Temperature BMW 540i 1998 E39 Repair Manual

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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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Fuel Tank and Fuel Pump
Evaporative system troubleshooting
- Start by accessing diagnostic trouble codes (DTCs) using a
BMW or BMW compatible aftermarket scan tool.
For purposes of OBD
II emissions compliance, the DME
system sets a diagnostic trouble code (DTC) when it de-
tects a leak that is equal or larger than minimum
lealc
sensed by system.
Malfunction Indicator Light (MIL) is illuminated upon sec-
ond recurrence of fault. See OBD On-Board Diagnostics.
- When leak testing, observe following conditions to obtain
plausible results:
Fuel tank
'1, to 'I., full.
0 Vehicle parked for at least 2 hours to allow fuel to reach
room temperature.
Ideal fuel temperature is 10"- 20°C
(50"
- 68" F).
Do not refuel immediately before
lealc test.
- If a leak is detected, check the following areas:
* Fuel filter cap (leaking or off).
Fuel tank ventilation lines leaking at fuel
tank or activated
carbon canister.
i
Tank ventilation valve leaking (in engine compartment).
Fuel level
sensorlfuel pump cap leaking.
Evaporative system component replacement is covered later
in
th~s group in Fuel Tank and Fuel Lines.

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Fuel Tank and Fuel Pump 1
Activated carbon canister I fuel tank leak
detection unit
(LDP or DMTL), removing . . -
and installing
- Raise rear end of car and support safely.
CAUTION-
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose.
A floor jack is not adequate support.
- Remove left rear wheel and inner fender panel
Remove carbon canisterlfuel tank leak detection unit
(V-8 model shown):
Disconnect electrical harness connector
(A) from fuel tank
leak detection unit.
Pinch and remove quick-disconnect fittings at intake line to
air filter housing
(5) and hose to expansion tank (C).
* Remove mounting clamp and lower canister with fuel tank
leak detection unit.
Installation is reverse of removal.
Tightening
torques
Hose clamp 8 - 13 mm dia. 2 Nrn (18 in-lb)
Hose clamp
13 - 16 rnm dia 3 Nm (27 in-lb)
Running losses (312-way) valve,
removing and installing
The running losses (312-way) valve is located under the car
beneath the driver's seat, just ahead of the fuel filter. A protec-
tive covershieldsfuel system components from road hazards
and dirt.
The engine control module
(ECM) controls the operation of
the 312-way valve (pulse-width modulated). On engine start
up, the valve solenoid is energized for 20 seconds in order to
supply full fuel volume to the fuel rail.
After20 seconds, the
solenoid is deactivated and sprung closed (the bypass is
opened). This reduces the amount of fuel circulating through
the fuel rail and diverts the excess to return to the fuel tank
through the fuel pressure regulator.
The fuel injectors are supplied with pressurized fuel, but ex-
cess fuel is diverted to the fuel tank without first passing
through the fuel rail. This prevents the excess fuel from ab-
sorbing heat in the engine compartment, thus lowering the
temperature and amount of vaporization in the fuel tank.

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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.

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170-5
Radiator and Cooling System
Fan switch calibration (M52, M62 engine)
coniprairoi OUt rlgnal
Auto. ciimilte ~ontioi inpuls via CAN bus
Electric fan activation:
Low speed
91°C (196°F)
High speed 104' C (21 9' F)
< In models manufactured after 911998 (M52 TU engine, M54
engine.
M62 TU engine), the electric cooling fan is controlled
by the engine control module (ECM) via the output final
stage.
The output final stage is mounted on the fan housing, next to
the fan motor. The fan is operated using a pulse width modu-
lated signal. Fan circuit wiring is protected by a 50-amp fuse.
Electric fan activation is based on the following inputs to the
ECM:
Radiator outlet temperature
Calculated catalytic converter temperature
Vehicle speed
* Battery voltage
Calculated
A/C pressure
When the vehicle is first started, the ECM activates the elec-
tric fan briefly at 20% of its maximum speed, then switches
off. This is for diagnostic monitoring. The voltage generated
by the fan when it slows down (acting as a generator) must
match the stored rpm values in the fan output stage toconfirm
that the fan is operating correctly.
NOTE-
If the ECM fault memory indicates a cooling fan fault, check
that the fan is not seized and that it spins freely.
When
A/C is switched ON, the electric fan is not immedi-
ately turned on.
After the engine is switched
OFF the fan may continue to
run at varying speeds for up to 10 minutes, based on cal-
culated catalyst temperature.
Transmission fluid heat exchanger
Automatic transmission fluid lines circulate transmission fluid
(ATF) to and from a heat exchanger at the radiator.
All 6-cylinder
models andV-8 models produced to 911998 are
equipped with a transmission cooler located in a cooling cas-
sette in front of the radiator.

