2005 BMW 745i N62B44 Engine Workshop Manual

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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.
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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.

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N62 Engine
The coolant flows to the rear of the engine block, from there through the side channels to
the cylinder walls and then into the cylinder heads (lower left picture). The cast aluminum
cover at the rear of the engine block (with sealing bead) is shown on the lower right.
Water Pump/Thermostat Housing
The water pump is combined with the thermostat housing and is bolted to the timing case
lower section.
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The impeller is made from reinforced plastic.
42-02-59
Water Pump / Thermostat Housing
1. Map-controlled themostat (radiator cool return flow).
2. Electrical connection for Thermostat Heating element.
3. Thermostat Mixing Chamber
4. Temperature Sensor (hot coolant from engine)
5. Radiator in-flow (hot coolant from engine)
6. Heat exchanger (transmission oil return flow)
7. Leakage Chamber (evaporation space)
8. Alternator in-flow (cool supply)
9. Water Pump
10. Expansion Tank Connection

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N62 Engine
Leakage Restraint System in the Water Pump
The water pump has a leakage restraint system for the functional leakage from the pump
shaft piston ring type seal. The coolant which escapes through the pump shaft sliding ring
seal usually accumulates and evaporates through a hold in the leakage chamber (evapora-
tion area).
If the sliding ring seal is faulty, the leakage chamber fills
completely with coolant. Sliding ring seal leakages can
be detected by monitoring the fluid level in the leakage
chamber (inspection hole).
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In the past, fully functional water pumps were often replaced because the functional
sliding ring seal leakage which is necessary for water pump operation resulted in evapora-
tion residues being left on the external walls of the water pump.
The leakage restraint system has the advantage in that the coolant escaping from the slid-
ing ring seal (normal, functional leakage) evaporates without a trace and cannot be mis-
takenly identified as a water pump defect during visual inspections.
Timing Chain Cover Lower Section
The waterpump mounts to the lower section to
channel coolant to the engine block.
42-02-61 Water Pump
1. Impeller
2. Sliding Ring Seal
3. Leakage Chamber / Evaporation Space
4. Leakage Chamber Cover
5. Delivery from the sliding ring seal to the leakage chamber
6. Hub of pulley and viscous clutch
Timing Chain Cover Lower Section
1. Coolant to Engine
2. Rear Water Pump Housing in Lower Section
3. Mount for Drive Belt Tensioner Pulley
4. Crankshaft Radial Seal
42-02-62

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N62 Engine
Map-controlled Thermostat
The map-controlled thermostat allows the engine to be cooled relevant to operating con-
ditions. This reduces fuel consumption by approximately 1-6%. The electrical connections,
the design and the map-controlled thermostat response have been enhanced. The map-
controlled thermostat function is the same as previous engines (M62).
Cooling Module
The cooling module contains the following main cooling system components:
• Cooling radiator
• Air conditioning condenser
• Transmission oil/water heat exchanger
• Hydraulic fluid radiator
• Engine oil radiator
• Main electric fan
• Fan shroud for viscous coupling fan
All the components (with the exception of the transmission oil radiator) can be removed for
repairs without disassembling any other coolant circuit. All connections have been fitted
with the quick-release coupling which are used in current models.
Maped-Controlled Thermostat
1. Radiator Return Flow To Thermostat
2. Connection for Thermostat Heating Element
3. Temperature Sensor
4. Radiator in-flow (hot coolant from engine)

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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).
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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

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N62 Engine
Transmission Oil/Coolant Heat Exchanger
The transmission oil/coolant heat exchanger ensures that the transmission oil is heated up
quickly and also that it is appropriately cooled. When the engine is cold, the transmission
oil/coolant heat exchanger thermostat switches into the engine's recirculated coolant cir-
cuit. This allows the transmission oil to heat up as quickly as possible (with the engine
coolant).
When the return flow water temperature reaches 82 ºC, the thermostat switches the trans-
mission oil/coolant heat exchanger to the low-temperature coolant radiator circuit (refer to
the cooling circuit diagram) to cool the transmission oil.
Electrically Operated Fan
The electric fan is integrated in the cooling module and is mounted directly in front of the
radiator. The speed is regulated by the ECM.
Viscous Coupling Fan
The viscous coupling fan is driven by the water pump. The noise output and the perfor-
mance of the fan coupling and the fan wheel have been optimized as compared with the
E38M62. The viscous coupling fan is used as the final level of cooling and switches on at
an air temperature of 92 ºC.
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N62 Engine
Engine Block
Oil Sump
The oil sump consists of two parts. The upper section of the oil sump is made from cast
aluminum and is sealed to the crankcase with a rubber-coated sheet steel gasket. This
section of the oil sump has a cross shaped cut out oil filter element recess. The upper sec-
tion of the oil sump is inter connected to the oil pump and is sealed with a sealing ring. The
double panel (noise insulation) lower section of the oil sump is flanged to the upper section
of the oil sump.
Crankcase
The crankcase has a one-piece “open deck” design and is made entirely from AluSil. The
cylinder walls are hardened using a specific procedure (exposure honing). Exposure hon-
ing involves treating the cylinders with a special “soft stripping”. This removes the aluminum
from the cylinder surface and the hard silicone particles remain.
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1. Flow to engine “V” (return coolant collection area) 2. External cylinder bank wall
Oil Sump Components
1. Upper Section of The Oil Sump
2. Oil Pump
3. Oil Level / Condition Sensor
4. Lower Section of The Oil Sump
5. Oil Filter Housing
6. Oil Drain Plug
42-03-65
42-03-66 42-02-67

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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