BMW 1989-1995 525i Service Manual page 140

117-20
CAMSHAFT TIMING CHAIN
6. Turn the secondary timing chain sprockets so that they
contact the right-hand stop (clockwise as viewed from
the front of the engine).
7. While slowly pushing the VANOS control unit towards
the camshaft. turn the secondary sprockets counter -
clockwise only enough to mesh the gear cup (external
splines) with the camshaft sprocket splines.
CAunON -
It is
critical that the secondary sprockets be turned
only the minimum amount necessary to engage
the gear cup. If this procedure is done incorrectly.
the VANOS system may not function correctly and
engine damage could result .
8. Slide the VANOS unit all the way in until it is fully seat-
ed. Install and tighten the VANOS control unit nuts.
NOTE-
As the control unit is installed. the secondary gears will
rotate in the counterclockwise direction.
It
may be nec-
essary to gu ide sprockets counterclockwise
as
the con-
trol unit is installed.
9. Connect the harness connector to the VANOS sole-
noid. Using new seals. install the oil line fitting .
Tightening Torques
• VANOS control unit to cylinder head
M6 nut. 10 Nm (89 in-Ib)
M8 bolt 22 Nm (17 ft-Ib)
• VANOS oil supply line
to VANOS control unit 32 Nm (24 ft-Ib)
10. Slowly unlock and release the secondary chain ten-
sioner.
11 . Preload the primary chain by tightening BMW special
tool no. 11 3 390 (dummy chain tensioner) to 1.3 Nm
(11 in-Ib). Then tighten the exhaust camshaft sprocket
mounting bolts alternately in two stages.
Tightening Torque
• 1993 and later M50TU engine
Secondary timing chain sprockets to camshafts
(Torx bolts)
stage 1 5 Nm (44 in-lb)
stage 2 22 Nm (17 tt-lb)
VANOS (VARIABLE VALVE TIMING)
12. Remove the flywheel locking tool from the transmiss ion
bellhous ing. Remove the camshaft locking tool from
the rear of the cylinder head.
13. Turn the engine over by hand at least two full crank-
shaft rotations . Reinstall the camshaft locking tool and
the flywheel locking tool to make sure all adjustments
are correct.
If
the settings are correct . remove the lock-
ing tools.
14. Remove BMW special tool 11 3 390 (dummy chain ten-
sioner) from the side of the cylinder head. Install the pri-
mary chain tensioner so that the cutout in the tensioner
piston engages the chain rail as shown earlier in Fig.
21. Using new seals. install and tighten the access
plugs in the VANOS control unit.
Tightening Torque
• Access plugs to
VANOS control unit. 50
+
5 Nm (30
+
3 ft-Ib)
• Primary camshaft timing chain tensioner
plug to tensioner sleeve 50 Nm (37 ft-Ib)
15. Install the oil baffle cover above the intake camsha ft.
Install the three cylinder head cover mounting studs to
the rear of the head. Install the cylinder head cover.
Tightening Torque
• Cylinder head cover
to cylinder head . . . . . . . . . . . . . . .. 10 Nm (89 in-Ib)
16. Installation of the remaining parts is the reverse of re-
moval.
NOTE -
Be sure to install the ground wires at the cylinder head
cover mounting studs and at the front of the cylinder
head.