2001 BMW 525i air flow

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01 0-1 0
General
Electrical testing
Many electrical problems can be understood and solved with
only a little fundamental knowledge of how electrical circuits
function.
Electrical current
only flows in a complete circuit. To operate.
every electrical device in the car requires a complete circuit
including a voltage source and a path to ground. The positive
(+) side of the battery is the original voltage source, and
ground is any return path to the negative
(-) side of the bat-
tery, whether through the wiring harness or the car body. Ex-
cept for portions of the charging system, all electrical current
in the car is direct current (DC) and flows from positive
(+) to
negative
(-).
4 Switches are used to turn components on or off by complet-
ing or interrupting the circuit.
A switch is "open" when the cir-
cuit is interrupted, and "closed" when the circuit is completed.
See
600 Electrical System-General for electrical trouble-
(LW, 1 shooting
Wire repairs
Light bulb
(consumer) ' - Repairs to a wiring harness require special care to make the
repair permanent. The wire ends must be clean.
if frayed or
Car body otherwise damaged, cut off the end and remove enough insu- (ground) i Battery lation to complete the repair. if the wire is too short, splice in a BOZLiEL new piece of wire of the same size and make two connec-
tions.
Use connectors that are designed for the purpose. Crimped
on orsoldered-on connectors are best. Crimp connectors and
special crimping pliers are widely available. If soldering, use
needle nose pliers to hold the wire near the solder joint and
create a "heat dam". This keeps the heat and the solder from
traveling up the wire. Always use a solder made specifically
for electrical
work (rosin core).
NOJE-
Twisting wires together to make a repair is not recommend-
ed. Corrosion and vibration will eventually spoil the connec-
tion and may lead to irreparable damage to sensitive
electronic components.
Insulate the finished connection. Electronics stores can sup-
ply heat-shrinkable insulating tubing that can be placed on to
the wire before connecting, slid over the finished joint, and
shrunic to a tight fit with a heat gun or hair dryer. The next best
alternative is electrical tape. Make sure the wire is clean and
free of
solder flux or other contamination. Wrap the joint tight-
ly to seal out moisture. See
600 Electrical System-General
for more information.

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020-1 4
Maintenance
- When oil flow has diminished to an occasional drip, reinstall
drain plug with a new metal sealing washer and torque plug.
Tightening torque Engine oil drain plug to oil pan
25 Nrn (1.8 ft-lb)
6-cylinder oil filter assembly
r------ 1
< Working at oil filter housing (1):
Lubricate and install new oil filter O-rings (3, 4).
Install a new filter cartridge (5).
lnstall and tighten housing cover (2).
6-cylinder oil filter assembly shown, V-8 is similar.
Tightening torque Cover to oil filter housing
25 Nm (1.8 it-lb)
- Refill crankcase with oil. Approximate oil capacity is listed in
Tabled. Engine oil with filter change. Use dipstick to
check correct oil level.
- Start engine and check that oil pressure warning light
immediately goes out.
- Allow engine to run fora few minutes to circulate new oil, then
check for leaks at drain plug and oil filter. Stop engine and re-
check oil level
The section describes other routine maintenance done in the
engine compartment. Information on engine oil service is
giv-
enkar~ier inthis group.
For these procedures, it is not necessary for the car to be
raised and supported off the ground.
Accelerator and linkage
The accelerator and linkage at the throttle housing should be
lubricated periodically. Use ageneral purposeoil on the joints
and bearings of the linkage. Use a multipurpose grease on
the bearing points of the throttle plate.
Air filter, replacing
The specified replacement intervals forthe air filter are based
on normal use. If the car is operated primarily in dusty
conditions, the air filter should be serviced more frequently.

