Mercedes-Benz bulletin LI20.10-P-078510
What it saysComplaint Red cooling system malfunction warning due to overheat. NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Feb 6, 2025, received Feb 12, 2025, about the engine. It names 6 model years (2022–2025). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
Get the next Mercedes-Benz bulletin for your model by email Weekly, only when something new is filed. Nothing else; one-click unsubscribe.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationComplaint Red cooling system malfunction warning due to overheat. Low engine performance. Check engine light on. Fault codes may be stored: P21814B The cooling system has a malfunction. There is a fault due to overtemperature. P2B8500 The rpm of the coolant pump is too low. Cause Various Remedy Check for loose plug at electrical connectors of high temp coolant pump (M43/10 or M75/11) by gently pulling on connector housings. Create a TIPS case and submit to powertrain team inbox if a loose plug is found at the coolant pump. Include: -Initial quick test -Details on any damage found to engine or cooling system. Include photos if applicable. -Any other relevant details.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI20.10-P-078510 | Service bulletin | Feb 6, 2025 | 11014223 | PDF, 35 KB |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themA vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
Email me new Mercedes-Benz bulletins for one of these models
A weekly email, sent only in a week when Mercedes-Benz files something new with NHTSA for the model you pick — service bulletins, campaigns, warranty extensions, over-the-air notices, every model year. Nothing else is sent; one-click unsubscribe in every message. Separate from recall alerts.
What owners reported
Source: NHTSA complaint databaseOwners of the 6 model years this bulletin names have filed 189 complaints with NHTSA since 2015. 21 of them name Engine — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
Radiator started leaking in <3000 miles of driving the brand new GLE 580 Mercedes Benz. Twice I got errors in the car that stated check coolant level I could hear liquid moving in the front of the car when I parked it. Once while driving, the AC totally stopped working and on the entire drive, I couldn't feel the cool air.
2025 Mercedes-Benz GLE-Class · Engine · filed with NHTSA Jan 25, 2026 · ODI 11713270
Driving a 2024 mercedes c300 on the florida turnpike in the left lane at 70 MPH the engine suddenly slowed down. While the vehicle slowed in heavy traffic I was able to merge to the outside lane where it stopped. I called mercedes emergency who suggested waiting a while and try starting the vehicle .
2024 Mercedes-Benz C-Class · Engine · filed with NHTSA Jul 19, 2026 · ODI 11751377
Car fails to accelerate past 25 mph when entering roadway. Roadway area is 45mph and vehicle would not accelerate to reach safe levels. This out myself and occupants of my vehicle in danger as traffic is already at the 45+ mph limit. Vehicle has 30,000 miles. Engine light came on after incident
2022 Mercedes-Benz C-Class · Engine · filed with NHTSA Jun 18, 2026 · ODI 11745068
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the engine
Source: same model, same component group55 other manufacturer communications filed against these Mercedes-Benz models under the same component group (engine), newest first. The eight newest are listed; the rest are on the Mercedes-Benz list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| LI18.00-P-073137 | Service bulletin | Sep 26, 2026 | Complaint Sporadic warning message in instrument cluster "Engine oil pressure stop switch off vehicle" (or similar) is shown in red on vehi… |
| LI20.10-P-075374 | Service bulletin | Sep 17, 2026 | Complaint Red coolant warning in instrument cluster. Fault codes U019F00 or U019F87 current/stored in MRG1 control unit. Cause Various cause… |
| PSL-NCU Return Parts 8/14 | Other | Aug 15, 2026 | Dear Mercedes-Benz USA Dealers, The part numbers listed in the chart below should no longer be installed, and any existing stock must be ret… |
| LI01.20-P-080884 | Service bulletin | Aug 12, 2026 | Complaint Oil leaks found on M176 or M177 engines diagnosed to be from the cylinder head cover area Cause Unknown (under investigation) Reme… |
| LI07.10-P-080384 | Service bulletin | Aug 7, 2026 | Complaint Customer reports Check Engine Light with possible loss of power concern. The Following DTC's are present • P210185 - The throttle… |
| LI20.10-P-072886 | Service bulletin | Jul 24, 2026 | Complaint Check Engine Light ON with DTC P012800 "The Coolant Temperature is Below the Specified Temperature" active and/or stored in the ME… |
| Emissions - 2024100016 | Emissions | Jul 24, 2026 | Mercedes-Benz AG (“MBAG”), the manufacturer of Mercedes-Benz, has determined that on certain MY 2019-2021 C-Class, G-Class, GLC, GT, S-Class… |
| LI01.30-P-072328 | Service bulletin | Mar 27, 2026 | Complaint -Check engine light illuminated. -Engine runs rough. -Poor shifting or jerking when accelerating. -Fault codes stored related to m… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Mercedes-Benz, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Mercedes-Benz LI20.10-P-078510 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the LI20.10-P-078510 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way. Every Mercedes-Benz warranty extension on file lists the ones Mercedes-Benz has filed.
Which vehicles does LI20.10-P-078510 cover?
The manufacturer filed it against 6 model years: 2024 Mercedes-Benz C-Class, 2023 Mercedes-Benz C-Class, 2022 Mercedes-Benz C-Class, 2025 Mercedes-Benz GLE-Class, 2024 Mercedes-Benz GLE-Class, 2023 Mercedes-Benz GLE-Class. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.