperature rises,
resistance through the sensor decreases.
If the ETC sensor input is faulty or non-plausible, the MIL is il-
luminated when OBD
II fault criteria are exceeded. The ECM
assumes a substitute value
(80" C/ 176°F) to maintain engine
operation. The ignition timing is set to a
conse~ativelsafe ba-
sic setting.
Disconnect harness from
ECTsensor (A) at coolant flange at
front of engine.
- Check ECT sensor resistance using a multimeter at sensor
terminals
3 and 4. Peel back protective boot (B) to ID termi-
nal numbers on connector housing.
I ECT sensor resistance @ 20" C (68°F) I 2.2 - 2.7 lkCi
Engine coolant temperature (ECT) sensor,
replacing
I WARNING-
/ Due to risk ofpersonal injury, be sure the engine is cold be- I
I fore replacin~~~~sensor. -
-
I
- Disconnect ECT sensor harness.
- Unscrew ECT sensor from cylinder head and install new sen-
sor.
Use new copper sealing washers when installing sensor.
Replace any lost coolant.
Tightening torque
ECT sensor to coolant flange 13 Nm (10 it-lb)

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I Fuel Injection
Connector X60003 (continued) Electric throttle actuator
25
- 27 28
29
30
31
32
33
I I I
36 jlnput I Knoclc sensor 2, signal 1 Knock sensor
I I I
Input
26
Output
Output
input
Output
Input
I ' I . I
43 1 ln~ut I Electric throttle actuator, signal (Electric throttle actuator
Ground, electric throttle actuator
1 Not
used
Hot film mass air flow sensor
34
- 37
38
39
40
41
42
injection signal
Injection
signal
VANOS valve, signal
Not used
Thermostat characteristic map, signal
Crankshaft position sensor, signal
Not used
35 l~round I~nock sensor, shield 1 ~nock sensor
Cylinder
8 fuel injection valve
Cylinder
5 fuel injection valve
VANOS valve, cylinders
1-4
Characteristic map
Crankshaft positionlrpm sensor
input
input
Ground
Input
Output
Output
Innut
Hot film mass air flow sensor, signal
I
44
45 46
47
48
49
50
51
52
Connector )(GO004
Knock sensor 4, signal
Knock sensor, shield
Oil
level (thermal)
Injection, signal
Injection, signal
Electric throttle actuator, signal
Not used
Ground
Crankshaft position sensor, signal
Not used
Knoclc sensor, shield
Knock sensor
1, signal
Knock sensor
3, signal
Knock sensor, shield
Secondary air injection pump valve, signal
'
Ground
Input
Ground
input Input
Ground
Input
I' I ... I . ~
Knock sensor
Knocic sensor
Oil level sensor
Cylinder
4 fuel injection valve
Cylinder
1 fuel injection valve
Electric throttle actuator
Crankshaft sensor shield
Crankshaft
positionlrprn sensor
Knock sensor
Knock sensor
Knock sensor
Knock sensor
Secondary air injection pump valve
Notes
Instrument cluster
Integrated instrument cluster control
Secondary air injection pump
relay
Pin
1
2
3
Electric (auxiliary) cooling fan 4
Type
Output
Output
Outout
Descriptionlsignal type
Charge indicator signal (terminal
61)
Voltage signal, terminal 30h
Secondam air pump relay, activation
Input
5
Signal, electric (auxiliary) cooling fan, signal
I~ot used

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Fuel Injection I
Connector X60004 (continued)
8 10
11
12
13
14
15
16
9
Output 0
Input
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
39
llnput lsignal l~oolant outlet temperature sensor
Output
Output
Ground
Input
Output
I I - I
40 /output Istart signal Istarter relay
Pedal position sensor (PWG), signal
Output Input
Output
input
Input
Input
Input
Input
Input
input
Input
Output
Input/-output
Input/-output
37
Connector X60003
Pedal position sensor
Fuel pump relay, activation
Oil pressure indicator Pedal position sensor (PWG), ground
Pedal position sensor (PWG), signal
Pedal position sensor (PWG), power supply
Not used
Not used Fuel
pump relay
Instrument cluster
Pedal position sensor
Pedal position sensor
Pedal position sensor
Engine speed signal output (TD)
Not used
Signal
back-up light
DM-TL (diagnostic module,
tank leakage)
Signal oil level sensor
Right rear wheel speed, signal
Clutch pedal position switch, signal
Brake light switch, signal
Not used
Voltage supply, terminal
15
Data link, MFL (multi-function steering wheel)
Brake light test signal
AJC compressor signal
DM-TL (diagnostic module, tank
leakage)
Not used
Diagnosis signal
TxD
Communication link (EWS)
Not used
Not used
CAN-BUS hiqh
38 1 Ground l~round I Coolant outlet temperature sensor
OED II plug
Integrated instrument cluster control module (IKE)
Light module
ABSIDSC control module
Clutch pedal position switch
Brake light switch
Fuse
F14
Airbag contact coil spring
Brake light switch
Heating and
A/C control module
OBD
II plug
Electronic immobilizer (EWS)
CAN-Bus link
CAN-Bus link
Input/-output CAN-Bus low

