2001 BMW 525i service

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1 17-2
Camshaft Timing Chain
This repair group covers timing chain and VANOS repair
information for the following engines:
M52 (Single VANOS 6-cylinder engine)
M52
TU and M54 (Double VANOS engines)
M62 (Non VANOS
V-8 engine)
NOTE-
The M62 TU V-8 engine with VANOS Variable Camshaft
Timing repair information is not included.
NOTE-
See 100 Engine General for engine code and application
information.
Worn timing chains and sprocltets can lead to noisy operation
and erratic valve timing. Afaulty tensionercan also cause tim-
ing chain noises.
For specific repair procedures, refer to the appropriate repair
group:
020 Maintenance
113 Cylinder Head Removal and Installation
119 Lubrication System
121 Ignition System
170 Radiator and Cooling System
Special tools
Special BMW service tools are needed to perform the service
and repairs procedures covered in this repair group. Many of
these tools are expensive and only available through an au-
thorized BMW dealer. Be sure to read each procedure thor-
oughly before starting a job to determine which special tools
will be necessary.
In addition, Double VANOS system diagnosis can only be
carried out by using BMW specific electronic scan tools, such
as BMW
DISplus, MoDiC or equivalent.
4 Torque wrench wl flex extension
(Tool No. BMW 00
9 250)

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I Camshaft Timing Chain
Mark 0" location on socket (arrow). Tighten hub bolt in four
stages.
Tightening torque Vibration damper
hub to cranlrshaft
Stage 1 100 Nm (74 it-lb)
Stage
2 60" Torque angle
Stage
3 60" Torque angle
Stage
4 30" Torque angle
- install vibration damper and mounting bolts
NOTE-
Male sure to align vibration damper with locating dowel pin
in hub.
Tightening torque Vibration damper to
cranltshait hub (ME) 22 Nm (16 ft-lb)
- Install drive belts. See 020 Maintenance.
- Install cooling fan. See 170 Radiator and Cooling System.
- Replace under engine splash shield, then reconnect nega-
tive battery cable.
!/ANBS CONTROL UNIT AND
TIMING CHAIN (M52 ENGINE)
VANOS control unit, removing (M52 engine)
NOTE-
Special BMW service tools are required to remove and in-
stall the
VANOS control unit. Read the procedure through
before starting the job.
If the camshafts are notproperly timed, the pistons can
contact the valves.
- Disconnect negative (-) cable from battery.
CAUTION-
Disconnecting the battery may erase fault code(s) stored in
control module memory. Prior to disconnecting the
battev,
check for fault codes using special BMW diagnostic equip-
ment.
* Prior to disconnecting the battery, read the battery dis-
connection cautions given in
001 General Cautions
and Warnings.

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Camshaft Timing Chain
VANOS timing, checking and adjusting
(M52 engine)
NOTE-
* Special BMW service tools are required to remove and in-
stall the VANOS control unit. Read the procedure through
before starting the job.
If the camshafts are not properly timed, the pistons can
contact the valves.
- Disconnect negative (-) cable from battery.
CAUTIOG Disconnecting the battery may erase
faultcode(s) storedin
control module memory. Prior to disconnecting the battery,
checlc for fault codes using special BMW diagnostic equip-
ment.
Prior to disconnecting the battery, read the battery dis-
connection cautions given in
001 General Cautions
and Warnings.
- Remove viscous clutch cooling fan. See 170 Radiator and
Cooling
System.
CAUTIOG The radiator cooling fan nut
(32 mm wrench) has left-hand
threads.
4 Remove ignition coils:
Disconnect ignition coil electrical harness connectors.
Remove coil mounting fasteners and remove coils.
Remove
spark plugs.
NOTE-
Make note of ignition coil ground strap locations.

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... -.
Camshaft Timing chain1
Timing chains, removing
(M52 TU and M54 engines)
Camshaft timing chain removal requires that the oil pan be re-
moved. See
119 Lubrication System. Also required is re-
moval of the VANOS control
unit and disassembly of the
intake and exhaust camshaft sprocket assemblies as de-
scribed earlier in this repair group.
Special BMW
service tools are needed for timing chain re-
moval and installation. The special tools assure proper timing
of the valvetrain. Precise
marlts to set the timing on the cam:
shafts are not provided for reassembly. Read the procedures
through before beginning the job.
CA
UTION-
If the camshafts are not properly timed, the pistons can con-
tact the valves.
- D~sconnect negative (-) cable from battery.
CAUTION-
* Disconnecting the battery may erase fault code@) stored in
control module memory. Check for fault codes using spe-
cial
BMW diagnostic equipment.
Prior to disconnecting the battery, read the battery dis-
connection
cautfons given in 001 General Cautions
and
Warninqs.
- Remove VANOS control unit. See VANOS control unit, re-
moving
(M52 TU and M54 engines).
Remove sealing plug from crankcase below starter and se-
cure crankshaft with
BMW special tool ll 2 300.
Drain engine cooling system. See 170 Radiator and Cool-
ing System.
Remove belt driven cooling fan, fan shroud, and thermostat
housing. See
170 Radiator and Cooling System.
Remove drive belts. See
020 Maintenance.
NOTE-
Mark direction of belt rotation if reusing belt.
- Remove water pump pulley fasteners and pulley.
- Drain engine oil and remove oil pan as described in 119
Lubrication System.

