1998 BMW 540i Ac system

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General
0 GENERAL, MAINTENANCE covers general vehicle infor-
mation
(010 General) as well as the recommended mainte-
nance schedules and service procedures to perform BMW
scheduled maintenance
work (020 Maintenance).
The next seven sections
(1 through 7) are repair based and
organized by three digit repair groups. Most major sections
begin with a GENERAL repair group,
e.g. 100 Engine-Gen-
eral. These "00 (double zero) groups contain descriptive the-
ory of operation and system troubleshooting information. The
remainder of the repair groups within a section contain the
service and repair information. The last two sections contain
detailed electrical wiring schematics and OBD
II scan tool and
diagnostic information.
Warnings, cautions and notes
Throughout this manual are many passages with the head-
ings WARNING, CAUTION, or NOTE. These very important
headings have different meanings.
WARNING-
The text under this heading warns of unsafe practices that
are very
likely to cause injury, either by direct threat to the per-
son(~) performing the work
orby increasedrisl( of accident or
mechanical failure while
drivinq.
CAUTION-
A CAUTION calls attention to importantprecautions to be ob-
senfed during the repair work that will help prevent acciden-
tally damaging the car or its parts.
NOTE-
A NOTE contains helpful information, tips that will help in do-
ing a betterjob and completing it more easily.
Please read every WARNING, CAUTION, AND NOTE in
001
General Warnings and Cautions and as they appear in re-
pair procedures. They are very important. Read them before
you begin any maintenance or repair job.

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.
General
WARNING-
Never run the engine in tile work area unless it is well-ven-
tilated. The exhaust should be vented to the outside. Car-
bon monoxide (CO) in exhaust kills.
Remove all neckties,
scarfs, loose clothing, or jewelry
when working near a running engine or power tools.
Tuck in shirts. Tie long hair and secure it under a cap.
Severe injury can result from these things being
caugiit
in rotating parts.
Remove rings, watches, and bracelets. Aside from the
dangers of moving parts, metallic jewelry conducts
electricity and may cause shorts, sparks, burns, or
damage to the electricalsystem when accidentally con-
tacting the battery or other electrical terminals.
Disconnect the battery negative
(-) cable whenever
working on or near the fuel system or anything that is
electrically powered. Accidental electrical contact may
damage the electrical system or cause a fire.
Fuelis highly flammable. When working around fuel, do
not
smoke or work near heaters or other fire hazards.
Keep an approved fire extinguisher handy.
The fuel system is designed to retain pressure even
when the ignition is off When worlcing with the
fuelsys-
tem, loosen the fuel lines slowly to allow the residual
pressure to dissipate gradually. Take precautions to
avoid spraying fuel.
. Illuminate the worlc area adequately and safely Use a
portable safety light for worlcing inside or under the car.
A fluorescent type
light is best because it gives off less
heat. If using a light with a normal incandescent bulb,
use rough service bulbs to avoid
breakage. The hot fil-
ament of an accidentally broken bulb can ignite spilled
fuel or oil.
Keep sparks, lighted matches, and any open flame
away from the top of the battery. Hydrogen gas
emitted
by the battery is highly flammable. Any nearby source
of ignition may cause the battery to explode.
Never lay
tools or parts in the engine compartment or
on top of the battery. They may
fallinto confinedspaces
and be difficult to retrieve, become caught in belts or
other rotating parts when the engine is started, or
cause electrical shorts and damage to the electrical
system.