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Maintenance
< Release mass air flow sensor clips (A).
Release upper air filter housing clips (B).
4 Lift air filter upper housing, and remove filter element.
NOTE-
V-8 engine air filter assembly shown in illustration. 6-cylinder
air filter assembly is similar but located at the left front of the
engine compartment.
- On installation, install O-ring for mass air flow sensor into
retaining clips in air filter upper housing.
- Replace air filter and upper air filter housing, and attach
upper air filter housing clips.
Cooling system, checking
Antifreeze raises the boiling point and lowers the freezing
~oint of the coolant. BMW recommends enaine coolantthat is
a 50 150 mixture of distilled water and ethGene glycol-based
antifreeze.
Routine cooling system maintenance consists of maintaining
the coolant level and inspecting hoses. Because the coolant's
anticorrosion and antifreeze additives gradually lose their ef-
fectiveness, replacement of the coolant every three years is
recommended.
CAUJION-
Use only BMWapprovedphosphate-free antifreeze when
filing the cooling system. Use of antifreeze containing
phosphates is harmful to the cooling system.
4 Float in radiator tank indicates coolant level. Inspect while
coolant is cold.
When upper mark on float is level with top of filler neck,
coolant is at minimum allowable level.
When lower mark on float is level with top of filler neck,
coolant is at maximum level.
Hose connections should be tight and dry. Coolant seepage
nnection indicates either that hose clamp is

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11 0-4
/Engine Removal and Installation
- Disconnect negative (-) cable from battery.
CAUTION- Prior to disconnecting the
batteg read the battery discon-
nection cautions
in 001 General Cautions and Warnings.
- Remove engine hood, or place in service position. See 410
Fenders, Engine Hood.
4 Remove left and right interior ventilation ducts (lefl side
shown):
Release ventilation filter cover latch (A) and remove cover.
Release plastic loclting tab
(6) or release locking tabs on
top of duct (later models).
Rotate duct counterclocltwise to
unloclt from bulkhead and
remove (arrow).
Disconnect electrical harness from hood switch (C).
Release spring
loclt (D).
Slide filter housing away from inner fender to remove.
Removal of right side ventilation duct is similar.
Remove rear bulkhead panel:
Remove rubber sealing gasket (arrow).
- Remove 3 mounting clips (A).
Remove
4 retaining screws (6).
Lift off panel.
Remove complete air filter housing:
Loosen
intalte duct hose clamp (A) at throttle assembly.
Loosen clamp and remove idle control line from intalte duct
(6) and (where applicable) disconnect idle speed control
valve electrical harness connector.
Disconnect harness connector (C) from mass air flow sen-
sor.
Remove air filter housing mounting screw (D).
Disconnect vent tube
(E).
Loosen air intake duct clamp (F).
Carefully lift air filter housing out of engine bay.

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110-15
Engine Removal and lnstallation
- Installation is reverse of removal, noting the following:
Replace all gaskets. O-rings and seals.
Use new fuel injector seals
Check that engine drive belts properly engage pulley
grooves.
Inspect O-ring seal between mass air flow sensor and air
filter housing. To facilitate reassembly, coat seal with acid-
free grease.
Change engine oil and filter and
check all other fluid levels.
See
020 Maintenance.
Refill and bleed cooling system. See
170 Radiator and
Cooling System.
CAUTION--
When reattaching throttle assembly harness connectoc con-
nector is
fuNy tightened when arrows on connector and plug
line up.
Tightening torques
Coolant drain plug to cylinder block
25 Nm (18 ft-lb)
Engine mount to
subframe (M10) 45 Nm (33 ft-ib)
Exhaust manifold to cylinder head
M6 10 Nm (89 in-lb)
M7 or ME 20 Nm (15 ft-lb)
Intake manifold to cylinder head
M7 15 Nm (I 1 ft-lb)
ME 22 Nm (16 ft-lb)
Radiator cooling fan to coolant pump
40 Nm (30 ft-lb)
Radiator drain screw to radiator
2.5 Nm (22 in-lb)

