Engine inlet

Rotary slide valve 2

DC adjustment
motor

Supply line to radiator

606_010

Return line from
oil cooler

Rotary slide valve 1
Worm gear

Belt drive
Coolant pump
Return line from heater, turbocharger and transmission
Return line from radiator
39

Engine warm-up and operation is divided into three phases of regulation
Adjustment angle

Warm-up and regulation over 160°

Temperature control range for

After-run over a total of 95°

Warm-up range

After-run range

partial and full load
Switch on engine

Mini-

Static

oil cooler

volume

coolant

stream

s522_107

The following pages describe the engine temperature regulation from the warm-up range, the temperature control
range and finally to the after-run range. This is a highly
simplified representation and does not include the electrical
drive of the Engine Temperature Control Actuator N493 or
the main water pump drive.

40

Temperature regulation sequence

During warm-up, the engine runs through three phases:
• Static coolant
• Mini-volume stream
• Enable engine oil cooler

The different phases are accomplished through the positions
of the rotary valves. The objective is to use the energy generated by the fuel combustion to heat the engine as much as
possible. However, if passenger compartment heating is
required during the "static coolant" phase, heat energy is
provided to the interior.

Turbocharger

Non-return valves

Cylinder head with
integrated exhaust
manifold

Passenger compartment heat exchanger

Cylinder block

After-run Coolant
Pump V51

Climatronic Coolant
Engine oil cooler

Shut-off Valve N422

Rotary valve 2

Rotary valve 1

Coolant pump
Engine Temperature
Control Actuator

Emergency mode

Main radiator

N493

thermostat

s522_092

41

Warm-up with static coolant

To keep the heat from the fuel combustion in the engine,
Rotary valve 2 is closed. This interrupts the coolant flow
from the engine coolant pump to the cylinder block. Rotary
valve 1 blocks return from the engine oil cooler and the
return from the main radiator.
Climatronic Coolant Shut-off Valve N422 interrupts the
coolant flow to the passenger compartment heat exchanger
and Coolant After-run Pump V51 is not activated.

V451
Engine block
N422

Rotary valve 2

Rotary valve 1

Main radiator

s522_092

Warm-up with mini-volume flow
Turbocharger

This control phase in the warm-up range protects the cylinder head and the turbocharger from overheating from the
static coolant in the exhaust manifold.
At a Rotary valve 1 angle position of 145°, Rotary valve 2 is
engaged and begins to open. A small coolant flow begins
through the cylinder block, the cylinder head and the turbocharger returning back to the rotary valve module and
coolant pump.

Rotary valve 2

Rotary valve 1

s522_093
42

Warm-up with mini-volume flow and heating in
the vehicle interior
If heating is required in the passenger compartment during
this phase, N422 opens and After-run Coolant Pump V51
starts delivery. Rotary valve 2 temporarily interrupts the
coolant flow to the cylinder block.

Heat exchanger

The coolant is directed through the cylinder head, turbocharger and heat exchanger. This, however, causes the
warm-up phase of the engine to take longer.
N422 and V51 are also always activated to comply with
requirements in the subsequent control ranges. The coolant
flow to the engine block is reduced or blocked by rotary valve
2 as required.

V451
Engine block
N422

Rotary valve 2

s522_094

Warm-up with map-controled engine active

In this stage, the engine oil cooler is enabled during the
warm-up phase of the engine. Rotary valve 1 moves to a
120° angle position opening the passage to the oil cooler.
Because Rotary valve 2 is still engaged, it also turns more
and enlarges the coolant flow through the cylinder block. A
large amount of heat distribution occurs in the engine block
and excess heat is discharged via the oil cooler.

