2002 BMW 745i valve

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N62 Engine
Coolant Circuit
The coolant flow has been optimized allowing the engine to warm up as quickly as possi-
ble after a cold start as well as even and sufficient engine cooling while the engine is run-
ning. The cylinder heads are supplied with coolant in a cross-flow pattern. This ensures
more even temperature distribution to all cylinders. The cooling system ventilation has been
improved and is enhanced by using ventilation ports in the cylinder heads and in the radi-
ator. The air in the cooling system accumulates in the expansion tank. When a pressure of
2 bar is reached in the expansion tank, the air is bled out by the pressure relief valve in the
reservoir cap.
N No
ot
te
e:
:
The ventilation ports in the front of the cylinder heads provide quicker “self bleeding”
during a routine coolant exchange. The complex cooling system and the small ventilation
ports require that time should be allowed after the cooling system has been filled for the air
to escape.
Coolant flow in the Engine Block
The coolant flows from the water pump through the feed pipe (1) in the engine's V and to
the rear of the engine block. This area has a cast aluminum cover (see following illustration).
From the rear of the engine, the coolant flows to the external cylinder walls and from there
into the cylinder heads.
The coolant then flows from the cylinder heads into the engine block V and through the
return connection (3) to the thermostat housing. When the coolant is cold it flows from the
thermostat (closed) directly into the water pump and back to the engine (recirculating for
faster warm up).
When the engine reaches operating tempera-
ture (85 ºC-110 ºC), the thermostat opens the
entire cooling circuit to include the radiator.
42-02-57
Engine Block Coolant Flow
1. Coolant from the water pump through the feed pipe
to the rear of the engine.
2. Coolant from the cylinder walls to the thermostat
housing.
3. Return connection to water pump/thermostat.

Downloaded from www.Manualslib.com manuals search engine 43
N62 Engine
Cooling Radiator
The radiator is made from aluminum and is divided into a high-temperature section and a
low-temperature section by a partition wall (see coolant circuit diagram). The coolant first
flows into the high-temperature section and then back to the engine, cooled.
Some of the coolant flows through an opening in the radiator partition wall to the low-tem-
perature section where it is cooled further. The coolant then flows from the low-tempera-
ture section (when the ÖWT thermostat is open) into the oil/coolant heat exchanger.
Coolant Expansion Tank
The expansion tank is mounted on the right hand wheel housing (engine compartment).
N No
ot
te
e:
:
The expansion tank should never be filled above the Max marking. Excess coolant is
expelled by the pressure relief valve in the cap as it heats up. Avoid overfilling the expan-
sion tank because the cooling circuit design ensures very good “self bleeding”.
Cooling Components
1. Cooling Radiator 4. Engine oil/air heat exchanger connection
2. Expansion Tank (hot countries only)
3. Water Pump 5. Transmission oil/coolant heat exchanger

Downloaded from www.Manualslib.com manuals search engine 46
N62 Engine
Crankshaft
The N62 uses an inductively hardened cast-iron crankshaft. The crankshaft has five main
bearings (familiar 4 bolt cast iron caps) and is hollowed around bearing journals 2, 3, and
4 for weight reduction. The fifth bearing is also the “thrust” bearing.
The crankshaft stroke for the B44
is 82.7 mm.
Crankshaft Thrust Bearing
The thrust bearing halves are multiple pieces that are assem-
bled as one part for the the number five main bearing at the
rear of the engine. The bearing thickness conforms to the
familiar triple classification system (yellow - green - white).
Piston and Connecting Rod
The reduced weight cast piston contains integrated
valve reliefs in the piston crown. The pistons are made
from high-temperature aluminum alloy equipped with
three piston rings.
• First piston ring groove = square ring
• Second piston ring groove = taperface ring
• Third piston ring groove = three-part oil control ring
The forged steel connecting rod and cap is separated
by the familiar “cracked” process. The connecting rod
(large end) is angled at 30º allowing sufficient articula-
tion in a very compact space. The pistons are cooled
by oil jets spraying under the exhaust side of the pis-
ton crown.
Crankshaft
1. Crankshaft Sprocket
2-4. Hollowed Area (Weight Reduction)
42-02-68
42-02-70
42-03-70

Downloaded from www.Manualslib.com manuals search engine 48
N62 Engine
Lubrication System
Crankcase with oil jets
The engine oil is supplied by the oil pump to the lubrication points in the engine block and
is pumped into the cylinder heads. The following components in the crankcase and cylin-
der head are supplied with engine oil:
C Cr
ra
an
nk
kc
ca
as
se
e
• Crankshaft bearings
• Oil jets for piston cooling
• Oil jet for the drive chain (bank 5-8)
• Tensioning rail for drive chain (bank 1-4)
Oil Check Valves
Three oil check valves are inserted into each cylinder head from the outside. This prevents
the engine oil from draining out of the cylinder head and the VANOS units.
T Th
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c
ch
he
ec
ck
k
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;
c
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.
C Cy
yl
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nd
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r
h
he
ea
ad
d
• Chain tensioner
• Guide rail on cylinder head
• Hydraulic valve adjustment elements (HVA)
• VANOS supply
• Camshaft bearings
• Overhead oil tubes for the valve gear
42-02-71 Crankcase with Oil Jets
1. Oil Jet for Drive Chain Cylinder Bank 5-8
2. Oil Jets for Piston Cooling
42-02-72
Oil Check Valves
1. Oil Check Valve for VANOS Intake
2. Oil Check Valve for VANOS Exhaust
3. Oil Check Valve for Cylinder Head Oil Supply

