BMW 540i 1999 E39 Workshop Manual

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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.

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170-1 1
Radiator and Cooling system/
4 Remove drain plug (arrow) at bottom of radiator.
Coolant is poisonous. It is especially lethal to pets. Clean up
spills immediately and rinse the area with
wate,: If coolant is
- Place a 3-gallon pail beneath the engine block. Remove en-
gine block coolant drain plug and drain coolant.
< M52 TU 1 M54 engine: Bloclc drain plug is located on exhaust
side of engine block at cylinder
2 (arrow).
M52 engine:
Bloclc drain plug is located on exhaust side of
engine
bloclc between cylinders 3 and 4.
- Reinstall radiator and engine block drain plugs using new
sealing washers.
- Before refilling radiator:
Switch ignition to
ON. (Do not start engine).
Set temperature controls to full warm.
Set blower control to low.
- Using a coolant mixture of 50% antifreeze and 50% distilled
water, fill expansion tank slowly. Continue until coolant
emerges from bleed screw. Cooling system capacity is listed
in Table c. Cooling system capacity (6-cylinder models).
NOTE-
Be sure radiator bleed screw is loose when filling cooling
system.
Tap water may cause corrosion of radiator, engine and
coolant hoses.
Coolant can be reusedprovided it is clean and less than
two years old. Do not reuse coolant when replacing dam-
aged engine parts.
- Bleed cooling system. See Cooling system, bleeding
Table c. Cooling system capacity (6-cylinder models)
Engine Capacity
M52, M52TU, M54
10.5 liters (1 1.1 US qls)

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170-1 2
I Radiator and Cooling System
Tightening torques
Block drain plug to
block 25 Nm (1 8 ft-ib)
Radiator drain plug to radiator
2-3 Nm (18-27 in-lb)
Coolant, draining and filling (V-8 models)
WARNING -
Allow the cooling system to cool before opening or draining
the cooling system.
- Raise front of car and support safely.
I WARNING- 1
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
I the purpose. A floorjack is not adequate support 1
- Remove splash shield from under engine.
Loosen radiator bleed screw at top radiator fining (arrow).
Remove cap from radiator expansion tank. With ignition
switch in
ON position, set temperature controls to full warm.
Place 5-gallon pail underneath radiator.
4 Remove drain plug (arrow) on bottom of radiator and allow
coolant to drain.
NOTE-
For radiators without drain plug, remove lower hose to drain
radiator.
WARNING
-
Coolant is poisonous. It is especially lethal to pets. Clean up
spills immediately and rinse the area with water. If coolant is
ingested, immediately seek medical attention.

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170-1 3
Radiator and Cooling ~vsteml
< V-8 engine bloclc drain plugs (one shown at arrow) are locat-
ed on each side of engine block (exhaust manifold removed
for photo).
- Place 5-gallon pail underneath engine block coolant drain
plugs.
- Remove engine bloclc coolant drain plugs and drain coolant.
- Reinstall radiator and engine block drain plugs using new
sealing washers.
- Before refilling radiator:
Switch ignition to
ON. (Do not start engine)
Set temperature controls to full warm.
- Set blower control to low.
- Using a coolant mixture of 50% antifreeze and 50% distilled
water, fill expansion tank slowly. Continue until coolant
emerges from bleed screw. Cooling system capacity is listed
in Tabled. Cooling system capacity
(V-8 models).
NOTE- Be sure radiator bleed screw is loose when filling cooling
system.
Tap water may cause corrosion of radiator, engine and
coolant hoses.
Coolant can often be reused provided it is clean and less
than two years old. Do not reuse coolant when replacing
damaged engine parts.
- Bleed cooling system. See Cooling system, bleeding
Tabled. Cooling system
capacity (V-8 models)
M62, M62 TU 12.0 liters (12.7 US qts)
Tightening torques
Block drain plug
25 Nm (18 ft-lb)
Radiator drain plug
2 - 3 Nm (18 - 27 in-lb)

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Radiator and Cooling System
Cooling system, bleeding
Trapped air in the cooling system can prevent proper coolant
circulation and overheating. Wheneverthe coolant is drained
and filled, bleed the cooling system to remove trapped air.
4 Loosen bleed screw (arrow) on radiator expansion tank.
- Set temperature controls in passenger compartment to full
warm, set blower to low setting and turn ignition to
ON posi-
tion (do not start engine).
CAUTIOIG
On late model cars with latent heat pump, do not turn ignition
to ON position.
- Slowly add coolanUdistilled water mixture to expansion tank
until it spills from bleed screw. When coolant spilling from
bleed screws is free of air bubbles, tighten screw and replace
cap on expansion tank.
Run engine until it reaches operating temperature,
- After engine has cooled, recheck coolant level.
Top up so that coolant level indicator is at MAX.
- If trapped air cannot be bled manually, pressure-bleed sys-
tem using cooling system pressure tester.
CA UTlON--
Always use genuine BMW coolant or its equivalent to avoid
the formation of harmful, clogging deposits
in the cooling sys-
tem.
Tightening torque
Radiator bleed screw to radiator 2.5 Nm (22 in-lb)
Mechanical (viscous clutch) cooling fan,
removing and installing
The procedure given here describes the removal of the me-
chanical fan and fan shroud. It is possible to remove the fan
without the shroud.
< Working at top of fan shroud:
Remove expansion tank bleed screw (arrow) and expan-
sion tank locking tabs.
Push top of expansion
tank toward engine and lift to free
from lower mounts.
- Remove two expansion rivets in upper corners of fan shroud.
Unclip expansion tank bleed hose located under shroud.