1999 BMW 540i check engine

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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.

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7 Maintenance
< Unbolt caliper from steering arm to properly inspect:
Brake pad thickness
(A)
Brake rotor
Condition of caliper seal
(B)
Condition of caliper slider bolts (C)
NOTE-
Brake caliper removal and installation procedures are given
in
340 Brakes.
Brake pad lining minimum thickness
Dimension
A 3.0 mm (0.12 in)
Brake system, inspecting
Routine maintenance of the brake system includes maintain-
ing the brake fluid in the reservoir,
checking bralte pads for
wear, checking parking brake function, and inspecting the
system for fluid lealts or other damage:
- Check that bralte hoses are correctly routed to avoid chafing
or
Itinking.
- lnspect unions and brake calipers for signs of fluid leaks.
- lnspect rigid lines for corrosion, dents, or other damage.
- Inspect flexible hoses for cracking
- Replace faulty hoses or lines as described in 340 Brakes.
WARNING-
Incorrect installation or overtightening hoses, lines, and
unions may cause chafing
orlealage. This can lead to partial
Parking brake, checking
The parking brake system is independent of the main braking
system and may require periodic adjustment depending on
use. Adjust the parking brake if the brake lever can be pulled
up more than
8 clicks. Check that the cable moves freely. A
description of the parking brake and
parlting bralte adjust-
ment can be found in
340 Brakes.

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020-26
Maintenance
NOTE-
The parking brake may lose some of its effectiveness if it is
not used frequently This is due to corrosion build-up on the
parking brake drum. To remove corrosion, apply the parking
brake just until it begins to grip, then pull the lever up one
more stop (click). Drive the car approximately 400 meters
(1,300
ft.) and release the brake. To recheck the adjustment
of the parking brake see
340 Brakes.
Clutch fluid, checking
In cars equipped with manual transmission and clutch, the hy-
draulic clutch and the brake system share the same reservoir
and the same bralte fluid. Clutch fluid level and brake fluid lev-
el are checked at the same time.
NOTE-
* See 340 Brakes for more information.
See
210 Clutch for information on the clutch and the
hydraulic clutch operating system.
Differential oil level, checking
The E39 differential is filled with lifetime oil that ordinarily
does not need to be changed.
BMW recommends using only
a specially formulated synthetic gear oil
(SAF-XO) that is
available through an authorized
BM\N dealer parts depart-
ment. For additional information on this lubricant and any
other lubricants that may be compatible, contact an
authorized
BMW dealer service department.
< Check rear differential oil level at filler plug (arrow).
- Check lubricant level with car on a level surface:
Level is correct when fluid just reaches edge of filler hole.
If necessary, top up fluid.
Replace filler plug sealing ring.
Install and tighten oil filler plug when oil level is correct.
NOTE-
Use either a 14 mm or 17 mm Allen socket to remove the
drain plug.
If the car is raised in the air, it should be level when
checking or filling final drive fluid level.
Tightening torque
Filler plug to final drive housing 70 Nrn (52 it-lb)

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.-. -
Maintenance
Drive axle joint
(CV joint) boots, inspecting
CVjoint protective boots must be closely inspected forcracks
and any other damage that will allow contaminants to get into
the joint.
If the rubber boots fail, the water and dirt that enter
the joint will quickly damage it.
NOTE-
Replacement of the CVjoint boots and inspection of the
joints are described
in 331 Final Drive.
Exhaust system, inspecting
Exhaust system life varies widely according to driving habits
and environmental conditions. If short-distance driving pre-
dominates, the moisture and condensation in the system will
not fully dry out. This will lead to early corrosion damage and
more frequent replacement.
Scheduled maintenance of the exhaust system is limited to
inspection:
* Check to see that all the hangers (arrow) are in place and
properly supporting the system and that the system does
not strike the body.
Check for restrictions due to dents or
kinlts,
Check for weakness or perforation due to rust.
NOTE-
Alignment of the system and the location of the hangers are
described in
180 Exhaust System.
Fuel filter, replacing
The fuel filter is located beneath the center of the car, approx-
imately under the driver's seat.
A protective cover must be
removed to access the filter.
4 Fuel filter for M62 engine (arrow)
- Disconnect battery negative (-) cable
CAUTIOI\C
Disconnecting the battery cables may erase fault codes
stored
in engine control module memory.
WARNING -
Fuel will be expelled forcibly when the filter is removed. Do
notsmoke or work near heaters orother fire hazards. Keep a
fire extinguisher handy

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020-28
1 Maintenance
- When replacing fuel filter:
Use appropriate hose clamping device to clamp off filter
inlet and outlet hoses to lessen fuel spillage.
Loosen center clamping bracket and hose clamps on
either end of filter.
Note arrow or markings indicating direction of flow on
new filter.
Install new filter using new hose clamps
- Drain fuel filter from inlet side into a container and inspect
drained fuel.
Checlc for rust, moisture and contamination.
I - I < If fuel filter is equipped with fuel pressure regulator:
I 2 / Remove vacuum hose (1)
Pull out locking clip (2).
- Remove fuel pressure regulator (3).
Install pressure regulator in new filter.
Clean thoroughly around the filler connections before
removing them.
After assembly, check filter connections carefully for
I
I lealcs before installing cover.
NOTE- ~-
Additional informarion about the fuel filler assembly is in 160
Fuel Tank and Fuel Pump.
Fuel tank and fuel lines, inspecting
lnspectthe fuel tank, fuel lines, and fuel system fordamage or
lealts. Checlc for fuel lealts in the engine compartment or fuel
odors in the passenger compartment. Check for any evapora-
tive emissions hoses that may have become disconnected,
checking carefully at charcoal canister and evaporative emis-
sions purge system. See
130 Fuel Injection and 160 Fuel
Tankand Fuel Pump for component locations and additional
information.
WARNING-
When checlcing for fuel leal(s, the engine must be cold. A hot
exhaust manifold or exhaust system could cause the fuel to
ignite or explode causing serious personal injury Ventilate
the work area and clean up spilled fuel immediately.

