Coolant leak at expansion reservoir level sensor connection
Topic number

LI20.30-P-078666

Version

2

Function group

20.30 - Coolant expansion/overflow tank

Date

7/29/25

Validity

Model year 2025 GLE and GLS-class vehicles
Production date 09/2024 and later

Reason for change

Additional symptom of coolant wicking through contacts

Complaint
Coolant level warning in instrument cluster.
Coolant odor or leaking from coolant expansion reservoir.

Cause
Coolant wicking through electrical contacts, or level sensor electrical connections not present in expansion reservoir.

Remedy
1.
2.
3.
4.

Inspect expansion tank level sensor electrical connection for wicking coolant or missing contacts. Additionally
the triangular sticker may not be present on top of reservoir. See example of OK and NOK part.
Replace expansion reservoir if level sensor contacts are confirmed to be missing or wicking coolant.
Repair any damage to wiring or electrical contacts on wiring harness.
Create a TIPS case with supporting photos and submit to the IFQ inbox for information. Vehicle can be released
after repair is complete.

Attachments
File

Description

NOK part.jfif

NOK parts with pins and sticker missing

OK part.jfif

OK part with pins and sticker present

WIS-References
Document number

Title

Note

AR20.30-P-4949MRX

Remove/install coolant expansion re- Engine M254
servoir

AR20.30-P-4949MSC

Remove/install coolant expansion re- Engine M256
servoir

AR20.30-P-4949MNO

Remove/install coolant expansion re- Engines M176 and M177
servoir

Disclaimer
30.07.2025 16:22
© Copyright Mercedes-Benz AG

CCUSHWA

Page 1 / 2

NOTE: The information contained in this document is intended for use by trained, professional technicians with the
knowledge to properly and safely perform diagnosis and repairs on Mercedes-Benz vehicles, using Mercedes-Benz
approved tools and equipment. It informs service technicians about conditions that could occur in certain vehicles and
provides information that could assist in proper vehicle diagnosis, service, or repair. It does not indicate that a defect
is present in any vehicle referenced in this document nor does it imply warranty coverage. DO NOT assume that a
symptom or condition, or a described cause of a symptom or condition, affects any particular vehicle or groups of vehicles, or that a described repair applies to any particular vehicle or groups of vehicles. There can be multiple causes
resulting in the same or similar symptoms or conditions described in this document, and trained professional service
technicians must use their diagnostic skills to make evaluations on a case-by-case basis. The information contained
in this document does not guarantee warranty coverage nor does it extend the vehicle’s warranty in any way.

Symptoms
Power generation > Engine cooling system > Function > Coolant level too low
Power generation > Engine cooling system > Display message > Coolant - Serviced Required
Power generation > Engine cooling system > Leakage > Has coolant loss

Parts
Part number

ES1 ES2 Designation

A1675009900

Quantity Note

Coolant expansion reservoir

EPC

1

X

Control unit/fault code
Control unit

Fault text

N10/6 - Front signal acquisition and actuation module
(Driver-side SAM) (BC_F213)

P25567B - The sensor 'Coolant level' has an electrical
fault. The fluid level is too low.

Operation numbers/damage codes
Op. no.

Operation text

30.07.2025 16:22
© Copyright Mercedes-Benz AG

Time

CCUSHWA

Damage
code

Note

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