Engine block

Rotary valve 2
Engine
oil
cooler
Rotary valve 1

s522_095
43

Temperature control range

The innovative thermal management moves seamlessly from
the warm-up range to the temperature control range. Here,
rotary valve module regulation is dynamic and depends on
the engine load.
To conduct excess heat away, the connection to the main
radiator from the rotary valve module is opened. To do this,
positions rotary valve 1 in an angle position of 0° and 85°,
depending on how much heat has to be conducted away. At a
rotary valve 1 angle position of 0° the connection to the
main water cooler is fully opened.

Rotary valve 2

Rotary valve 1

Main radiator

s522_096

If the engine is running at a lower load and speed (partial
load range), the thermal management adjusts the coolant
temperature to 225 °F (107°C). Since the full cooling power
is not required, rotary valve 1 temporarily closes the connection to the main radiator. If the temperature rises above this
threshold value, the connection to the main radiator is
opened again. Constant opening and closing is necessary to
keep the temperature as much as possible at a constant
225 °F (107°C).
When load and engine speed increase, coolant temperature
is reduced to 185 °F (85 °C) (full load range) by first completely opening the connection to the main radiator.

Rotary valve 2

Rotary valve 1

Main radiator
s522_102
44

After-run range when switching off the engine

To prevent the coolant from boiling in the cylinder head and
in the turbocharger when the engine is switched off, the ECM
initiates an after-run function. It can be active for up to 15
minutes after the engine is switched off.
During the after-run function, Rotary valve 1 of N493 is
positioned at an angle between 160 degrees and 255
degrees. The greater the after-run requirement, the higher
the angle position. At 255 degrees of opening angle, the
passage to the return line of the main radiator is fully open
so maximum heat is dissipated.
Rotary valve 2 is in the after-run position and not engaged
with Rotary valve 1. V51 circulates coolant through two
sub-streams in the coolant circuit.

V451

N422

One sub-stream flows over the cylinder head and back to
V51. A second sub-stream flows via the turbocharger
through Rotary valve 1 to the main radiator and also to
After-run Coolant Pump V51.

Rotary valve 2

The cylinder block is not supplied with coolant in the run-on
position.

Rotary valve 1

Main radiator

s522_106

45

Emergency running mode strategy

If the coolant temperature in N493 exceeds 235 °F (113 °C),
the emergency thermostat opens a bypass to the main
radiator. This allows the driver to continue driving the
vehicle to a limited extent if N493 is defective.
If the ECM doesn't receive feedback from N493, it moves
Rotary valve 1 to a maximum engine cooling position regardless of engine load and operating temperature.
If N493 should fail, for example, the electric motor fails or
the rotary valve drive should jam, further measures are
initiated:

•

V451

A fault message is displayed in the instrument cluster
and at the same time engine speed is limited to 4000
rpm. A warning tone is issued and the EPC is illuminated.

•

The actual engine coolant temperature is also displayed
in the instrument cluster.

•

Climatronic Coolant Shut-off Valve N422 is opened.

•

After-run Coolant Pump V51 is activated to ensure
cylinder head cooling.

•

A DTC is logged in the Engine Control Module.

If the rotary valve position sensor signal is implausible or the
sensor fails, the ECM activates Rotary valve 1 to a maximum
cooling position as a failsafe.

N422

Rotary valve 2

Rotary valve 1

Emergency mode thermostat
s522_097

Vehicles with DSG transmissions
On vehicles with DSG transmissions, the coolant circuit is
expanded to include a transmission heat exchanger and
Transmission Coolant Valve N488.

Gear oil cooler
Auxiliary radiator
Coolant shut-off valve N82
s522_101
46

Functional diagram of Engine Temperature Control Actuator N493
Connections
1

Sensor ground (connection in engine wiring harness)

2

Sensor signal

3

Sensor + (5 V connection in engine wiring loom)

4

Actuator –

5

Actuator +

2

3

4

5

1

606_021

Transmission Coolant Valve N488
N488 controls the flow of warm coolant from the engine to
the transmission gear oil cooler.

It is held open by mechanical spring force when not activated and closes when the engine is started. The coolant
flow to the transmission opens at a coolant temperature of
176 °F (80 °C) and closes again at 194 °F (90 °C). This helps
the manual transmission to attain its optimal friction
temperature.

