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Technical Service Bulletin Transaction No.: 2074303/11
19 Engine: cooling system - red coolant temperature/coolant level warning lamp on - .
4.0 ltr. V8 TESI Release date: Apr 14, 2026
Condition
Model(s) VIN Range Vehicle Specific Equipment
$8, SQ7, and SQ8 | 2020 - 2025
2020 — 2023 All 4.0 Itr. V8 TFSI
RS Q8
2025

RS6 Avant, and RS 7 | 2021 - 2025

REVISION HISTORY

Irevion [ote [ounces

11 Revised header (updated model years)

Revised Production Solution (Updated verbiage)

08/19/2025 | Revised header (updated model years)

» | 06/27/2025 | Revised Service (Updated documentation instructions)

Customer states:

+ The red coolant warning lamp lights up:

- Switch off the engine and check the coolant level.
— Coolant temperature: too high. Let engine run with the vehicle stationery.

Workshop findings:

* Coolant level in coolant expansion tank is too low

+ Coolant loss at the front end of the engine.

+ The engine is overheating.

Documentation required

Technical Background
EA825 V8 TFSI engines across all power classes are currently equipped with a switchable mechanical coolant
pump.
It is activated via the electric changeover valve N649.
When N649 is activated, it switches a vacuum to the mechanical coolant pump. This pushes a locking sleeve over
the pump impeller, which can cause coolant to stagnate.
When N649 is not activated, no vacuum is switched to the mechanical coolant pump, and the coolant pump is not
covered. In this case, the coolant is pumped through the coolant pump impeller.
The charge pressure control for the EA825 V8 TFSI turbochargers is electropneumatic.
This means that charge pressure positioners V465 and V546 are electropneumatic pressure converters. Depending
on activation (PWM) by the engine control unit, they can induce a calculated negative pressure (characteristic
curve). This determines the opening path of the wastegate. They are open when they are not activated.
SSP 676 contains more information on the EA825 V8 TFSI engine cooling system.
Production Solution
Optimized coolant pumps from the following vehicle production date onwards:

+ — A8 from vehicle production date 02/11/2026

+ §8 from vehicle production date 02/17/2026

+ $Q7, SQ8 and RS Q8 from vehicle production date 02/12/2026
Service
Step1
Check whether there is a visible external leak in the area surrounding the mechanical coolant pump.

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Please refer to the attachment “Overview of coolant distributors” and the following two images.

2 Map Controlled Engine
Cooling Thermostat
= F265
7—
we _—
y Coolant distribution
xX y \ iv module
> ee
s Py \_P
) — ” /
» : ‘ =
7 x) ye J
al - A = e
q i.
AA Ay
f >
Gasket
Coolant pump/vacuum
regulating assembly
Figure 1. Coolant distribution
a Coolant distributor
WP Se
. a
\ ame
,)<— —_ Leakage reservoir for mechanical
iy a) coolant pump
Rv
~)y
Figure 2. Coolant distributor and leakage reservoir
A fresh coolant leak around the mechanical coolant pump can take the form of fresh drops on the underside of the
coolant distributor or the leakage reservoir (See figures 1 and 2 or attachment “Overview of coolant distributors”). If
necessary, perform a pressure test of the cooling system according to ELSA.

_ =

ens.

2! 4 wm NN Sa

: ee + ga Nee Pp
Se - = a. a4
3 SS ot —s—
St EE Se
mr 5 -B34638239-85-4- as

Figure 3. Modulating piston moved back correctly (starting position, not actuated)

+ The modulating piston (orifice panel) must completely cover the pump impeller when a vacuum (maximum:
~600mbar) is applied at the vacuum connection of the mechanical coolant pump. The vacuum must be
maintained throughout the functional test.

# = «=:
ee oe
— ‘
~ aH — 8
a a
__- 90 eee | —_——
Pa eo — ls Sane
~— — - é athe '
: . ae Se age
Figure 4. Modulating piston correctly deployed (end position, actuated)

Note: The modulating piston tilting while it is moving out is not a reason for complaint if the end
positions (as pictured above) are reached correctly.
If the end positions are not reached correctly, replace the mechanical coolant pump.
14 cee)
ee!
2 a
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A
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ey SE FN
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12 Nile ba. Sey a
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a x VA SS
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16
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Figure 5. Assembly overview — coolant pump/thermostat incl. switchable mechanical coolant pump, number 12.
When billing, please always attach a photo that clearly shows the complaint to DOC-IT. To ensure a reference to the
vehicle, the photo must:
+ Include the VIN and date.
+ Must not be edited.
+ Should be in focus and taken with sufficient light.

If appropriate, please mark the location of the problem so that parts analysis has a clear reference to the complaint.
Please ensure that the photo documentation does not show any people and/or face, license plates, or customer
data.
Warranty
Claim Type: + If the vehicle is outside of any warranty, this Technical Service Bulletin is informational
only.
Service Number: Case 1: If a coolant leak was detected at the mechanical coolant pump (to outside or into
vacuum chamber). Use service number: 1950
Case 2: If a deviation was detected in the switching function of the mechanical coolant
pump. Use service number 1950.
Case 3: If only the switch valve for mechanical coolant pump N649 has been replaced (and
not the mechanical coolant pump). Use service number 1985
Damage Code: Case 1: 050
Case 2: 017
Case 3: 010
Labor Operations: | Remove and install noise insulation 1082 1900 | See SRT with
associated operations
Check and top off coolant 1938 3599 |10 TU
Check cooling system — pressure test 1901 0150 |See SRT with
associated operations
Check coolant pump 1950 0299 |20TU
Remove and install valve N649 1984 19xx |See SRT with
associated operations
Remove and install coolant pump (if necessary) 1950 19xx | See SRT with
associated operations
Charge battery 2706 8950 |See SRT with
associated operations
GFF 0150 0060 | Labor according to the
diagnostic log
Claim Comment: As per TSB 2074303/11
All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures
Manual. Claims are subject to review or audit by Audi Warranty.
Additional Information
All part and service references provided in this TSB (2074303) are subject to change and/or removal. Always check
with your Parts Department and/or ETKA for the latest information and parts bulletins. Please check the Repair
Manual for fasteners, bolts, nuts, and screws that require replacement during the repair.
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