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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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General
Torque wrench
A torque wrench is used to precisely tighten threaded fasten-
ers to a predetermined value. Many of the repair procedures
in this manual include BMW-specified torque values
in New-
ton-meters (Nm) and the equivalent values in foot-pounds
(ft-
Ib).
4 Several types of torque wrenches are available. An inexpen-
sive beam-type (top) is adequate but must be read visually. A
ratchet-type (bottom) can be preset to indicate (click) when
the torque value has been reached. They all do the same job,
but offer different convenience features at different prices.
The most convenient ones have a built-in ratchet, and can be
preset to indicate when a specific torque value has been
reached. Follow the wrench manufacturer's directions
for use
to achieve the greatest accuracy.
A torque wrench with a range up to about 150 Nm (1 10 ft-lb) BOIBFNG has adequate capacity for most of the repairs covered in this
manual. For recommended torque values of
10 Nm orbelow,
the English system equivalent is given in inch-pounds (in-lb).
These small values may be most easily reached using a
torque wrench calibrated in inch-pounds. To convert
inch-
pounds to foot-pounds, divide by 12.
Digital multimeter
4 Many of the electrical tests in this manual call for the mea-
surement of resistance (ohms) or voltage values. For safe
and accurate tests of sensitive electronic component and
systems, a multimeter or digital
volt/ohm meter (DVOM) with
high input impedance (at least
10,000Sr) should be used.
Some meters have automotive functions such as dwell and
pulse width that are useful for troubleshooting ignition and
fuel injection problems.
CAUTIOI\C
Vehicle electronic systems may be damaged by the high cur-
rent draw of a test light with a normal incandescent bulb. As
a general rule, use a high impedance digital multimeter or an
LED test light for all electrical testing.

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General
Cars with discharged or dead batteries can be jump-started
using the good battery from another car. See owner's manual
for proper instruction on jump starting. When jump-starling
the engine, always note the following warnings.
4 Lower car. With all wheels on ground, fully tighten nuts in a
WARNING-
* Battery acid (electrolyte) can cause severe burns, and will
damage the
cal; clothing, and you. If electrolyte is spilled,
wash the surface with large quantities of water.
M itgets into
eyes, flush them with water for several minutes and call a
doctor.
B4
5
43
2 BOOIFNG.
Batteries produce explosive and noxious gasses.
Keeps sparks and flames away. Do not smoke near
batteries.
Do notjump-start the engine
ifyou suspect that the bat-
tery is frozen. Trappedgas may explode. Allow the bat-
tery to thaw first.
Do not quick-charge the battery (for boost starting) for
longer than one minute, and do not exceed
16.5 volts
at the battery with the boosting cables attached. Wait at
least one minute before boosting the battery a second
time.
crisscross pattern.
Torque wheel nuts when installing wheel.
Check inflation pressure of spare tire.
Tightening torque
Wheel to wheel hub 120 Nm (89 ft-ib)
Jump starting
Indicator and warning lights
Many vehicle systems are self-monitored for faults while driv-
ing. Generally,
a red warning lamp that comes on during driv-
ing should be considered serious. If you cannot immediately
determine the seriousness of the warning light, stop the vehi-
cle in a safe place and turn the engine off as soon as possible.
Consult the owner's manual for additional information on the
warning lamp and the recommended action.
If the Malfunction Indicator Lamp (MIL)
(Check Engine or Ser-
vice Engine Soon warning light) comes on orflashes, it indi-
cates that an emissions-related fault has occurred. Faults
such as a bad oxygen sensor or a dead fuel injector can
cause the exhaust or evaporative emissions to exceed a
specified limit. When these limits are exceeded, the MIL will
be turned on. The engine can be safety driven with the light
on, although the emission systems should be
checked as
soon as possible. See OBD On-Board Diagnostics for

