BMW 1989-1995 525i Service Manual page 136

117-16
CAMSHAFT TIMING CHAIN
11. Tighten top three camshaft sprocket bolts using the se-
quence listed.
Tightening Torques
• Camshaft sprocket tightening sequence
1. exhaust, left cylinder head 15 Nm (11 ft·lb)
2. exhaust, right cylinder head 15 Nm (11 ft-lb)
3. intake, left cylinder head 15 Nm (11 tt-lb)
4. intake, right cylinder head 15 Nm (1 1 ft-lb)
NOTE-
Assume left and right orientation
as
sitting in driver s
seat.
12. Remove the crankshaft and camshaft locking tools. Turn
the engine over in normal operating direction one corn-
plete revolution. Tighten the remaining sprocket mount-
ing bolts using the sequence and torque listed earlier.
13. Remove the dummy chain tensioner and install the
chain tensioner.
14. The remainder of installation is the reverse o f removal.
Tightening Torques
• Timing chain tensioner to timing
chain cover 40 Nm (30 ft·lb)
• Camshaft lubrication pipe to
camshaft bearing caps 10 Nm (89 in-lb)
• Cylinder head cover to cylinder
headl
timing chain cover
M6 10 Nm (89 in-Ib)
M7 15 Nm (11 tt-lb)
• Radiator cooling fan
to coolant pump 40 Nm (30 ft-lb)
• Spark plug
10
cylinder head 23+3 Nm (1 7±2 ft·lb)
VANOS (VARIABLE VA LVE T IMING)
1993 and later 525i models are equipped with a variable
valve liming system , called VANOS . This system is controlled
by the Motronic DME 3.3.1 engine management system and
dynamically adjusts intake camshaft timing based on engine
load , engine speed and engine temperature.
The main compo nents of the VANOS system are the con-
trol unit with piston housing and integral spool valve, and the
modified intake camshaft. See Fig. 35.
When the engine is running, the piston housing is supplied
with pressurized engine oil. At idle, the soleno id is in the off
position (de-enerqized) and valve timing is maintained in the
normal position. When the solenoid is energized, the gea r cup
piston moves forward to advance the camshaft by 12.5°.
VANOS (VARIABLE VALVE TIMING)
Fig. 35. VANOS control unit with modified intake camshaft.
WARNING-
Special BMW service tools are required to check
and repair the VANOS system. Read the proce-
dures through before beginning the job.
To test VANOS system operation
There are 3 special tools required to check VANOS opera-
tion; an electrical test lead (BMW special tool no.
12 6 41 0), an
air line fitting (BMW special tool no. 11 3 450), and a crank-
shaft TDC locking tool (BMW special tool no. 11 2300).
The test lead is used to powe r the solenoid, simulating the
ground signal from the DME control unit. The air line fitting
takes the place of the oil supply pipe fitting and simulates oil
pressure. The locking tool positions and locks the cranks haft
at TDC.
1. Remove the alternator cooling air duct.
2. Disconnect the crankcase ventilation hose fitting from
the cylinder head cover.
3. Remove the top plastic engine covers. Disconnect the
ignition coil harness connectors from the coils. Remove
the ignition coils.
4. Remove the cylinder head cover mounting bolts and
remove the cylinder head cover. Unclip and remove the
oil baffle cover from above the intake camshaft.
NOTE-
Note the arrangement of the cylinder head cover bolt
insulators and gaskets during removal.
5. Set the engine to approx imate TDC by rotating the en-
gine in the normal operat ing direction until the earn-
shaft lobes at cylinder no. 1 are facing each other. See
Fig. 8, given earlier.