When required, the solenoid valve is activated by the ECM.

Electrical connection

Coolant flow to the engine

Solenoid coil

606_022

Piston

Coolant flow
to the cooler

47

Coolant Recirculation Pump V50
This pump is used as a circulation pump for the passenger
compartment heat exchanger in vehicles with longitudinally
mounted engines. It is activated by Climatronic Control
Module J255 via a PMW signal. It is diagnosed through J255.
Function
Coolant Recirculation Pump V50 is activated when the ignition is switched on depending on the coolant temperature
and the desired interior temperature setting of Climatronic
Control Module J255.
When V50 is running, coolant is circulated between the
engine and the passenger compartment heat exchanger.

Climatronic Coolant Shut-off Valve N422

Coolant Recirculation Pump V50

606_056

N422 is installed on longitudinally mounted engines. The
valve permits or prevents coolant flow to the passenger
compartment heat exchanger. See page 35, figure 606_023.
Function
Climatronic Coolant Shut-off Valve N422 is identical to
Transmission Coolant Shut-off Valve N488 (see previous page).
It is open (allowing coolant flow) when it is not energized and
closes (preventing coolant flow) when current is applied.
It is opened by spring force and closes when the engine is
started.
The valve opens when the heating, run-on cooling and
start-stop functions are activated. N422 is controlled by
Climatronic Control Module J255 and requires adaptation using
the VAS Scan Tool.

Coolant After-run Pump V51

Coolant Shut-off Valve N82

V51 is installed on vehicles with transversely mounted
engines. It is identical to Coolant Recirculation Pump V50
used in vehicles with longitudinally mounted engines. It is
activated by the ECM with a PWM signal after receiving a
request from Climatronic Control Module J255.

Coolant Shut-off Valve N82 is activated by the Engine Control
Module.

V51 also assists the engine coolant pump to increase coolant
flow through the passenger compartment heat exchanger at
defined engine speeds thus providing higher heating output.
It also helps reduce turbocharger temperature more quickly
which helps extend engine oil life.

48

Depending on the requested temperature in the passenger
compartment, N82 shuts off the coolant flow through the
passenger compartment heat exchanger. This is done for
example, to heat up the engine.

Air supply and charging
System overview

C
A

B

D

E

V465

N249

F

G31

Exhaust gases

N316
J338
G186
G187
G188

G

Intake air (vacuum)
Charge air (charge pressure)

G336

Wastegate (charge pressure)
606_025

G42 with G71

Key:
A

Exhaust flow

G31

Charge Air Pressure Sensor

B

Exhaust turbocharger

G42

Intake Air Temperature Sensor

C

Air filter

G71

Manifold Absolute Pressure Sensor

D

Fresh air flow

G186 EPC Throttle Drive

E

Wastegate valve

G187 EPC Throttle Drive Angle Sensor 1

F

Charge air cooler

G188 EPC Throttle Drive Angle Sensor 2

G

Intake manifold flaps

G336 Intake Manifold Runner Position Sensor
J338 Throttle Valve Control Module
N249 Turbocharger Recirculation Valve
N316 Intake Manifold Runner Control Valve
V465 Charge Pressure Actuator

Note
The Charge Pressure Actuator V465 must be replaced after removing the lock nut from the linkage.
After replacement, the charge pressure actuator must be adapted using the Scan Tool.
49

Air routing system for transversely mounted engines

Turbocharger (B)

Turbocharger Recirculation
Valve N249

Air filter
(C)

Charge Pressure Actuator
V465

606_037

Intake manifold

Charge air cooler
(F)
Intake Manifold Runner Control Valve
N316

Intake Manifold
Runner Position
Sensor G336

Air intake
(D)

Intake Air Temperature Sensor G42 with
Manifold Absolute Pressure Sensor G71
Throttle Valve Control Module J338