Teardown shows how a simple oil leak harmed the M276 V6

M276 DE 35 V6 widely used from 2010 to 2017

The Mercedes M276 DE 35 is a 3.5-liter naturally aspirated V6 engine used from 2010 to 2017 in multiple models, including ML 350, C 350, E 350, S 350, GLE 350, and GLK 350. Only the A-Class and B-Class front-wheel drive cars did not use it.

The engine had minor faults such as oil leaks and camshaft adjuster or cam follower issues. A core exchange M276 engine teardown by the “I Do Cars” YouTube channel examined a failed unit with no VIN or mileage history. The cause of failure was identified step-by-step.

Initial inspection showed a damaged oil pan

Before teardown, a hole in the oil pan and a crankshaft that would not rotate were noted. No evidence showed a connecting rod had exited the block. The oil pan came from another broken engine.

The electrical harness appeared intact, indicating careful removal from a 2014 or 2015 ML 350. The direct injection motor showed carbon buildup and minor oil seepage in the head. The valvetrain seemed fine until the valve cover was removed.

Valve cover removal revealed worn components

Removing the valve cover revealed one worn cam follower and camshaft scoring. The cam lobes showed wear, but not enough to harm journal bearings. There was no complete timing failure.

The head and timing cover were removed because these findings did not match a catastrophic failure. The water pump, oil pump, and tensioners were removed before loosening end caps. The crankshaft then turned, allowing bearing inspection.

Unattended oil leak led to belt failure

The block showed minor cylinder wall scoring, and the oil filter had no shrapnel. The failure was traced to an unaddressed minor oil leak spilling onto the serpentine belt.

The leaking oil degraded the serpentine belt; belt debris was drawn toward the crank, dislodging the oil-pump chain and ultimately causing the pump to seize

Pump seizure ended the engine’s operation

Pieces trapped in the crank area overextended an oil pump tensioner, seizing the pump. The engine stopped immediately, with the crank making its last powered rotation as the vehicle coasted to the roadside.

According to Autoblog, little metal debris was visible in the filter; the teardown suggests the oil-pump seizure halted circulation quickly, limiting the spread of wear particles. Owners are advised to repair leaks quickly, perform careful oil services, and replace tensioners before their lifespan ends to avoid such failures.

Mercedes to halt EQE and EQS US production

According to Electrive, on July 22, 2025, Mercedes-Benz confirmed it will temporarily stop US production of EQE and EQS models, including SUVs. Orders for new configurations will not be accepted. The Tuscaloosa plant will cease building them on September 1, 2025.

Only the EQB compact SUV will remain in production there after that date. Vehicles already scheduled for production will be completed, and buyers are encouraged to choose discounted inventory units.

Price cuts announced for remaining EV models

Mercedes announced new U.S. MSRPs for MY2026, EQS SUV at $91,100, EQE Sedan/SUV at $66,100, and EQS Sedan at $101,400 (ex-dest.). The adjustments follow a soft EV market; third-party analyses cite pricing, styling reception, and incentive changes as factors.

The EQS Sedan is reduced from $105,500 to $101,400. Many dealers still have 2025 models in stock. The company attributes low demand to bland design and the end of EV subsidies in the United States.

EQ strategy changes after poor model reception

Mercedes-Benz sales for EQE and EQS models drop by 50 percent in the first half of 2025 compared to 2024. The company’s EV design, different from gasoline models, did not appeal to conservative US buyers.

The EQ branding is being phased out. EVs, such as the CLA EV, will be integrated into standard model lines. The CLA EV, due later in 2025, has been reviewed positively and is seen as a rival to the Tesla Model 3.

CEO response to April 2019 Xi’an oil leak case

As per Yicai Global, on April 17, 2019, Nicholas Speeks, CEO of Beijing Mercedes-Benz Sales Service, apologized for an oil-leak case in Xi’an, China. A buyer had purchased a CNY 660,000 car that leaked oil before leaving the dealership.

The dealership, Xi’an Lizhixing Automobile Service, offered only an engine replacement, not a refund. The buyer also discovered a CNY 15,000 financial service fee. Speeks said he would demand more than an engine change if he were the customer.

Legal limits on Mercedes-Benz dealer control

Speeks stated that Chinese market monopoly laws prevent automakers from interfering directly between dealers and customers. Mercedes-Benz has about 600 dealers in China, which are hard to control directly.

Xi’an market regulators began investigating the case, working with a forensic team from Beijing Mercedes-Benz Sales Service. The China Banking and Insurance Regulatory Commission also investigated the financial fee practice.

Mercedes-Benz denies collecting extra fee

Mercedes-Benz Financial Services said it does not collect financial service fees from dealers or customers. The company pledged to ensure its dealers comply with rules and act honestly.

Speeks described the Xi’an case as isolated among Mercedes-Benz’s 3.6 to 3.7 million Chinese customers. He called for all dealers and manufacturers in China to learn from it.

December 18 2014 recall for oil leak risk

According to Reuters, on December 18, 2014, Mercedes-Benz recalled 4,871 US sedans and SUVs for possible oil leaks from the chain tensioner gasket in four-cylinder diesel engines. The leak risked engine stalling or fire.

Dealers were to replace the gasket at no cost. Affected models included 2014–2015 E250 BlueTec and E250 BlueTec 4Matic, 2015 ML250 BlueTec 4Matic, and GLK250 BlueTec 4Matic SUVs.

Oil leaks posed additional road hazard risk

Documents filed with the National Highway Traffic Safety Administration said leaking oil could also create a road hazard for other vehicles, raising crash risks.

A Mercedes spokesman said the company knew of no US incidents caused by the defect. Letters to affected customers were scheduled to be mailed beginning December 19, 2014.

April 15 2019 viral Xi’an oil leak video

A video posted April 12, 2019, by People’s Daily showed a customer in Xi’an sitting on a showroom car, protesting an oil leak in her new Mercedes-Benz. She also complained of a CNY 15,000 fee.

The Xi’an market regulation bureau began investigating Xi’an Lizhixing Automobile Co. Ltd., ordering that the buyer be refunded. Mercedes-Benz issued a statement denying that it charges such fees.

Customer disputes dealership’s resolution claim

Sina Shaanxi reported that the dealership claimed to have reached an agreement with the customer, but she denied receiving an official reply. On April 13, 2019, Mercedes-Benz apologized for her “unpleasant experience” and sent a team to Xi’an.

The buyer released an 18-minute meeting audio, accusing staff of making excuses. Social media users shared similar complaints, and other Chinese dealerships faced public criticism.

Mercedes-Benz EQS uses augmented reality to enhance navigation and guide drivers with precision. See the full story in how Mercedes-Benz EQS AR guides every turn.

July 24 2025 solid-state EV battery testing

On July 24, 2025, Mercedes-Benz said it was testing lithium-metal solid-state battery EVs with over 600 miles of range. Prototypes, including a modified EQS, have been tested in the UK since February.

The battery, made with Factorial Energy and AMG High-Performance Powertrains, offers 25 percent more range and uses a sulfide-based solid electrolyte. Production is targeted before 2030. Mercedes expects this to cut costs and improve safety compared to current lithium-ion batteries.

The top 10 electric convertibles for 2025 include current and upcoming models ready to hit the road. Get the complete list in The 10 best electric convertibles available now and coming soon.

Ever seen a tiny oil leak take down a powerhouse like the M276 V6? Share your thoughts below.

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This slideshow was made with AI assistance and human editing.