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I Engine Removal and Installation
WARNING -
Use extreme caution when draining and disposing of engine
coolant. Coolant is poisonous andlethal to humans andpets.
Pets are attracted to coolant because of its sweet smell and
taste. Seek medical attention immediately if coolant is ingest-
---
Working at rear of intake manifold:
Disconnect brake booster vacuum line (A).
Disconnect fuel tank vent line
(6).
Disconnect hoses (C and D) at coolant manifold
- Remove transmission harness support (E).
- Remove oil filter housing assembly from fender:
- Remove oil filter housing mounting fasteners.
Use stiff wire to secure oil filter housing to engine.
NOTE-
Do not disconnect oil lines from filter housing.
4 Disconnect supply and return fuel lines (where applicable) at
or near fuel rail. Plug open fuel lines.
NOTE-
BMW uses three styles of fuel line connections; a slngle use
clamp, a locking fitting that uses special tool
16 7 050 to re-
lease, and a
quiclc release sleeve (arrows) that disconnects
the line when depressed.
WARNING-
Fuel In fuel line is under pressure (approx. 3 - 5 bar or45 -
75 psi) and may be expelled. Do not smoke or worlc near
heaters or other fire hazards. Keep a fire extinguisher
handy. Before disconnecting fuel hoses, wrap a cloth
around fuel hoses to absorb any lealcing fuel. Catch and
dispose of escaped fuel. Plug all open fuel lines.
. Always unscrew the fuel tank cap to release pressure
in the tank before worlcing on the tank or lines.
< Remove air filter housing and mass air flow sensor:
Disconnect mass air flow sensor (A) and
intalte air temper-
ature sensor
(6) electrical harness connectors.
. Remove air filter housing mounting fastener (arrow).
Loosen intake hose clamp (C).
M62 engine: Remove hose at idle air stabilizer.
Remove air filter housing with mass air flow sensor.
Remove intalte hose from throttle body.

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11 3-9
Cylinder Head Removal and Installation
< Remove left and right interior ventilation ducts (left shown):
Release ventilation filter cover latch (A) and remove cover.
Release plastic locking tab
(6) or release locking tabs on
top of duct (later models).
Rotate duct counterclockwise to unlock from bulkhead and
remove (arrow).
Disconnect electrical connector from hood switch
(C).
Release spring lock (D).
Slide filter housing away from inner fender to remove.
Removal of right side ventilation duct is similar.
Remove rear bulkhead panel: Remove rubber sealing
gasket (arrow).
0 Remove 3 mounting clips (A).
Remove
4 retaining screws (6).
Lift out panel.
< Remove complete air filter housing:
Loosen
intake duct hose clamp (A) at throttle assembly.
Loosen clamp and remove idle control hose from
~ntake
duct (6) and disconnect Idle speed control valve electr~cal
harness connector.
Disconnect
electr~cal harness connector (C) from mass alr
flow sensor.
Remove air filter housing mounting screw (D).
Disconnect vent tube
(E).
Loosen air intake duct clamp (F).
Carefully lift air filter housing out of engine bay.
4 Remove positive battery cable and intake manifold cover:
Remove protective cover from positive (+)jumper post (A).
Loosen and remove battery lead mounting nut.
Remove battery lead and push down through intake mani-
fold.
Remove trim caps (arrows) from fuel injector cover.
Remove cover hold down fasteners and lift off cover.

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- --
Cylinder Head Removal and Installation 1 --
< Remove complete air filter housing assembly with mass air
flow sensor:
Loosen
intalte duct hose clamp (A) at throttle assembly.
Loosen clamp and remove idle control line from intake duct
(B) and disconnect idle speed control valve electrical har-
ness connector.
Disconnect electrical harness connector
(C) from mass air
flow sensor.
Remove air filter housing mounting screw
(D).
Disconnect vent tube (E).
. Loosen air intalte duct clamp (F).
Carefully lifl air filter housing, mass air flow sensor, and in-
take duct hose out of engine bay.
4 Disconnect positive battery cable and remove intake rnani-
fold cover:
Remove protective cover from positive (+)jumper post.
Loosen and remove battery lead mounting nut (A).
Remove lead and push down through intake manifold.
* Remove trim covers (arrows) from fuel injector cover.
Remove cover hold down fasteners and lifl off cover.
4 Worlting above engine, disconnect the following:
Vent line from cylinder head cover. To remove, pinch clips
(arrows).
Electrical harness connector from VANOS solenoid valve
(A).
- Remove oxygen sensors and exhaust manifolds. See 180
Exhaust System.
CAUTION-
Remove oxygen sensors before removing exhaust mani-
fold to prevent damage.
Label oxygen sensor harness connectors so that they
can be reassembled correctly Do not interchange con-
nectors.
NOTE-
Front exhaust manifold must be removed before rear
manifold.