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--
I Fuel Tank and Fuel Pump
The plastic fuel tank is mounted underneath the center of the
car (underneath the rear seat). Mounted in the fuel tank are
the fuel pump and fuel level sending units. Connecting lines
for the evaporative emission control system and expansion
tank are also attached to the tank.
Fuel
tank capacity for E39 models
Tank capacity
70 liters (18.5 gal)
Reserve capacity
8 liters (2.1 gal)
Fuel tank, draining
Drain fuel tank into a safe storage unit using an approved fuel
pumping device.
WARNING-
# Before removing tank, be sure that all hot components,
such as the exhaust system, are completely cooled down.
Fuel may be spilled. Do not smoke or
work near heat-
ers or other fire hazards.
- Start engine and allow to run 10 - 15 seconds to fill fuel com-
pensating siphon assembly. This will allow both lobes of fuel
tank to he drawn off through fuel filler pipe,
- Disconnect negative cable from battery.
CAUTION-
Prior to disconnecting the batteg read the battery discon-
nection cautions given
in 001 General Warnings and Cau-
tions.
- Remove fuel tank filler cap
- Slide suction hose into filler neck about 130 cm (51 in.), twist-
ing as necessary. Withdraw fuel into storage unit.
- Monitor fuel level reduction in both lobes:
- Remove rear seat cushion and access both fuel tank send-
er harness connectors.
Use multimeter to measure resistance at both senders,
Resistance should drop as fuel level drops.
- If siphoning mechanism is faulty, drain left tank lobe sepa-
rately by removing sender cover and pumping fuel directly
out of left lobe.

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176 Radiator and Cooling System
General ........................... .I7 0.2
Special tools
........................ .I7 0.2
Cooling system overview
(M52 TU shown. others similar) ......... .I7 0.3
Coolant pump
....................... .I7 0.3
Thermostat
......................... .I7 0.3
Mechanical thermostat (M52 engine)
..... .I7 0.4
Electrically heated thermostat
.......... .I7 0.4
Radiator and expansion tank
........... .I7 0.4
Mechanical cooling fan with viscous clutch
.I7 0.4
Electric (auxiliary) cooling fan ........... .I7 0.4
Transmission fluid heat exchanger
....... .I7 0.5
Warnings and cautions
................ .I7 0.7
Troubleshooting ................... .I7 0.7
Cooling system inspection
............. .I7 0.8
Cooling system pressure test
........... .I7 0.9
Combustion chamber leak test
......... .I7 0.10
Thermostat
........................ .I7 0.1 0
Cooling System Service ........... 170-10
Coolant. draining and filling
(6-cylinder models)
.................. 170-1 0
Coolant. draining and filling (V-8 models)
. 170-12
Cooling system. bleeding
............. 170-14
Mechanical (viscous clutch) cooling fan.
removing and installing
............... 170-14
Electric cooling fan.
removing and installing
............... 170-15
Thermostat. removing and installing
(M52engine) ....................... 170-16
Thermostat. removing and installing
(M52 TU or M54 engine) .............. 170-17
Thermostat. removing and installing (V-8 models)
....................... 170-1 8
Coolant pump. replacing (6-cylinder models)
.................. 170-1 9
Coolant pump. replacing (V-8 models) ... 170-20
Radiator. removing and installing
....... 170-22
Expansion tank. removing and
installing . . 170-24

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I Radiator and Cooling System
This section covers component repair information for the en-
gine cooling system.
Heater core replacement is covered in
640 Heating and Air
Conditioning.
Special tools
Special tools are necessaryfor belt-driven fan clutch removal
and also for pressure testing the cooling system.
4 Cooling fan counterhold wrench
(Tool No. BMW
11 5 030)
4 Cooling fan wrench
(Tool No. BMW
11 5 040)
< Expansion tank cap test adaptor
(Tool No.
BMW 17 0 007)
17 0 002 4 Cooling system pressure tester set
1 17 o 005 (Tool No. BMW 17 0 OOZi17 0 005)

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- -
L- -
--
-. - - - Radiator and Cooling sYstelll/ --
Cooling system overview
(M52 TU shown, others similar)
Coolant pump
A centrifugal coolant pump is mounted to the front of the en-
gine. The belt-driven pump circulates coolant through the
system whenever the engine is running.
Thermostat
Two types of thermostats are used in the cars covered by this
manual. 6-cylinder models built up to
911 998 (M52 engine)
use a conventional mechanical thermostat. All
V-8 models
and 6-cylinder models from
911998 use an electrically heated
thermostat.

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-
I Radiator and Cooling System
Mechanical thermostat
(M52 engine)
4 The mechanical thermostat relies on coolant temperature to
operate. While coolant is cold, it remains closed, and circu-
lating coolant bypasses the radiator for rapid engine warm
up. At higher coolant temperature, the thermostat progres-
sively opens to allow coolant flow through the radiator, thus
controlling engine temperature. Port
A restricts coolant flow
from radiator, and port
B restricts coolant flow to radiator.
Electrically heated thermostat
4 The electrically heated thermostat is DME map-controlled.
The engine control module (ECM) activates the thermostat to
maintain engine coolant temperature within a narrow range.
In case of failure of the electronics, the mechanical function of
the thermostat acts as a fail-safe.
Radiator and expansion tank
The radiator is a crossflow design. An expansion tank pro-
vides for coolant expansion at higher temperatures and easy
monitoring of the coolant level.
On cars with automatic transmission, ATF is circulated
through an additional heat exchanger (ATF cooler).
Mechanical cooling fan with viscous clutch
The mechanical cooling fan is belt-driven via a viscous fluid
coupling (clutch) attached to the front of the coolant pump.
The fan clutch controls the speed of the fan based on the tem-
perature of the air flowing through the radiator core.
Electric (auxiliary) cooling fan
The electric cooling fan is mounted on the bumper side of the
radiator.
In models manufactured up to
911 998 (M52 or 1997 M62 en-
gine), the electric cooling fan is controlled by a dual tempera-
ture fan switch mounted in the side of the radiator.