2001 BMW 525i Pg 240

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Cylinder Head and valvetrain1
Double VANOS secondary timing chain components,
installing
(M52 TU, M54 engine)
< Secure camshafts in TDC position using BMW special tool
set
11 3 240.
4 If necessary, turn camshaft so that special tools are squarely
seated on cylinder head.
4 Lift timing chain and hold under tension

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-
. - - -- Cylinder Head and valvetrain]
Turn engine over twice in direction of rotation until cylinder 1
intake and exhaust camshaft lobes (arrows) face each other.
- Lock crankshaft in TDC position with BMW special tool
11 2 300.
4 Place BMW special tool set 11 3 240 over camshafts and
measure clearances.
NOTE-
@ If the exhaust side of the tool (A) is not flush with the head,
camshaft timing is incorrect. Reset camshaft timing as de-
scribed in 11
7 Camshaft Timing Chain.
Due to flexible sprocket design, VANOS unit tolerances
and play in the VANOS splines, when the camshaft timing
is set correctly, the intake side of special tool set
11 3 240
(B) may be up to 1 mm (0.04 in.) above the suiface of the
cylinder head. This is normal. Reassemble engine. Other-
wise, reset camshaft timing as describedin 1
l?Camshaft
Timing Chain.
- Remove BMW special tool 11 6 150 from front of cylinder
head.
4 Clean contact edges of cylinder head face and VANOS unit
and apply a thin coat of Three Bond
12090 or equivalent
sealing compound to surfaces.
CAUTION-
Male sure all gasket material is removed from face of cyl-
inder head. Clean sealing face and keep free of oil.
Check locating dowel
(A) and dowel sleeve (B) at top
of cylinder head for damage or incorrect installation.
- Using a new steel gasket, install VANOS unit to front of cyi-
inder head. See 117 Camshaft Timing Chain.
NOTE-
If VANOS control unit is being replaced, be sure to check and
adjust camshaft timing as described in 117 Camshaft Tim-
ing Chain.
- Reinstall engine lifting eye.
- Reconnect electrical harness connectors to camshaft posi-
tion sensors and
VANOS solenoid valves.

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Table d. Valve guide specifications
Specifications
All engines (1997-2002)
Valve guide wear, maximum 0.5 mrn (0.020 in)
(valve tilt clearance
measured
with new valve)
Valve guide inside diameter,
installed
(tolerance per IS0 allowance H7)
Standard 6.0 mm (0.236 in)
Oversize
1 6.1 mrn (0.240 in)
Oversize 2 6.2
mm (0.244 in)
Valve stem oil seals
The purpose of the valve stem oil seal is to prevent excess oil
from entering the combustion chamber. The sign of faulty
valve stem oil seals is excessive oil consumption and smoke
from the exhaust immediately after starting and during decel-
eration.
NOTE-
Valve stem oil seals should not be reused. If valves are re-
moved, new valve stem oil seals should be installed.
Valve stem oil seal replacement requires that the cylinder
head be disassembled and the valves removed as described
above under Valves, removing and installing.
NOTE-
BMW special tools are available to remove the valve stem oil
seals. As an alternative, standard valve seal removal tools
are available from most automotive parts stores.
Lubricate new seal and install using hand pressure only. Be
sure to install valve spring
seat(s) before installing seal.

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[Camshaft Timing Chain
4 Camshaft locking tool set, 6-cylinder
(Tool No. BMW
11 3 240)
- 4 Crankshaft seal installation bushing. 6-cylinde~
4 Secondary chain tensioner locking pin set. 6-cylinder
(Tool No.
BMW 11 3 290)
11 3292
4 Secondary chain tensioner loclting pin, V-8
(Tool No. BMW 11 3 310)
4 Air line fitting
(Tool No. BMW
11 3 450)
4 Protractor
(Tool No. BMW
11 3 460)

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Camshaft Timing Chain
4 Unscrew and remove cylinder head cover studs (arrows) at
rear of cylinder head.
% Secure camshafts in TDC position using BMW special tool
set
11 3 240.
4 Remove access plugs (arrows) from VANOS control unit.

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. .. ~-
Camshaft Timing Chain -
4 Secure camshafts in TDC position using BMW special tool
set
11 3 240.
- Disconnect compressed air line, leaving compressed air fit-
ting attached to VANOS control unit.
NOTE -
Oil will drain from pressure line. Have a container and rags
ready
4 Unscrew sealing plugs from VANOS control unit (arrows).
NOTE-
Oil will drain from sealing plug bores. Have a container and
rags ready
4 Pull sealing caps straight out of VANOS control unit with
BMW special tool 11 6 170, or with short nose pliers.
NOTE-
Additional oil may drain from VANOS control unit.
4 Remove set screws (left-hand thread) on ends of intake and
exhaust camshafts.
NOTE-
Set screws have left hand threads. Remove with a clockwise
motion.

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Camshaft Timing chain1
< With compressed air line connected, turn engine at least
twice in direction of rotation until cylinder
1 intake and ex-
haust camshaft lobes (arrows) face each other.
Do not rotate engine counterclockwise to reach the top dead
center position. Instead, complete another two complete ro-
Remove sealing plug from bore at bellhousing. Secure crank-
shaft in
TDC position with BMW special tool 11 2 300 (ar-
row).
- Remove cylinder head cover studs at rear of cylinder head.
< Place BMW special tool 11 3 240 over camshafts ends and
measure clearance of tool to cylinder head surface.
NOTE-
If the exhaust side of the tool (A) is not flush with the head,
adjust camshaft timing as described below.
Due to flexible sprocket design and VANOS control unit tol-
erances and play, the
intake side of special tool 11 3 240
(B) may be up to 1 mm (0.04 in) above the surface of the
cylinder head. This is normal. Reassemble engine. Other-
wise, adjust camshaft timing as described below.
- Remove double VANOS control unit. See VANOS control
unit, removing
(M52 TU and M54 engines).
< Press down on secondary chain tensionerand lock into place
using BMW special tool
11 3 292 or equivalent pin or drift.

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Camshaft Timing chain]
4 Pull out exhaust camshaft splined shaft to stop.
- Make sure camshafts are secured in TDC position using
BMW soecial tools 11 3 240 and 11 3 244.
4 Preload primary chain tensioning rail:
Tighten adjusting screw on
BMW special tool 11 4 220.
Tightening torque
Primary chain tensioner preload
0.7 Nm (6 in-lb)
4 Preload exhaust camshaft spring plate by pressing on im-
pulse wheel. Tighten mounting nuts
(arrows) by hand. Do
not tighten fully.