The contact owns a 2012 Mercedes-Benz E350. The contact stated that after retrieving the vehicle from the dealer, the check engine warning light was illuminated. The vehicle was taken back to the dealer where it was diagnosed that there was oil contamination through the camshaft sensor. The contact was informed that the engine wiring harness needed to be replaced. The vehicle was not repaired.…
2012 Mercedes-Benz E-Class engine problems
severe Owners of the 2012 Mercedes-Benz E-Class have filed 11 NHTSA complaints about the engine at roughly $3,100 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See engine across all vehicles →
Complaints
11
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2008 E-Class | 15 |
| 2009 E-Class | 5 |
| 2010 E-Class | 8 |
| 2011 E-Class | 9 |
| 2012 E-Class (this page) | 11 |
| 2013 E-Class | 11 |
| 2014 E-Class | 11 |
| 2015 E-Class | 4 |
| 2016 E-Class | 5 |
1fire
When does it fail?
Of the 11 engine complaints filed for the 2012 Mercedes-Benz E-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
No new NHTSA engine complaint has been filed on this vehicle in over 4 years — the issue may be aging out of the active population.
The failure pattern owners describe
The 2012 E-Class engine failures cluster around the timing and valve-train system. Cold-start rattling and grinding are the most common complaint, traced to failing secondary chain tensioners and cam adjusters. Multiple owners brought cars in three or more times for the same noise; dealers replaced tensioners ($1,500–$1,900) without fixing it, then suggested cam work ($5,000+) without a firm diagnosis. One owner's $1,497 repair estimate ballooned to $12,000 after the engine cracked during subsequent work; the dealer would not document what happened.
Camshaft sensor failures show up at 54,000–87,000 miles with check engine lights and oil leaking into the wiring harness. One dealer finally confirmed the cam sensor triggered a cascade that damaged O2 sensors and the entire harness. The manufacturer offered partial financial assistance on some repairs but no recall.
A dramatic intake manifold explosion occurred during a cold soak—the hood bent upward with force—without any obvious trigger. The dealer could not identify a cause.
Other owners reported ticking under load, hard starts, and random stalling at traffic lights with no warning lights. Service advisors in multiple states told owners they've seen several E350s with identical camshaft wear.
Same Mercedes-Benz E-Class engine reports on nearby years: 2013 · 2014
Failure modes owners describe
Chain tensioner and cam adjuster noise
Secondary chain tensioners rattle until oil pressure builds on cold start. Later complaints reveal cam adjuster failure causing rattling/grinding metal-on-metal noise that persists even after tensioner replacement.
When: Cold start; can persist on warm start
Symptoms owners cite: Rattling noise from engine on cold start; Grinding metal-on-metal noise on cold and warm start; Noise fades as oil pressure builds
Codes mentioned: P001685 — intake camshaft position implausible relative to crankshaft bank 1
Repairs/costs cited: Tensioner replacement: $1,497–$1,900. Cam adjuster work and secondary repairs: $5,000–$12,000.
Recalls/TSBs owners mention: Dealers offered tensioner replacement; Mercedes initially suggested camshaft work but diagnosis took months without resolution.
Engine crack and timing chain failure
Engine block cracked after cam adjuster and timing-related repairs, discovered during follow-up diagnostics. Owners suspect manufacturing defect or service mishandling caused internal damage.
When: Discovered after attempted repair of cam/tensioner issues
Symptoms owners cite: Check engine light; Engine does not operate properly after repair
Repairs/costs cited: Extensive engine repair and rebuild: $12,000+. Repairs incomplete; engine required re-disassembly.
Recalls/TSBs owners mention: Service noted 'no consequential damage expected' but engine later cracked; no technical documentation provided to owner.
Intake manifold explosion
Intake manifold exploded with enough force to bend hood upward 2 inches during initial door pull after cold soak. No obvious cause identified by dealer; potential safety hazard.
When: Cold morning, 12 hours since last start
Symptoms owners cite: Sudden explosive rupture of intake manifold
Repairs/costs cited: Parts replacement only: $8,000. Root cause unidentified.
Recalls/TSBs owners mention: Dealer unable to identify cause; company denies knowledge of design flaw despite owner assertion of similar failures.
Camshaft sensor failure and wiring harness contamination
Camshaft sensor fault triggers check engine light and spreads contamination through engine wiring harness and O2 sensors. Oil contamination reported in wiring, suggesting seal or internal breach.
When: 54,700–87,000 miles
Symptoms owners cite: Check engine light illumination; Oil contamination in wiring harness; Sensor electrical failure spreading to adjacent systems
Codes mentioned: Defective camshaft sensor, O2 sensor failure
Repairs/costs cited: Engine wiring harness replacement required; repairs pending in some cases.
Recalls/TSBs owners mention: Manufacturer notified and offered partial financial assistance on repairs but no recall or extended coverage noted.
Random stalling at traffic lights
Engine shuts off without warning at stop lights, forcing restart at green light. Represents safety hazard with traffic behind vehicle.
When: While stopped at traffic light
Symptoms owners cite: Engine shuts off randomly without warning lights; Requires manual restart
Engine ticking/tapping under acceleration
Ticking or tapping noise from engine bay during acceleration, especially uphill. Suggests internal mechanical wear or bearing issue.
When: Under acceleration, worst uphill
Symptoms owners cite: Ticking/tapping noise from engine
Hard starting
Engine difficult to start, owner suspects timing chain deterioration may be root cause.
Symptoms owners cite: Difficult to start
Synthesized from 11 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 2 most recent
Ticking/ tapping noise from the engine bay when car is excelerating, especially when going uphill. *tr
Had engine trouble with your 2012 Mercedes-Benz E-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 E-Class?
It's a meaningful issue. 11 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?
Based on the 11 complaints filed, engine issues most often appear around 72,782 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
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/E-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.