acceleration), Oil Pressure Regulation Valve N428 is deenergized by the ECM which in turn vents the active oil
passage. The force of the remaining surface under oil
pressure is less than the force of the control piston spring
and closes the oil passage to the control surface of the
adjustment ring.

Support bracket
Control surface

Without oil pressure, the control spring swivels the adjustment ring clockwise around the center bearing. The adjustment ring now swivels out of its center position and
increases the delivery space between the individual vanes
which increases oil delivery. The higher volumetric oil flow
is countered by the size of the oil galleries and crankshaft
bearing play causing the oil presssure to increase.
If communication with the ECM is lost, spring force will
move the control surface to the high delivery position. This
ensures that the engine components are protected.

608_027

Control piston spring

Control piston

Active oil passage

N428

Control edge

Oil pan

Non-return valve

Oil pressure from the oil gallery

608_056

Note

The maximum rate of delivery is always available when the solenoid valve is de-engerized.
27

Oil filter module
The oil filter module consists of the oil cooler, which is
mounted to the side of the oil filter module, as well as the
oil filter bypass valve and oil cooler bypass valve.

Depending on the engine’s installation position, there are
two different oil filter modules.

Longitudinally mounted engines
Components:
• Upright oil filter housing with oil drain valve
• Filter cartridge
• Reduced Oil Pressure Switch F378 (0.3 – 0.6 bar)
• Oil Pressure Switch F22 (2.5 – 3.2 bar)

Filter cartridge

Coolant return line
from the oil cooler

Oil Pressure
Switch F22

Oil return line
to the engine lubrication points

Reduced Oil
Pressure Switch F378

Coolant feed line
to the oil cooler

Oil cooler

Oil feed line
from the oil pump

608_045
28

Transversely mounted engines
•
•
•
•

Upright oil filter housing with oil drain valve
Filter cartridge
Reduced Oil Pressure Switch F378 (0.3 – 0.6 bar)
Oil Pressure Switch F22 (2.5 – 3.2 bar)

Oil cooler

Coolant return line
from the oil cooler

Oil Pressure
Switch F22
Oil filter bypass valve
Oil return line
to the engine lubrication points
Reduced Oil Pressure
Switch F378

Coolant feed line
to the oil cooler

Filter cartridge

Oil feed line
from the oil pump

608_046

29

Cooling system
Thermal management
Cylinder head coolant valve
N489

The EA288 diesel engine uses a thermal management strategy designed to shorten the warm-up phase after a cold start
and implement emission reduction measures quickly.
The thermal management system also directs the heat produced by the engine during normal operation to where it can
be advantageously used to boost vehicle efficiency. A main
focus is to reduce intra-engine friction.
The overall cooling circuit has three sub-circuits:
• Secondary cooling circuit (micro circuit)
• Cylinder head
• EGR cooler of low pressure exhaust gas recirculation
system
• Passenger compartment heat exchanger
• Electrical auxiliary coolant pump
• Primary cooling circuit (high temperature circuit)
• Cylinder block and intake manifold
• Engine and transmission oil cooler
• Coolant thermostat (3/2-way valve)
• Main vehicle radiator
• Switchable coolant pump

608_018

Coolant pump

• Cooling circuit with charge air cooler (low temperature
circuit)
• Charge air cooler
• Charge air cooler (in front of vehicle) radiator
• Charge Air Coolant Pump V188

Switchable coolant pump
A switchable coolant pump is used in the thermal management system 2.0L TDI engine. This coolant pump can be
switched on and off, allowing coolant circulation to be
stopped when the engine is cold. Static coolant heats up
more quickly and can bring the engine to operating temperature more effectively.
A hydraulically actuated control valve activated by Cylinder
Head Coolant Valve N489 slides over the rotating impeller
and prevents the coolant from circulating.

Impeller with integrated
wobble plate

Drive shaft
Cylinder Head
Coolant Valve
N489

Annular piston

Control valve
Bearing

Pump casing

Axial-piston pump
Guide bushing with
coolant ducts
Annular piston ring seals

Compression spring for resetting
the control valve
608_029

Control valve seal

30

Coolant pump function
The control valve can slide over the impeller which will
prevent coolant from being circulated. The impeller has an
integral cast stainless steel plate that functions as a
wobble plate. An axial piston pump integrated in the pump
housing is actuated by the wobble plate. The pump recirculates the coolant to the coolant circuit via Cylinder Head
Coolant Valve N489.

Static coolant

Cylinder Head Coolant Valve N489
ON

Control valve slid
over the impeller
Axial-piston pump

When N489 is energized, the return port to the coolant
circuit closes. This happens because the lifting motion of
the axial piston pump produces a hydraulic pressure at the
annular piston. The control valve slides over the impeller
against spring tension and seals the impeller off from the
cylinder block. No coolant is circulated.

