timing chain BMW 740i 1999 E38 M62TU Engine Workshop Manual

VANOS TRANSMISSION:The primary and secondary timing chain sprockets are inte-
grated with the VANOS transmission. The transmission is a self contained unit.
The controlled adjustment of the
camshaft occurs inside the “transmis-
sion”. Similar in principle to the six
cylinder engine VANOS systems, con-
trolled oil pressure moves the piston
axially.
The helical gear cut of the piston acts
on the helical gears on the inside sur-
face of the transmission and rotates
the camshaft to the specific advanced
or retarded angle position.
Three electrical pin contacts are locat-
ed on the front surface to verify the
default maximum retard position using
an ohmmeter. This is required during
assembly and adjustment. (see service
notes further on).
OIL DISTRIBUTION FLANGES:The oil distribution flanges are bolted to the front surface
of each cylinder head. They provide a mounting location for the VANOS solenoids as well
as the advance-retard oil ports from the solenoids to the intake camshafts.
CAMSHAFTS: Each intake camshaft has
two oil ports separated by three sealing rings
on their forward ends.
The ports direct pressurized oil from the oil
distribution flange to the inner workings of
the VANOS transmission.
Each camshaft has REVERSEthreaded
bores in their centers for the attachment of
the timing chain sprockets on the exhaust
cams and the VANOS transmissions for
each intake camshaft as shown.
CAMSHAFT POSITION IMPULSE WHEELS:The camshaft position impulse wheels pro-
vide camshaft position status to the engine control module via the camshaft position sen-
sors. The asymmetrical placement of the sensor wheel pulse plates provides the engine
control module with cylinder specific position ID in conjunction with crankshaft position.

9
M62 TU VANOS CONTROL
As the engine camshafts are rotated by the primary and secondary timing chains, the
ME7.2 control module activates the VANOS solenoids via a PWM (pulse width modulated)
ground signal based on a program map. The program is influenced by engine speed, load,
and engine temperature.
•Shown below: In its inactive or default position, the valves direct 100% engine oil pres-
sure flow to achieve max “retard” VANOS positioning
•Top of next page: As the Pulse Width Modulation (PWM) increases on the control sig-
nal, the valve progressively opens the advance oil port and proportionately closes the
retarded oil port.
Oil pressure pushes the piston toward the advance position. Simultaneously the oil
pressure on the retarded side (rear) of the piston is decreased and directed to the vent
port in the solenoid valve and drains into the cylinder head.
•Bottom of next page: At maximum PWM control, 100% oil flow is directed to the front
surface of the piston pushing it rearward to maximum advance.
Varying the pulse width (on time) of the solenoids control signals proportionately regulates
the oil pressures on each side of the pistons to achieve the desired VANOS advance angle.

11
VANOS SERVICE NOTES
VALVE TIMING PROCEDURES
Refer to TIS for complete Valve Timing Procedures.M62 TU valve timing adjustment is sim-
ilar to the previous non VANOS M62 engine with the exceptionof setting the VANOS
transmissions to their max retard positions with an ohmmeter and attaching the camshaft
gears to each camshaft with single reverse threaded bolts.
• After locking the crankshaft at TDC, the camshaft alignment tools (P/N 90 88 6 112 440)
are placed on the square blocks on the rear of the camshafts locking them in place.
• The exhaust camshaft sprockets and VANOS transmission units with timing chains are
placed onto their respective camshafts.
• The exhaust camshaft sprockets and VANOS transmissions are secured to the
camshafts with their respective single, reverse threaded bolt. Finger tighten only at this
point. Install the chain tensioner into the timing chain case and tension the chain.
• Connect an ohmmeter across two of the three pin contacts on the front edge of one of
the VANOS transmissions. Twist the inner hub of transmission to the left (counter clock-
wise). Make sure the ohmmeter indicates closed circuit. This verifies that the trans-
mission in the default max retard position.
• Using an open end wrench on the camshaft to hold it in place, torque the VANOS trans-
mission center bolt to specification.
CAMSHAFT IMPULSE WHEEL POSITION TOOLS
The camshaft impulse wheels require a special tool set
to position them correctly prior to torquing the retaining
nuts.
The impulse wheels are identical for each cylinder
bank. The alignment hole in each wheel must align
with the tool’s alignment pin. Therefore the tools are
different and must be used specifically for their bank.
The tool rests on the upper edge of the cylinder head
and is held in place by the timing case bolts.
Refer to the TIS repair manual section for complete
information.
BANK I TOOL
BANK I TOOL
BANK II TOOL
ALIGNMENT
IMPULSE