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11 7-66
I Camshaft Timing Chain
4 install cylinder head cover:
Check for correct seating of half-moon seals
(A) in back of
cylinder head cover.
Use a small amount of Three Bond
1209 8 or equivalent
sealant at corners
(B) of half-moon cutouts. Seal corners
in front of cylinder head at VANOS control unit.
Tightening torque
Cylinder head cover to cylinder head
10 Nm (89 in-lb)
- Remainder of reassembly is reverse of removal, noting the
following:
Secure all coolant hoses, thermostat housing, engine cool-
ant drains.
Install new engine oil filter and oil. See
119 Lubrication
System.
Refill and bleed cooling system as described in
170 Radi-
ator and Cooling system.
Use scan tool to check VANOS operation with engine
idling.
Tightening torques Coolant drain plug to cylinder block
25 Nm (18 ft-lb)
Radiator cooling fan (viscous clutch)
to coolant pump
40 Nm (30 ft-lb)
Radiator drain screw to radrator 2.5 Nm (22 in-lb)
Vibration damper hub to crankshaft 41 0 Nm
(300 ft-ib)
TIMING CHAIN
(M62 ENGINE TO 911998)
Timing chains, removing
(M62 engine to 911 998)
Camshaft timing chain removal requires that the engine oil
pan be removed.
Special
BMW service tools are needed for timing chain re-
moval and installation procedures. The special tools assure
propertiming of thevaivetrain. Precise marks to set the timing
on the camshafts are not provided for reassembly. Read the
procedures through before beginning the job.
CAUTION-
Special BMW service tools are needed for this procedure.
Read the procedure through before beginning the job. If the
camshafts are notproperly timed, the pistons can contact the
valves.

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120 lgnition System
...................... General
Special tools ...................
Warnings and cautions ...........
Engine management .............
................. lgnition system
Ignition system. troubleshooting
....
... Oscilloscope diagnostic diagrams
................ Misfire detection
............. Ignition System Service 120-9
.................... Ignition firing order 120-9
.............. Disabling ignition system 120-10
................... Checking for spark 120-1 0
lgnition coil assembly.
................. testing and replacing 120-1 0
.............. Crankshaftspeedsensor 120-12
............. Camshaft position sensors 120-1 4
...................... Knocksensors 120-16

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ignition System
Disabling ignition system
The ignition system operates in a lethal voltage range and
should be disabled any time engine service or repair work is
being done that requires the ignition to be switched on.
The engine management system can be disabled by remov-
ing the DME main relay. The relay is located in the electronics
box (E-box) in the left rear of the engine
compartment, be.
neath the interior microfilter housing.
CAUTION- Relay locations may
vary. Use care when identifying relays.
See
610 Electrical Component Locations.
Checking for spark
CAUTION-
If
a spark test is done incorrecth damage to the Engine Con-
trol Module
(ECM) or the ignition coils may result.
NOTE-
Spark plug replacement is covered in 020 Maintenance.
Check~ng for spark is d~fflcult on englnes wlth d~str~butorless
ignition systems.
Try removing the spark plugs and inspecting for differences between them.
A poor-firing plug may be wet with fuel and/or ~. - ~
black and sooty, but not always. If a coil is not operating, the
engine management system will electrically disable the fuel
injector to that cylinder. The key is to look for differences be-
tween cylinders.
Ignition coil assembly, testing and
replacing
C4 UTION-
Use a digital multimeter for the following tests. I
- Remove plastic engine cover from top of valve cover by pry-
ing off bolt covers and removing cover mounting bolts.
- Raise car slowly while constantly checking position of jack
and car.
- Disconnect harness connector from coil. Connect multimeter
between terminal 15
(+) in connector and ground.
4 Terminal identification are typically molded into connector. In
photo, terminals are from left to right: 1,
4a, 15.

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.
Battery, Starter, Alternator
Table b. Specific gravity of battery electrolyte at 27°C (80°F)
Specific gravity State of charge
1.265 Fully charged
1.225 75% charged
1.190 50% charged
1.155 25% charged
1.120 Fully discharged
if the specific gravity is at
orabove 1.225, butthe battery lacks
Dower for
startinq, determine the battew's service condition
with a load volta& test. if the average specific gravity of the
six cells is below 1.225, remove the battery from the luggage
compartment and recharge.
Battery open-circuit voltage test
Before testing, load battery with 15 amperes for one minute
with battery load-tester or turn on headlights for about one
minute without engine running. Connect digital voltmeter
across battery terminals. Open-circuit voltage levels are giv-
en in Table
c. Open-circuit voltage and battery charge.
If open-circuit voltage is
OK but battery still lacks power for
starting, perform a load voltage test.
If open-circuit voltage is
below 12.4 volts, recharge battery
and retest.
Table c. Open-circuit voltage and battery charge
Open-circuit voltage State of charge
12.6 V or more
12.4 V
12.2v
12.0 v
Fully charged
75% charged
50% charged
25% charged
11.7Vorless Fully discharged
Battery load voltage test
A battery load tester is required for a load voltage test. The
test is made by applying a high resistive load to the battery
terminals and then measuring battery voltage. The battery
should be
fully charged forthe most accurate results. The bat-
tery cables must be disconnected before
malting the test. Re-
place the battery if the voltage is below that listed in Table d.
Battery load test
- minimum voltage.