Impeller

Wobble plate with
race for axial piston
pump

608_039

Annular piston displaced

Coolant is circulated
If N489 is de-energized, the return port to the coolant
circuit opens, the ring-shaped piston is pushed back by the
compression spring and restores the control valve to its
original position.
The impeller is uncovered and the coolant begins to circulate. The axial piston pump operates whenever the engine
is running.

Cylinder Head Coolant Valve N489
OFF

Control valve retracted

Return port
open

Coolant Pump Operation 1

Coolant Pump Operation 2
608_007
31

System overview
The following diagrams show the cooling system in the engine
version which meets the EU5 exhaust emission standard.

1

2

3

5
4

6
8

7

10

9

11
16

12

17

13

14

15

18

608_073

Key:
1
2
3
4
5
6
7
8
9

Coolant expansion tank
Passenger compartment heat exchanger
Auxiliary heater (not for the North American market)
Recirculation Pump V55
Heater Support Pump V488
Engine Coolant Temperature Sensor G62
Coolant connection
EGR cooler
Cylinder Head Coolant Valve N489 (mounted on
water pump)

10
11
12
13
14
15
16
17
18

Coolant thermostat
Throttle valve
Engine oil cooler
Coolant Fan V7
Coolant Fan 2 V177
Radiator
Charge Air Cooling Pump V188
Charge air cooler integrated in intake manifold
Heat exchanger for charge air cooling

Cooled coolant
Heated coolant
32

Secondary cooling circuit (micro circuit, heating circuit)
When the engine is cold, the thermal management system
operates the cooling system in the secondary cooling circuit
mode. This ensures the engine and passenger compartment are heated quickly.

V488 provides back-up in cold ambient conditions to ensure
that a minimum volumetric flow is achieved at high coolant
viscosity.
The driver’s temperature preference is registered by the A/C
control module when V488 is activated.

Cylinder Head Coolant Valve N489 is energized and the
water pump control valve is moved to cover the impeller to
prevent coolant flow in the engine block.
At the same time, Heater Support Pump V488 operates.
Coolant flows in the secondary cooling circuit in a controlled manner depending on the coolant temperature in
the cylinder head.

1

2

3

5

4

6
8

7

10

9

11
16

12

17

13

18

14

15
608_074

33

Secondary cooling circuit – engine cooling requirements / high engine load
The switchable coolant pump is activated (N489 de-energized) at increasing engine load and engine speed. This
ensures the engine is cooled. After the engine speed drops
below a threshold level, the coolant pump is de-activated
again (N489 energized) and the engine is operated without
coolant circulation until a required temperature is achieved.

1

The coolant pump is continuously activated when the
coolant temperature exceeds a threshold level at the cylinder head, indicating that the engine is at operating temperature. When the coolant pump is activated, it is ensured
that a sufficient quantity of coolant flows through the
cylinder head. For this purpose, the engine thermostat has
its own integrated by-pass (short circuit). (refer to p. 37).

2

3

5

4

6
8

7

10

9

11
16

12

17

13

14

15

18

608_075

Key:
1
2
3
4
5
6
7
8
9

Coolant expansion tank
Passenger compartment heat exchanger
Auxiliary heater (not for the North American market)
Recirculation Pump V55
Heater Support Pump V488
Engine Coolant Temperature Sensor G62
Coolant connection
EGR cooler
Cylinder Head Coolant Valve N489 (mounted on
water pump)

10
11
12
13
14
15
16
17
18

Coolant thermostat
Throttle valve
Engine oil cooler
Coolant Fan V7
Coolant Fan 2 V177
Radiator
Charge Air Cooling Pump V188
Charge air cooler integrated in intake manifold
Heat exchanger for charge air cooling
Cooled coolant
Heated coolant

34

Primary cooling circuit (high temperature circuit) – coolant at operating temperature
If the coolant is at operating temperature, the coolant
thermostat opens and enters control mode. The radiator
(main radiator) is integrated in the cooling circuit.

1

The coolant thermostat controls the engine outlet temperature and is located in the main radiator feed line.

2

3

5

4

6
8

7

10

9

11
16

12

17

13

18

14

15
608_076

35

Low temperature cooling circuit – coolant circuit for charge air cooling
temperature is regulated by activating Charge Air Cooling
Pump V188.

The intake manifold temperature is used as a reference
variable for activating the charge air cooling circuit. After
this targert temperature is achieved, the intake manifold

1

2

3

5

4

6
8

7

10

9

11
16

12

17

13

14

15

18

608_077

Key:
1
2
3
4
5
6
7
8
9

Coolant expansion tank
Passenger compartment heat exchanger
Auxiliary heater (not for the North American market)
Recirculation Pump V55
Heater Support Pump V488
Engine Coolant Temperature Sensor G62