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Maintenance
Suspension, front, inspecting
Inspection of the front suspension and steering includes a
check of all moving parts
forwear and excessive play. Inspect
ball joint and tie-rod rubber seals and boots for cracks
ortears
that could allow the entry of dirt, water, and other
contaminants. See
310 Front Suspension.
Suspension, rear, inspecting
Differential and rear drive axle service consists of checking
and changing the gear oil, inspecting for leaks, and checking
the drive axle
CV joint boots for damage.
The areas where
lealts are most likely to occurare around the
drive shaft and drive axle mounting flanges. For more infor-
mation on identifying oil leaks and theircauses, see
330 Rear
Suspension and
331 Final Drive.
Tires, checking inflation pressure
Correct tire pressures are important to handling and stability,
fuel economy, and tire wear. Tire pressures change with tem-
perature. Pressures should be
checked oRen during season-
al temperature changes. Correct inflation pressures can be
found on the driver's door pillar and in the owner's manual.
Note that tire pressures should be higher when the car is
more heavily loaded.
WARNING-
Do not inflate any tire to a pressure higher than the tire's max-
imum inflation pressure listedon the sidewall. Use care when
adding air to warm tires. Warm tire pressures can increase as
much as
4 psi (0.3 bar) over their coldpressures.
Tires, rotating
BMW does not recommend tire rotation. Due to the car's sus-
pension design, the front tires begin to wear first at the outer
shoulder and the reartires begin to wearfirst at the middle of
the tread or inner shoulder. Rotating the tires may adversely
affect road handling and tire grip.
Transmission service, automatic
The automatic transmissions installed in E39 models are
filled with special automatic transmission fluid. The transmis-
sion lubricant type can be found on the "type-plate" on the
side of the transmission. The recommended lubricants are
listed earlier in this repair group. See Fluids and lubricants.
If in doubt, consult an authorized BMW dealer for alternate

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020-30
Maintenance
fluid use and the most-up-to-date information regarding
transmission operating fluids.
The automatic transmission is not equipped with a dipstick.
Therefore, checking the ATF level is an involved procedure
which includes measuring and maintaining a specified ATF
temperature during the checking procedure.
For more complete
ATF service information, including
checking
ATF level and ATF filter replacement procedures,
see
240 Automatic Transmission.
Transmission service, manual
Manual transmission service consists of inspecting for leaks
and checking the fluid. Evidence of transmission leaks is
like-
ly to be seen around the driveshaft mounting flange and at the
bottom of the bellhousing.
NOTE-
For more information on identifying oil
leaks and their
causes, see 230 Manual Transmission and210 Clutch.
Transmission fluid, checking and filling
(manual transmission)
Tne manual transmss'on inslalleo 'n rne E39 models s f;lled
with a special liierime iluid (ivlTF-LT-I). oi. ordinarily
does
not need to be changed.
< Check manual transmission oil level at transmission filler plug
(A). Make sure car is on level surface.
NOTE- Transmission fluid level
checking and replacement
procedures are covered in 230 Manual Transmission.
Wheels, aligning
BMW recommends checking the front and rear alignment
once a year and whenever new tires are installed.
NOTE-
See 320 Steering and Wheel Alignment for a more detailed
discussion of alignment requirements and specifications.

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Two common causes of driveability problems are incorrect
system voltage and bad grounds.
System voltage
Digital motor electronics (DME) requires that the system (bat-
tery) voltage be maintained within a narrow range of DC volt-
age.
DC voltage levels beyond or below the operating range,
or any
AIC voltage in the electrical system can cause havoc.
When troubleshooting an illuminated MIL, make sure the bat-
tery is fully charged and capable of delivering all its power to
the electrical system. An undercharged battery can amplify
AIC alternator output ripple.
To
make a quick check of the battery charge, measure the
voltage across the battery terminals with all cables attached
and the ignition off.
Afully charged battery will measure 12.6
volts or slightly more, compared to 12.1 5 volts for a battery
with a 25% charge.
The DME system operates at low voltage and current levels,
making it sensitive to small increases in resistance. The elec-
trical system is routinely subjected to corrosion, vibration and
wear, so faults or corrosion in the wiring harness and connec-
tors are not uncommon. Check the battery terminals
forcorro-
sion or loose cable connections. See 121 Battery, Starter,
Alternator for additional information.
If a battery cable connection has no
v~sible faults but is still
suspect, measure the voltage drop across the connection. A
large drop indicates excessive resistance, meaning that the
connection is corroded, dirty, or damaged. Clean or repairthe
connection and retest.
NOTE-
For instructions on conducting a voltage drop test and other
general electrical troubleshooting information, see
600 Elec-
trical System-General.
Visually inspect all wiring, connectors, switches and fuses in
the system. Loose or damaged connectors can cause inter-
mittent problems, especially the small terminals in the ECM
connectors. Disconnect the wiring harness connectors to
check for corrosion, and use electrical cleaning spray to re-
move contaminants.
Main grounds
Good grounds are critical to proper DME operation. If a
ground connection has no visible faults but is still suspect.
measure the voltage drop across the connection. A large volt-
age drop means high resistance. Clean or repair the connec-
tion and retest.
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