1997 BMW 525i ECO

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Cylinder Head Removal and Installation
4 If applicable, remove secondary air injection pump:
Disconnect hose at one-way valve
(A).
Remove bolts at support bracket on strut tower (arrows).
Disconnect electrical harness from bottom of secondary
air injection pump.
Remove mounting bracket from strut tower.
4 Remove ignition coils:
* Disconnect ignition coil harness connectors.
Remove coil mounting fasteners.
Remove coils.
* Remove ground straps.
CA UTIOI\C
Note location of all ground wires. Failure to reinstall grounds
can result in permanent damage to engine control module or
ignition system components.
Set coil harness to side of engine compartment
- Remove cylinder head cover mounting fasteners and remove
cylinder head cover.
NOTE-
The cylinder head cover mounting bolt insulators and gas-
ltets should be reinstalled in their original locations. Male
note of their arrangement during removal.
- Remove spark plugs
4 Remove oil baffle cover from above intake camshaft.

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- -
-- .- Cylinder ~ead~ernoval and Installation I - -.
Remove VANOS unit:
Remove engine lifting eye.
- Remove VANOS mounting nuts (arrows) and pull VANOS
unit and metal gasket off.
CAUTION-
Do not crank the engine with VANOS unit removed. Pis-
tonhalve inteiference may result.
NOTE-
The VANOS unit will contain a small quantity of oil. Place
shop towel to catch oil as unit is removed or tilted.
CAUTION-
If the VANOS adjustment unit is replaced, or if operations are
completed that may change the timing of
the camshafts, the
camshaft timing must be checked. See
11 7Camshaft Timing
Chain.
4 Remove primary camshaft chain tensioner cylinder (arrow).
CAUTION-
Primary camshaft chain tensioner is under spring pressure.
Press down on secondary chain tensionerand lock into place
using
BMW special tool 11 3 291, or a thin drifl or pin.

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11 3-35
- cylinder Head Removal and Installation] -
< Lift off exhaust and intake sprocltets together with secondary
chain, thrust spacer
(A), and splined shafl (B).
CAUTION-
Splined shafts share the same part number for both intake
and exhaust camshafts. Used splined shafts must be
rein-
stalled in their original positions.
Remove exhaust camshaft splined sleeve
(A) and shaft (B).
Remove secondary chain tensloner mounting bolts (arrows)
and remove tensioner with retaining pin in place.

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11 3-38
I Cylinder Head Removal and Installation
< Turn eccentric shaft of special tool to pretension intake cam-
shaft bearing caps. Remove nuts on all intake camshaft bear-
ing caps.
- Slowly release tension on eccentric shaft and remove BMW
spec~al tools. Remove bearing caps and set as~de in order.
Remove camshaft and store safely.
- Repeat procedure for exhaust camshaft.
4 Secure hydraulic lifters in lifter bores using BMW speclal tool
11 3 250, or remove lifters using a magnetic pick-up tool.
With lifters secure or removed, lift out camshaft bearing car-
riers from cylinder head.
Use care to not let hydraulic lifters fall out as camshaft car-
rier is removed.
Hydraulic lifters should be stored
ln an uprightpositlon.
Used hydraulic lifters must be reinstalled into their orig-
inal lifter bores.
4 Remove intake camshaft position sensor (arrow) from side
of cylinder head.
4 Remove secondary chain lowerguide bolts (arrow). Remove
chain guide.

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. - -- -
Cylinder Head Removal and Installation --
Remove bolts (arrows) holding timing chain cover to cylinder
head. (Photo shows camshafts and camshaft bearing caps in
place).
4 Using BMW special tool 11 2 250 or equivalent, loosen cylin-
der head bolts in several stages, in sequence shown. Discard
head bolts.
NOJE-
BMW special tool 11 2 250 is a thin-walled Torx El2 socket
with an extended reach. The cylinder head bolts are re-
cessed into the head below the
camshaft towers with little
working space.
- Lift off cylinder head. Refer to 116 Cylinder Head and Val-
vetrain for cylinder head reconditioning information.
Cylinder head, installing, M52 TU and M54
engines
Clean cylinder head and gasket surfaces of cylinder bloclc
and all timing chain covers.
CAUTION- Remove foreign matter and liquid from bolt holes. Trapped oil
or coolant in bolt holes can cause damage to
blocl~,
CAUJION-
Do not use a metal scraper or wire brush to clean the alumi-
num cylinder head or pistons. If necessary, use a hard wood-
en orplastic scraper. Also available are abrasive discs to be
used in conjunction with an electric drill. Be sure to use the
correct disc for the type of metal being cleaned.
Evaluate cylinder head as shown in
116 Cylinder Head and
Valvetrain.
NOTE- If the cylinder head has been machined, a special 0.3
mm
(0.01 1 in.) thicker gasket should be installed. The thicker
gasket is available from an authorized
BMW dealer and
should be marked accordingly
Cylinder head and valve specifications are covered in 116
Cylinder Head and Valvetrain.

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. - ..
Cylinder Head Removal and installation] --
- Secure cylinder head bolts by torquing an additional 90"
each for Stage 2 and 3.
Tightening torques
Cylinder head to engine block
(aluminum block)
Stage
1 40 Nm (30 it-lb)
Stage 2 +90°
Stage 3 80'
4 lnstall intake camshaft position sensor (arrow).
4 Install lower secondary chain guide. Tighten tom bolts to
specifications. The bolt on the intake camshaft side is long
and extends into the engine block.
4 Install and tighten cylinder head-to-lower timing chain cover
bolts (arrows). (Photo shows camshafts in place).
Tightening torque Secondary chain guide to cylinder head
10 Nm (89 in-lb)
Cylinder head to lower timing chain cover
M6 10 Nm (89 in-lb)
M7 15 Nm (1 1 it-lb)

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1 13-46
Cylinder Head Removal and Installation
Double
VANOS Timing
Chain Components
1. Impulse wheel mounting nut
2. Exhaust camshaft impulse
wheel
3. Spring plate, exhaust
4. Thrust spacer (T
= 3.5 mm)
5. Splined shaft
6. Torx screw
7. Exhaust camshaft secondary
sprocket
8. Secondary timing chain
9. Splined sleeve
10. Primary sprocket
11. Threaded locating stud
12. Secondary chain tensioner
13. Secondary chain lower guide
14. Sprocket mounting nut
15. Spring plate, intake
16. Splined shaft
17. lntakecamshaft sprocket
18. Locating stud
19. Thrust spacer
20. Intake camshaft impulse wheel
Double VANOS timing chain components,
installing,
M52 TU and M54 engines -
4 Slide impulse wheel on intake camshaft, aligning boss with
raised portion on camshaft
(arrow).

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I Cvlinder Head Removal and Installation
4 Install secondary chain tensioner on cylinder head (arrows).
Keep tensioner compressed using BMW special tool 11 3
291 or suitable pin.
< Install exhaust camshaft splined sleeve. Confirm that gap in
sleeve splines aligns with corresponding gap in
camshaft
splines (arrows).
Slide splined shaft onto exhaust camshaft. Be sure that locat-
ing tooth of shaft fits into spline gaps of camshaft and splined
sleeve
(arrows).
- Push splined shaft in further to rotate splined sleeve until the
three threaded holes in primary chain sprocket are centered
in the small slots of the splined sleeve.
4 Place intake and exhaust sprockets in BMW special tool 11 6
180. Position spline gap on intake sprocket (arrow) as shown
and place secondary chain on sprockets.