Downloaded from www.Manualslib.com manuals search engine 49
N62 Engine
N No
ot
te
e:
:
T
Th
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o
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.
Oil Pressure Switch
The oil pressure switch is located on the side in the bank 1-4 cylinder head.
Oil Pump
The oil pump is mounted at an angle to the crankshaft bearing cap and is driven by the
crankshaft using a roller chain. The oil pump is a two-stage gear oil pump with two paral-
lel switched gear clusters.
The two pair of gear clusters are stacked one
behind the other and work in two stages.
Stage two (both pump supply circuits) is only
active in the lower engine speed range up to
approx. 2,000 rpm to provide sufficient oil pres-
sure for the VANOS at high oil temperatures.
Stage two is deactivated hydraulically at a pres-
sure of 2 bar.
42-02-73
42-02-75
42-02-76 Oil Pump
1. Drive Shaft
2. Mounting Points
3. Oil Filter
4. Pressure Relief Valve (over 15 Bar)
5. Control Valve (Pump Stage/Pressure Control)
6. Oil supply from the oil pump to the engine
7. Oil pressure control tube from the engine to
the control valve.

Downloaded from www.Manualslib.com manuals search engine 50
N62 Engine
Oil Pressure Control
O Oi
il
l
p
pr
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su
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c
co
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p po
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it
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.

S St
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a ab
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2
2
b
ba
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,
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o op
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s su
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.

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=
=
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p
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su
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c
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it
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s
a ac
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ti
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d
w
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it
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.

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)
t
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.
Oil Pressure Control
1. Oil Pump Stage 1 5. Sealing Plug
2. Oil Pump Stage 2 6. Oil Pump Housing
3. Pressure Control Valve Piston 7. Oil Sump
4. Pressure Control Valve Spring

Downloaded from www.Manualslib.com manuals search engine 51
N62 Engine
Oil Filter
The canister type oil filter (3) is located under the
engine by the oil sump. The support for the oil
filter is integrated in the rear oil pump cover.
The oil filter housing (2 with o-ring) is threaded
into the rear of the oil pump cover through an
opening in the oil sump.
A A
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f
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a
as
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se
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-
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ng
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i
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ve
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d
(
(1
1
w
wi
it
th
h
o
o-
-r
ri
in
ng
g)
).
.
The filter element support dome contains an over pressure relief valve. If the filter element
is blocked, this valve bypasses unfiltered engine oil around the element to the supply lubri-
cation to the engine.
Pressure Control
The oil pressure control valve in the oil pump has two functions:
1. Deactivates stage two oil pump circuit above 2 bar. Stage two is only active in the
lower speed range. This is to ensure that there is always sufficient oil pressure for
the VANOS units even at high oil temperatures and low speeds. The oil pump power
consumption is reduced by deactivating stage two.
2. Monitoring the required oil pressure for the engine. The piston in the control valve is
moved by a spring against the engine control pressure which is returning from the
engine. This means that precise monitoring of the actual engine oil pressure is pos-
sible.
A A
s
se
ep
pa
ar
ra
at
te
e
p
pr
re
es
ss
su
ur
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r
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el
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ie
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f
v
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th
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o
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p
pu
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mp
p
a
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to
om
ma
at
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ly
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o
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s
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at
t
t
th
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e
m
ma
ax
xi
im
mu
um
m
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s-
-
s su
ur
re
e
o
of
f
a
ap
pp
pr
ro
ox
xi
im
ma
at
te
el
ly
y
1
15
5
b
ba
ar
r.
.
T
Th
hi
is
s
p
pr
re
ev
ve
en
nt
ts
s
d
da
am
ma
ag
ge
e
i
in
n
t
th
he
e
o
oi
il
l
p
pu
um
mp
p
e
es
sp
pe
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ci
ia
al
ll
ly
y
a
at
t
l
lo
ow
w
o
oi
il
l
t te
em
mp
pe
er
ra
at
tu
ur
re
es
s.
.
42-02-77

Downloaded from www.Manualslib.com manuals search engine 53
N62 Engine
Review Questions
1. What is the function of the throttle valve?
2. What are the conditions that will result in stage two oil supply?
3. What does the term “cracked” connecting rod mean?
4. What does the low temperature area refer to in the cooling system?
5. What is the difference between the left and right drive chain tensioning assemblies?
6. How is the funnel adjustment made on the 5-8 Variable intake manifold if only one
actuating motor is used?
7. What is minimum and maximum valve lift provided by the Valvetronic system?
8. What is chamber A and chamber B used for in the Bi-VANOS system?
9. What retains the initial VANOS sprocket to hub position when oil pressure is not pre-
sent?
10. How should the drive belt be removed?