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.. - -
I Radiator and Cooling System
I I 4 The cooling cassette incorporates cooling coils for various
vehicle systems:
1. Steering fluid cooler
2. Transmission oil
coolel
3. AIC condenser
4 In V-8 cars produced after 911998 (M62 TU engine), the en-
gine radiator is divided into an upper chamber (about 80%)
and a lower chamber (about 20%). The ATF heat exchanger
is coupled to the lower chamber.
On cold engine start-up, the engine coolant is heated more
quicltly than the transmission fluid. Heat from engine coolant
is used to warm up the ATF faster, reducing drag in the trans-
mission and improving fuel mileage.
Once the ATF has reached normal operating temperature,
the ATF heat exchanger acts as cooling device. The lower
20% of the radiator
stays cooler than the upper chamber, so
the ATF is cooled more effectively.
4 M62 TU cooling system ducting at radiator:
1. Coolant distribution housing connection
2. Thermostat connection
3. Water cooled alternator connections
4. Transmission fluid heat exchanger connections

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Warnings and cautions
Obse~e the following warnings and cautions when worlting
on the cooling system.
WARNING -
. At normal operating temperature the cooling system is
pressurized. Allow the system to cool as long as possible
before opening (a minimum of one hour), then release the
cap slowly to allow safe release ofpressure.
a Releasing the coolant system pressure lowers the cool-
ant boilingpoint and the coolant may boil suddenly. Use
1 heavy and wear eye and face protection to
guard against scalding.
Use extreme care when draining and disposing of en-
gine coolant. Coolant is poisonous and lethal to hu-
mans andpets. Pets are attracted to coolant because
of its sweet smell and taste. Seek medical attention im-
mediately if coolant is ingested.
CAUTIOG
Avoid adding cold water to the coolant while the engine is
hot or overheated. If it is necessary to add coolant to a
hol
system, do so only with the engine running and coolanl
pump turning.
To avoid excess silicate gel precipitation in the cooling
system and loss of cooling capacity, use BMW coolant
or equivalent low silicate antifreeze.
a If oil enters the cooling system, the radiator, expansion
tank and heating circuit must be flushed with cleaning
agent. BMW recommends removal of the radiator and
expansion
tank to flush.
When
worlcing on the cooling system, cover the alter-
nator to protect it against coolant drips.
Prior to disconnecting the battery, read the battery dis-
connection cautions given in
001 General Warnings
and Cautions.
Begin the diagnosis of cooling system problems with a thor-
ough visual inspection.
If no visual faults are found, it is rec-
ommend that the engine control module (ECM) fault memory
be checked for stored diagnostic trouble codes
(DTCs) using
BMW scan tool
DlSplus or equivalent.

