1999 BMW 525i Workshop Manual

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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.

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Radiator and Cooling System
Remove rubber trim strip between top of shroud and radiator.
Using 32 mm wrench
(BMW special tool 11 5 040) on fan
clutch nut (arrow), turn wrench in a clockwise direction
(working from front of car) while counterholding pulley with
BMW special tool
11 5 030. Spin fan off coolant pump.
NOTE-
The radiator cooling fan nut (32 mm wrench) has left-hand
threads.
Unclip AUC (air quality) sensor from shroud,
M54 engine: Disconnect auxiliary coolant pump from base of
fan shroud.
Lift fan and shroud together out of engine compartment.
To replace fan clutch, remove fan mounting bolts and sepa-
rate viscous clutch from fan.
Installation is reverse of removal.
Tightening
torques
Clutch nut to pump
Without
BMW tool 11 5 040 40 Nm (29 ft-lb)
With BMW tool 11 5 040 30 Nm
(22 ft-lb)
Fan to viscous clutch 10 Nm (89 in-lb)
Electric cooling fan, removing and
installing
The electric cooling fan is mounted behind the front bumper,
in front of the
A/C condenser.
- Remove front bumper. See 510 Exterior Trim, Bumpers.
- Remove left and right headlights. See 630 Lights,
- Where applicable, detach horizontal air ducts behind front
bumper and fold to side.
- Disconnect fan electrical connector on right side of radiator
shroud and lay aside.
- Detach wire loom from air duct in front of cooling fan
- Pry out expansion rivets holding air duct. Slide air duct down-
ward to remove.

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170-1 6
I Radiator and Cooling System
- Remove fan and fan shroud mounting fasteners. Slide fan
and fan shroud downward to remove.
- Reinstallation is reverse of removal.
Thermostat, removing and installing
(M52 engine)
The coolant thermostat is installed in a housing at the front of
the engine.
- Drain coolant from radiator and engine block. See Coolant,
draining and filling (6-cylinder models).
WARNING -
Allow the cooling system to cool before opening or draining
the system.
- Remove mechanical cooling fan and fan shroud. See Me-
chanical (viscous clutch) cooling fan, removing and in-
stalling.
- Disconnect coolant hoses from thermostat housing.
- Remove thermostat housing from front of engine.
- Remove thermostat. Note thermostat direction and orienta-
tion before removing.
- Installation is reverse of removal, noting the following:
- Use new O-ring and gasket(s) when installing thermostat
and housing.
NOTE-
Some thermostats have a direction arrow or vent hole near
the edge. Install the thermostat so that either the arrow or
hole are at the top.
Fill system with coolant as described in Coolant, draining
and filling (6-cylinder models).
CAUTION-
Be sure to reconnect ground wire@) at thermostat housing
mounting bolt, where applicable.