The contact owns a 2012 Mercedes-Benz ML350. The contact stated while driving uphill at an undisclosed speed, the accelerator pedal was depressed; however, the vehicle failed to accelerate as intended. In addition, the contact stated that the vehicle was shaking abnormally. The contact stated that the abnormal shaking occurred at various speeds. The vehicle was taken to the dealer where it was…
2012 Mercedes-Benz ML-Class engine problems
severe 15 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
15
Recalls
0
Avg fix
$3,100
1crash
When does it fail?
Of the 15 engine complaints filed for the 2012 Mercedes-Benz ML-Class, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Of the 4 model years of Mercedes-Benz ML-Class we track for engine problems, this one carries the most owner complaints on file — 15.
Engine accounts for 23% of all owner complaints filed against this vehicle, across 8 categories tracked.
The failure pattern owners describe
The 2012 ML-Class engine complaints cluster around several distinct failures. Most prevalent is random stalling—the engine dies at traffic lights or during freeway driving without throwing diagnostic codes, making it impossible for dealers to pinpoint the cause. One owner reported this happens as a brand-new car; another had the problem occur 5-6 times in the first year. A dealer informed one owner that Mercedes headquarters is aware of the stalling symptoms but has no fix.
Fuel system issues include a loose fuel line at 86,432 miles that spilled diesel fuel on the roadway, traced to failed clamps. Another owner reports strong diesel fuel odor and oil leak requiring three dealer visits in less than four months without resolution.
Mechanical failure modes include timing chain failure around 65,000 miles causing abnormal shaking and loss of acceleration; a defective piston set at just 200 miles; and camshaft failure around 96,000 miles (with a Technical Service Bulletin acknowledging the problem). Crankshaft position sensor failure prevented restart at 145,000 miles. One shop mechanic referenced "stroker engines" causing loud startup noise in over 80 vehicles.
The DEF (Blue Additive) emissions system illuminates the check engine light at 42,500 miles; Mercedes charges $3,000 to repair and won't cover it, with owners reporting the company is aware of the defect but won't warranty it.
Failure modes owners describe
Power loss / stalling at stop or during driving
Vehicle loses power or stalls spontaneously, often at traffic lights or stops, but also while in motion. No consistent diagnostic codes appear; dealers cannot reproduce the issue. Multiple owners reported this as a new-car problem. One dealer mentioned Mercedes headquarters is aware of the symptoms but has no fix.
When: As early as first week of ownership; occurs randomly; one case at 8,000 miles, another at 21,000 miles
Symptoms owners cite: Engine stalls at traffic lights or stops; Spontaneous power loss while driving; Engine shuts down without warning message; Vehicle must be shut down 30-45 minutes to reset before continuing; No check engine light or diagnostic codes logged; Stalling on consecutive days in some cases
Repairs/costs cited: One dealer replaced high-pressure fuel pump; problem persisted. Most cases unrepaired due to dealer inability to diagnose.
Recalls/TSBs owners mention: Mercedes headquarters aware of symptoms but no fix available. MBUSA contacted but showed no urgency.
Loud engine noise on startup (possible stroker engine defect)
Engine produces very loud noise when started, sounds like it may shut down. One shop reported over 80 vehicles with identical problem. Mechanic indicated stroker engines are the cause and engine replacement needed.
When: Present from initial startup; no warning light when first appeared
Symptoms owners cite: Very loud noise on engine startup; Feels like engine is about to shut off; Potential risk of catastrophic failure
Repairs/costs cited: Engine replacement required per workshop assessment
Timing chain failure
Timing chain fails at relatively low mileage. Vehicle shakes abnormally and fails to accelerate properly when problem occurs.
When: At approximately 65,000 miles
Symptoms owners cite: Abnormal shaking at various speeds; Failure to accelerate when pedal depressed; Engine shaking uphill
Repairs/costs cited: Timing chain replacement required
Recalls/TSBs owners mention: Manufacturer aware but provided no assistance
Crankshaft position sensor failure
Check engine light illuminates while driving; vehicle will not restart. Diagnostic code for crankshaft position sensor detected. Failure at 145,000 miles.
When: At approximately 145,000 miles
Symptoms owners cite: Check engine warning light illuminated while driving at 40 mph; Vehicle will not restart; Failure persisted after clearing sensor code
Codes mentioned: crankshaft position sensor
Repairs/costs cited: Not repaired due to cost
Fuel line clamps failure / fuel leak
Fuel line clamps failed, causing fuel line to come loose while driving at highway speed. Diesel fuel spilled on vehicle and roadway. Two fuel line clamps required replacement.
