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Technical Service Bulletin
. 19 Engine: cooling system - red coolant temperature/coolant level warning lamp on - 4.0 Itr. V8
Topic TFSI
United States 444 Volkswagen of America, Inc. (6444)
Transaction
[Status | Released for publishing
Release date Aug 19, 2025
New customer code
Object of complaint Complaint type [Position]
engine -> cooling, lubrication -> engine coolant temperature regulation faye ° | |
information, navigation, communication, entertainment -> warning display symbols - | functionality ->
> low coolant\coolant temperature warning display activates
information, navigation, communication, entertainment -> instrument displays -> functionality ->
display of coolant temperature increasing
New workshop code
Object of complaint Complaint type [Position|
engine -> cooling system -> coolant pump -> coolant pump bearing housing | leaks -> not watertight [|
Vehicle data
EA825 4.0 Itr. V8 TFSI
Sales types
= feoaofa [ows iPS
zoxja_| iowa Fi)

iowa [ious PO
= facia [sommes
= feoja [ido OP
= feozsja [id
= feozsja [io
= feoosla [ions PO
= fosla [owns FO
|; zozgfa | fw
[aorta | owes
[_Jaozsfa | ovo’
Documents

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Technical Service Bulletin Transaction No.: 2074303/10
19 Engine: cooling system - red coolant temperature/coolant level warning lamp on - .
4.0 ltr. V8 TESI Release date: Aug 19, 2025
Condition
REVISION HISTORY
revision [pate [purpose
wo | | Revised header (updated model years)
| 06/27/2025 | Revised Service (Updated documentation instructions)
06/26/2025 | Revised Service (Updated inspection instructions)
Revised Warranty (Updated accounting instructions)
Customer states:
+ The red coolant warning lamp lights up:
— Switch off the engine and check the coolant level.
or
+ Coolant temperature: too high. Please let the engine run with the vehicle stationery.
Workshop findings:
+ Coolant loss at the front end of the engine.
and/or
+ The engine is overheating.
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

Not applicable.
Service
Step 1
Check whether there is a visible external leak in the area surrounding the mechanical coolant pump.

© NOTICE

Note: The mechanical coolant pump on the EA825 V8 TFSI engine is behind the coolant distributor.

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

Map Controlled Engine
Z Cooling Thermostat
SS F265
oS , 4 SS
| ~ he oo tant distribution
SS f a module
SF tee
. NL
< Re a7 ie
7 eS
ee
> >;
- P
bs y
Gasket ————_____&_
Coolant pump/vacuum
regulating assembly

Figure 1. Coolant distribution

~ Coolant distributor
ve > .
~ ~\) Vd 7
) \ | Leakage reservoir for mechanical
\ = coolant pump
=
¢ /
Sy
Figure 2. Coolant distributor and leakage reservoir
A fresh coolant leak in the area of 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.
If a fresh leak is detected, please note that it is not necessary to replace the coolant distributor. In this case,
replacing the mechanical coolant pump, per the workshop manual, is sufficient.
If no fresh coolant is visible from the mechanical coolant pump or the coolant distributor, it may be what is known
as a “cosmetic leak” from the mechanical coolant pump. Replacing the mechanical coolant pump is therefore not
intended for this reason.
In either case, proceed with step 2.
Step 2
Perform a functional check on the switch valve for the mechanical coolant pump N649 using ODIS.
Also, always check whether a coolant leak has occurred at the vacuum connection of the mechanical coolant pump
towards N649. If there is any coolant in the vacuum connection of N649 or in the vacuum hose between the
mechanical coolant pump and N649, replace N649, the mechanical coolant pump, and the vacuum hose between
N649 and the mechanical coolant pump (Figure 5, item 13).
Step 3
This step is only necessary if no issues are identified in step 1 and step 2, and the customer complained about a red
coolant TEMPERATURE warning.
First ensure no other TSB applies. If another TSB applies, please work through it first then reassess the customer
complaint.
If no other TSB applies, or the customer complaint (red coolant temperature warning appears) is still present,
remove the coolant distributor and check the switching function of the mechanical coolant pump.
To do so, connect a vacuum pump to the vacuum connection of the mechanical coolant pump.
Please note:

+ If there is no vacuum applied to the vacuum connection of the mechanical coolant pump, the modulating
piston (orifice panel) must be fully retracted into the pump housing.
zz - =| =
~ 7 s
= a SS bin ~
y a iT
es . a i F = ee
=. —- Sie aie emer
——_ or "| wry
= i <a) ee
— a
nae SSN 5 eae
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.

= pa ee
a =
a, ts \ rs = oo » Pi : 2
“oe a a
Be ee ee. ny
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.

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as |
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oe! 4
Se
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12 CEE a we s
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11 YR SOS a
10 » ENG
a FASS
SOY - . n
y peck iS +
. Pin F< Ae
8 ~< pe" yo
_ <p Se, ANY
ss ( =~
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o-Ps , bs
5) 2
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adh
1
21 20 19 18
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: + Ifthe 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 20 TU
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 2074303/10
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.
©2025 Audi of America, Inc. All rights reserved. The information contained in this document is based on the latest
information available at the time of printing and is subject to the copyright and other intellectual property rights of
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