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170-8
I Radiator and Cooling System
Common cooling system faults can be grouped into one of 4
categories:
Cooling system
lealts
Poor coolant circulation
Radiator cooling fan faults
Electrical/electronic faults
Cooling system inspection
- Check that coolant pump drive belt tensioner is functioning
properly and that belt tension is correct. Belt tensioner sys-
tems for the different models are shown in
020 Maintenance.
- Check condition of coolant pump drive belt.
- Checlc coolant hoses for cracks or softness. Checlc clamps
for looseness. Check coolant level and check for evidence of
coolant
lealts from engine.
- Check that radiator fins are not blocked with dirt or debris.
Clean radiator using low-pressure water or compressed air.
Blow outward, from engine side out.
- To check coolant pump:
Remove mechanical cooling fan. See Mechanical
(vis.
cous clutch) cooling fan, removing and installing.
Remove drive belt from coolant pump pulley. See
020
Maintenance.
Firmly grasp opposite sides of pulley and check for play in
all directions.
Spin pulley and check that shaft runs smoothly without
play.
NOTE-
The coolant provides lubrication for the pump shaft, so an oc-
casional drop of coolant
lealing from the pump is acceptable.
If coolant drips steadily from the vent hole, replace the pump.
- At normal engine operating temperature, cooling system is
pressurized. This raises boiling point of coolant.
Leaks may
prevent system from becoming pressurized. If visual evi-
dence is inconclusive, pressure test cooling system as de-
scribed later to help pinpoint hard-to-find leaks.
- If cooling system is full of coolant and holds pressure:
- Use an appropriate scan tool to interrogate engine control
module (ECM) for radiator fan or DME control circuit faults.
Checlc for loose or worn drive belt.
0 Test for failed thermostat or coolant pump impeller. Some
pumps may be fitted with plastic impellers.

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Radiator and Cooling System
Check for cloggedlplugged radiator or coolant passages.
Cooling system pressure test
A cooling system pressure tester is used to test for coolant
leaks, including internal ones. Common sources of internal
coolant leaks are a faulty cylinder head gasket, a
craclted cyl-
inder head, or a cracked engine block.
WARNING-
At normal operating temperature the cooling system is pres-
surized. Allow the system to cool before opening. Release
the cap slowly to allow safe release ofpressure.
4 With engine cold, install pressure tester (BMW special tools
17 0 002117 0 005 or equivalent) to expansion tank. Pressur-
ize system to specification listed in Table a. Cooling system
test pressures.
Pressure should not drop more than 0.1 bar (1.45 psi) for
at least two minutes.
. If pressure drops rapidly and there is no sign of external
leakage, cylinder head gasket may be faulty. Perform com-
pression and leak-down tests.
Test expansion
tank cap using pressure tester with correct
adapter (BMW special tool 17
0 007 or equivalent). Re-
place faulty cap or cap gasket.
Table a. Cooling system test pressures
0021663 I Component l~est pressure
Radiator
11.5 bar (21.75 psi)
Radiator cap
12 bar (29 psi)
CAUTION-
Exceeding the specified test pressure could damage the ra-
diator or other svstem
com~onents.

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170-1 0
I Radiator and Cooling System
Combustion chamber leak test
- If you suspect that combustion chamber pressure is leaking
into the cooling system past the cylinder head gasket, use an
exhaust gas analyzer to test the vapors rising from the cool-
ant at the expansion tank.
CAUTIO&
Use an extension tube above the reservoir neclc to main-
tain distance between the top of the coolant and the gas
analyzer
nozzle. The gas analyzer is easily damaged if it is
allowed to inhale liquid coolant.
* While running engine to checlc for causes of overheat-
ing, observe coolant temperature carefully in order to
avoid engine damage.
Thermostat
If the engine overheats or runs too cool and no other cooling
system tests indicate trouble, the thermostat may be faulty.
In
V-8 models and 6-cvlinder models nroduced afler 911 998
(M52TU or M54 eng'ne), rheelecrricaily heated rhermostal IS
mon tored by [he OBD II diagnostlc software The fault may ic
in the DME software or hardware, or it may lie in the wiring to
the thermostat. See
OED On-Board Diagnostics.
Coolant, draining and filling
(6-cylinder models)
WARNING -
Allow the cooling system to cool before opening or draining
the cooling system.
- Raise front of car and support safely.
WARNING -
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose. A floor jack is not adequate support.
- Remove splash shield from under engine.
4 Loosen radiator bleed screw at top radiator fitting (arrow).
- Remove cap from radiator expansion tank. Set temperature
controls to
full warm.
gallon pail underneath radiator.