1999 BMW 525i Workshop Manual

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< 6-cylinder engine with hydraulic belt tensioners.
Use long-handled wrench to turn
A/C belt tensioner (A)
clockwise. Remove AfC belt.
* Similarly, turn main engine drive belt tensioner (B)
clockwise and remove belt.
< Some models have a dust cover over belt tensioner release
lug, which must be pried off prior to removing belt.
4 6-cylinder engine with spring-loaded belt tensioners.
Use long-handled wrench to turn
AfC belt tensioner
release lug
(A) clocltwise (against spring tension).
Remove
AfC belt.
Similarly, turn main engine drive belt tensioner lug
(B)
clocltwise and remove belt.

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020-1 8
Maintenance
V-8 engine drive belt diagram (NC belt not shown).
NOTE-
Two types of belt tensioners are used on the V-8 engines.
The tensioner shown in this procedure is for cars built up to
8/97. The later style tensioner is similar.
4 V-8 engine tensioner.
Loosen
fasteners(A) to relieve belt tension
- Remove drive belt.
4 When reinstalling belt, check that it is correctly positioned on
belt pulleys.
With bolts
(B and C) finger tight, pretension adjuster by
turning hex counterclocltwise
(arrow) to stop.
Tighten mounting bolts.
NOTE-
On 8/97 and later tensioner, turn hex on tensioner plate to
align lowerplate mounting bolt.

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Maintenance
< Remove NC compressor belt:
Loosen tensioner mounting fasteners (arrows)
Swing tensioner down to remove belt.
4 To reinstall compressor belt:
Route belt over pulleys.
* Pretension belt by turning adjuster clockwise (arrow) to
stop.
- Tighten tensioner mounting bolts (A).
Tightening torques
Fan clutch to coolant pump (left- hand thread)
with BMW tool
11 5 040
30 Nm (22 ft-lb)
without BMW tool 11 5 040
40 Nm (29 ft-lb)
Tensioner to engine block
8.8 grade
22 Nm (16 ft-lb)
10.9 grade (Ilquid-cooled alternator) 30 Nm (22 ft-lb)
Idle speed
Engine idle speed can change due to a number of factors, in-
cluding normal wear. The idle speed is electronically adaptive
and not adjustable. See
130 Fuel Injection for more informa-
tion.
Catalytic converter and oxygen sensors
OBD II enhanced emission standards require the engine
control module (ECM) to monitor the oxygen content in the
exhaust with oxygen sensors placed before and after the cat-
alytic converter. This allows for tighter control of tail pipe
emissions and also allows the ECM to diagnose converter
problems. If the ECM detects that catalytic converter or oxy-
gen sensor efficiency has degraded past a certain
prepro-
grammed limit, it will turn on the malfunction indicator light
(MIL), and store a diagnostic trouble code (DTC) in the ECM.
See OBD On-Board Diagnostics for more information on
OBD
ll systems.
Replacement of oxygen sensors at the specified intervals
he engine and emission control system will

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Maintenance
continue to operate as designed. Extending the replacement
interval may void the emission control warranty coverage.
See
180 Exhaust System for information on replacing the
oxygen sensors.
Tightening torque
Oxvoen sensor to exhaust
manifold 50 Nrn (37 ft-lb)
NOTE-
A special soclet for replacing the oxygen sensor is available
from most automotive parts stores. The soclet has
a groove
cut down one side to allow the sensor to be installed without
damaging the wire harness.
Power steering fluid, checking level
The power steering system is permanently filled and does not
have a drain. Routinely adding ATF is not required unless the
system is leaking.
4 To check power steering fluid level in fluid reservoir:
Park car on level ground with engine off.
Level is correct
if it is between MlN and MAX marks on
dipstick.
If level is below
MlN mark, add fluid to reservoir to bring
level up.
* Hand-tighten reservoir cap.
Power steering fluid
Dexron
1iiO ATF or equivalent
Spark plugs
E39 models through model year 1998 were equipped with
spark plugs with two electrodes. These are gapped to
0.7 mm
(0.028 in) by the manufacturer and are not adjustable.
Starting with 1999 models, long life spark plugs with
3 or four
electrodes were used. These can be retroactively fitted to
earlier
models. The recommended spark plug replacement
interval
forthese is 100,000 miles.The electrode gap in these
spark plugs is not adjustable.
Spark plug applications
M52 Bosch FBLDCR
M52 TU, M54 Bosch FGR7DQP or NGK BKRBEQUP
M62 to 7/97 Bosch F7LDCR or NGK BKR6EK
M62 from 7/97 Bosch F9LDCR
M62 TU Bosch FGR7DQP or NGK BKRGEQUP

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020-21
Maintenance
Spark plugs, replacing
E39 engines use a coil-over-spark plug configuration, with
one ignition coil above each spark plug. Sparks plugs should
be removed only after the engine has cooled.
Remove engine
cover(s) over ignition coils:
Remove acoustic cover over fuel injectors
I intake
manifold.
6-cylinder engine: Remove oil filler cap.
Remove plastic trim covers (arrows).
Remove cover hold-down bolts. Remove coil
cover(s)
6-cylinder engine: Temporarily reinstall oil filler cap to
keep out contaminants.
Remove ignition coil grounding harnesses (arrows). 6-cylin-
der coils shown,
V-8 engine is similar.
< Remove ignition coils:
Pull up on spring clips to disconnect ignition coil harness
connectors.
Remove coil mounting bolts. Pull coils up and off spark
plugs.
- Remove spark plugs.