When: At 86,432 miles
Symptoms owners cite: Fuel line came loose while driving 65 mph on highway with cruise control; Engine lost all power; Diesel fuel spilled on vehicle and roadway
Repairs/costs cited: Two fuel line clamps replaced. Total repair cost $321.88 (not including tow).
Recalls/TSBs owners mention: Mercedes provided no assistance with repair reimbursement. Roadside assistance paid for tow.
Camshaft failure
Check engine light illuminates after starting vehicle. Dealer diagnosed camshaft failure. Technical Service Bulletin exists for this issue. Vehicle warranty had expired at time of failure.
When: At approximately 96,000 miles
Symptoms owners cite: Check engine warning light illuminated after starting
Codes mentioned: camshaft
Repairs/costs cited: Not repaired; warranty expired
Recalls/TSBs owners mention: Dealer cited expired warranty; Technical Service Bulletin exists for camshaft failure
DEF (Blue Additive) emission system failure
Check engine light illuminates related to Blue Additive emissions system. Owners report this is a common issue that Mercedes will not cover under warranty. Repair cost $3,000.
When: At 42,500 miles
Symptoms owners cite: Check engine warning light
Codes mentioned: emission / blue additive
Repairs/costs cited: $3,000 repair cost
Recalls/TSBs owners mention: Mercedes will not cover under warranty; owners report Mercedes is aware of the issue but does not stand behind the product
Diesel fuel smell and oil leak
Strong diesel fuel smell and oil leak in ML350 BlueTEC engine. Smell strong enough to cause severe headaches and nausea. Owners visited authorized dealer 3 times in less than 4 months with same complaint.
When: Chronic issue over multiple visits
Symptoms owners cite: Strong diesel fuel smell in cabin; Oil leak; Smell of burning plastic; Severe headache from fumes; Nauseous feeling; Requires stopping car and exiting for fresh air; Worse while driving, pronounced on highways
Repairs/costs cited: Unresolved after 3 dealer visits in less than 4 months
Engine startup difficulty and piston defect
Vehicle does not start until after several attempts. While driving, loses power. Dealer diagnosed piston defect requiring replacement. Failure occurred very early in vehicle ownership at 200 miles.
When: At 200 miles (virtually new)
Symptoms owners cite: Difficulty starting; multiple attempts required; Power loss while driving
Repairs/costs cited: Pistons replaced
Recalls/TSBs owners mention: Manufacturer contacted
Oil leak
Oil leak reported on 2012 ML350. Manufacturer notified but vehicle out of warranty. Owner offered 15% discount on repair.
When: Out-of-warranty condition
Symptoms owners cite: Oil leak
Repairs/costs cited: Out of warranty; 15% repair discount offered
Recalls/TSBs owners mention: Manufacturer cited out-of-warranty status
Synthesized from 15 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 4 most recent
This happened as a new car, only now, after it happened about 5 or 6 times, we came to know this weired and dangerous problem-it loses the power at a stop; at red light, and even when we tried to start to move. When it happened, at first several times, we were thinking maybe I did something, after 5 to 6 times happened to me and to my wife, we just came to understand it is such dangerous problem.…
Vehicle loses power after a few hours of driving. This problem does not show any error message on the dashboard, and the dealer cannot fix this problem after multiple attempts. Last trip to the dealer which was 2 weeks ago, they insisted that nothing was wrong. Here are examples of how serious the problem is, I was stranded and had to shut the car down for 30 - 45 minutes to let the car reset…
Cuando enciendo mi guagua hace un ruido muy fuerte y se siente como si se va a apagar. El motor se puede romper en cualquier momento. Si se ha llevado a diferentes talleres para confirmar el ruido y me refieren que son mas de 80 guaguas que han visitado su taller con el mismo problema. No presenta ninguna advertencia cuando aparecio por primera vez. En el taller me dicen que se debe cambiar el…
Had engine trouble with your 2012 Mercedes-Benz ML-Class?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2012 Mercedes-Benz ML-Class?
It's a meaningful issue. 15 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $3,100.
At what mileage does the engine typically fail?
Across the 9 complaints that reported odometer mileage, most engine failures cluster between 21,200 and 86,432 miles, with the median around 49,000. A quarter of owners report trouble before 21,200; a quarter make it past 86,432. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2012/Mercedes-Benz/ML-Class.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.