coolant temperature BMW 645Ci COUPE 2002 E63 N62B44 Engine Workshop Manual

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The electrically-operated secondary air pump is mounted to the vehicle body. The pump
draws out filtered fresh air from the air cleaner housing during the warm-up phase and sup-
plies it to the two secondary air Non-return Valves.
Once the engine has been started, the secondary air pump is supplied with voltage by the
ECM via the secondary air pump relay. It remains switched on until the engine has taken in
a certain amount of air.
The O ON
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period may be a maximum of 90 seconds and it depends on the following engine
operating conditions:
• Coolant temperature (from -10 ºC to approximately 60 ºC)
• Air temperature (NTC sensor in HFM)
• Engine speed
One non-return valve is mounted on each cylinder head (see also Engine Views).
The non-return valves are opened by the pressure generated from the secondary air pump.
The secondary air is led through a pipe to the secondary air ducts (integral in the cylinder
heads) for distribution into the exhaust ports.
The non-return valves are sprung closed when the secondary air pump is deactivated. This
prevents exhaust vapors, pressure and condensation from flowing back into the secondary
air pump.
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N62 Engine
43-02-14
View From Rear of The Cylinder Head
1. Cylinder Head Lead
2. Non-return Valve (SLV)
3. Secondary Air Pump Connection

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N62 Engine
Cooling System
Coolant Circuit - 14 Liter Coolant Capacity
42-02-56
Cooling System (Circuit Flow)
1. Cylinder Head Bank 5-8 12. Radiator
2. Coolant Supply (heater core) 13. Radiator Partition (low temp section)
3. Water valve with electric water pump 14. Temperature Sensor
4. Cylinder Head Gasket 15. Water Pump
5. Coolant Supply Line 16. Radiator Return Flow
6. Cylinder Head Ventilation Lines 17. Radiator Ventilation Line
7. Hole (crankcase venting system) 18. Expansion Tank
8. Transmission oil lines 19. Thermostat
9. Oil/water heater exchanger for automatic transmission 20. Cylinder Head Bank 1-4
10. Thermostat for transmission oil heat exchanger 21. Vehicle Heater
11. Alternator Housing 22. Radiator (High Temperature Area)

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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
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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