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020-22 Maintenance
1
- Installation is reverse of removal, bearing in mind the
following:
Lightly lubricate new
spark plug threads with
copper-based anti-seize compound.
Thread plugs into cylinder head by hand to prevent
cross-threading.
. Be sure to reinstall and tighten coil grounds.
Tightening torque Spark plug
to cylinder head 25 Nm (18 It-lb)
Interior ventilation microfilter, replacing
Two interior ventilation microfilters are used, one on each
side of the engine compartment at the fire wall.
< To replace the microfilter, unclip the wire fastener and
remove the cover.
Lift out the filter, and replace. Left side shown; right is
similar.
Replace cover and clip wire fastener to retain cover.
Battery, checking, cleaning, and replacing
The battery Is located in the right side of the luggage compart-
ment. Simple maintenance of the battery and its terminal
connections will ensure maximum starting periormance,
especially in winter when colder temperatures reduce battery
power.
Battery cables should be tight. The terminals, cable clamps
and battery case should be free of the white deposits that
indicate corrosion and acid salts. Even a thin layer of dust
containing conductive acid salts can cause battery discharge.

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Maintenance
- To remove battery corrosion:
Disconnect battery cables. Disconnect negative (-)cable
first.
* Remove battery from trunk
Clean terminal posts and cable clamps with a wire brush.
Clean main chassis ground terminal next to battery.
Corrosion can be washed away with a
baking soda and
water solution that will neutralize acid.
Reinstall battery and reconnect cable clamps, positive
(+)
cable first.
Lightly coat outside of terminals, hold down screws, and
clamps with petroleum jelly, grease, or a commercial
battery terminal corrosion inhibitor.
WARNING
-
Battery acid is extremely dangerous. Take care to keep it
from contacting eyes, skin, or clothing. Wear eye protection.
Extinguish all
smolihg materials and do not work near any
oaen flames.
CAUTION-
Prior to disconnecting the batteg read the battery discon-
nection cautions given in
001 General Cautions and
Warnings.
NOTE-
The original equipment battery in E39 models is mainte-
nance free. The original electrolyte will normally last the
entire service life of the battery under moderate climate con-
ditions.
Battery electrolyte should be maintained at the correct level
just above the battery plates and theirseparators. The correct
level is approximately
5 mm ('14 in.) above the top of battery
plates or to the top of the indicator
marks (if applicable). The
battery plates and the indicator marks can be seen once the
fillercaps are removed.
if theelectrolyte level is low, replenish
it by adding distilled water only.
4 The original equipment BMW battery is equipped with a
built-in hydrometer "magic eye"
(arrow). Battery condition is
determined by the color of the eye:
Green: Adequate charge
* Black: Inadequate charge, recharge
Yellow: Defective battery, replace
Batteries are rated by ampere hours (Ah), the number of
hours a specific current drain can be sustained before com-
plete discharge, or by cold cranking amps (CCA), the number
of amps available to crank the engine in cold weather
condi-

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020-24
Maintenance
tions. In general, replacement batteries should always be
rated equal or higher than the original battery.
The battery is held in place by a single hand screw and plate.
A secure battery hold-down is important in order to prevent
vibrations and road shoclt from damaging the battery.
CAUTION-
Prior to disconnecting the baitem read the battery discon-
nection cautions given in
001 General Cautions and
Warnings.
NOTE-
Always disconnect the negative (-) cable first, and connect
it last. While changing the battery, clean away any corro-
sion in or around the battery tray
More battery and charging system information is in 121
Battery, Alternator, Starter.
Brake fluid, replacing
Brake fluid absorbs moisture easily, and moisture in the fluid
affects bralte performance and reliability. This is why
BMW
strictly recommends replacing the bralte fluid every two
years. When replacing or adding bralte fluid, use only new
fluid from previously unopened containers. Do not use brake
fluid that has been bled from the system, even
if it is brand
new. Use only DOT
4 brake fluid.
NOTE-
See 340 Brakes for brake fluid flushing procedures.
Brake pad 1 rotor wear, checking
Disc brakes are fitted at all four wheels. Although the brakes
are equipped with a brake pad warning system, the system
only monitors one wheel per axle. Pad thickness should be
checked whenever wheels are off or brake
worlt is being
done.
4 Disc brake pad wear can be checked through opening in
caliper:
Measure distance
(A) of brake pad "eai' to bralte rotor.
See
340 Brakes. Compare to specification below.