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01 0-20
General
more information on the Check Engine Light and the on-
board diagnostic system.
Towing
The cars covered by this manual should be towed with a tow
truck using wheel lift or flat bed equipment. Do not tow the car
on all four wheels except
forvery short distances to move it to
a safe place.
CA U JION-
Do not tow with sling-type equipment The front spoilers and
b~m~er covers may sustain damage.
4 To access threaded towing eye socltet, pry open trim on front
or rear bumper.
NOJE-
A towing eye is provided in the luggage compartment tool lcit.
The towing eye can be screwed into the front or rear bumper.
4 Install towing eye into threaded hole.
- Standard transmission: Do not tow with rear wheels on
ground unless absolutely necessary.
- Automatic transmission: Have rear wheels placed on dollies,
or use flat bed truck. Use towing eye for winching vehicle on
flat bed.
CAUTION-
Automatic transmission fluid (ATF) does not circulate when
I the car is towed. Severe transmission damage may result.
NOTE-
Be sure transrnission fluid has been topped off before
starting tow.
Always tow car with transrnission lever in
N (neutral).
. ATF draining and filling is covered in 240 Automatic
Transmission.
Be sure to read the filling and draining pro.
cedure, as special service equipment is required to
checlc
the fluid level.

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Spare parts kit
Carrying a basic set of spare parts can prevent a rninorbreak-
down from turning into a major repair annoyance. The list be-
low is a good place to start.
Spare parts kit
- basic
Polyribbed drive
belt(s)
BMW engine oil: one or two quarts
BMW engine coolant:
1 gallon of premixed 50150 BMW
anti-freeze and water
Fuse assortment:
7.5A. IOA, 1 5A, 20A, 30A. 50A
Radiator hoses: upper and lower
Spare parts
kit - additional contents
Exterior lighting bulbs: headlight, bralte light, turn signal,
and taillight
* Wiper blades or blade inserts
Brake fluid: new, unopened bottle, DOT
4 specification
Main relay for DME system

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020 Maintenance
General ........................... .02 0.2
Special tools ........................ .02 0.2
Service Interval Indicator (Sll) ........... .02 0.3
Service Interval Indicator (Sll), resetting ... .02 0.3
Inspection I, Inspection 11 ............... .02 0.5
Maintenance Tables ................ .02 0.6
Fluid and Lubricant Specifications .. .02 0.9
Fluids and lubricants ................. .02 0.10
Engine Oil Service ................ .02 0.1 I
Engine oil. checking level ............. .02 0.12
Engine oil and filter. changing .......... .02 0-13
Engine Compartment Maintenance . .02 0.14
Accelerator and linkage ............... .02 0.14
Air filter. replacing ................... .02 0.1 4
Cooling system service ............... .02 0.15
Engine drive belt service .............. .02 0.16
Idlespeed .......................... 020-19
Catalytic converter and oxygen sensors .. .02 0.19
Power steering fluid, checking level ..... .02 0.20
Spark plugs ........................ .02 0.20
Spark plugs, replacing ................ .02 0.21
Interior ventilation microfilter, replacing ... .02 0.22
Other Mechanical Maintenance ..... .02 0.22
Battery, checking. cleaning. and replacing .02 0-22
Brake fluid. replacing ................. .02 0-24
Brake pad 1 rotor wear. checking ........ .02 0.24
Brake system, inspecting ............. .02 0.25
Parking brake. checking ............... 020-25
Clutch fluid. checking ................. 020-26
Differential oil level. checking ........... 020-26
Drive axle joint (CV joint) boots. inspecting 020-27
Exhaust system. inspecting ............ 020-27
Fuel filter. replacing .................. 020-27
Fuel tank and fuel lines. inspecting ...... 020-28
Suspension. front. inspecting ........... 020-29
Suspension. rear. inspecting ........... 020-29
Tires. checking inflation pressure ........ 020-29
Tires. rotating ....................... 020-29
Transmission service. automatic ........ 020-29
Transmission service. manual .......... 020-30
Transmission fluid. checking and filling
(manual transmission)
................ 020-30
Wheels. aligning ..................... 020-30
Body and Interior Maintenance ..... 020-31
Body and hinges. lubricating ........... 020-31
Exterior washing ..................... 020-31
Interior care ........................ 020-31
Leather upholstery and trim ............ 020-31
Polishing ........................... 020-32
Seat belts .......................... 020-32
Special cleaning ..................... 020-32
Washing chassis ..................... 020-32
Waxing ............................ 020-32
Windshield wiper blade maintenance ..... 020-33