initial observation started happening intermittently a week before the car become inoperable. When the vehicle came to a stop like at a light the engine would sound like it was going to almost turn off like a rattle noise and a popping sound or like I hit a plastic bag sound on acceleration. Then the day it broke down I was merging onto interstate 15 I heard the same popping sound, the engine…
2018 Mercedes-Benz C-Class engine problems
moderate Owners of the 2018 Mercedes-Benz C-Class have filed 34 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
34
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2014 C-Class | 12 |
| 2015 C-Class | 97 |
| 2016 C-Class | 76 |
| 2017 C-Class | 60 |
| 2018 C-Class (this page) | 34 |
| 2019 C-Class | 10 |
| 2020 C-Class | 4 |
| 2021 C-Class | 5 |
What stands out
Owners have filed 34 engine complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Engine accounts for 27% of all owner complaints filed against this vehicle, across 9 categories tracked.
The failure pattern owners describe
The 2018 C300 shows a pattern of engine problems consumers link to defects, not abuse. The most common complaint is positive crankcase ventilation (PCV) regulator valve failure, reported on nearly two dozen vehicles, typically between 28,000 and 67,000 miles. Check engine code P052E lights up; repair costs $1,200–$2,500 and requires 6 hours of labor. Owners note the defect is widespread, documented on Mercedes forums and Reddit, and Mercedes has issued an improved part design on newer models—yet refuses to recall older vehicles or cover repairs even on extended warranties.
A smaller subset reports catastrophic piston cracks requiring complete engine replacement ($16,500 in one case) at 68,000–90,000 miles on otherwise well-maintained, oil-changed vehicles. Owners also report engine stalling at stops or traffic lights, white smoke from the exhaust, and crankshaft faults. The safety angle appears genuine: two narratives cite near-accidents when the engine quit on an interstate, creating hazardous situations.
Dealers are aware of the PCV problem—multiple owners state this explicitly—yet treat each failure as an individual warranty claim. Owners consistently say Mercedes should recall this rather than force consumers to absorb the cost after 28,000 miles.
Same Mercedes-Benz C-Class engine reports on nearby years: 2015 · 2016 · 2017
Failure modes owners describe
Cracked pistons
Pistons crack, causing engine failure and the need for complete engine replacement. Occurs at relatively low mileage on well-maintained vehicles.
When: 69,000 miles, 68,000 miles, 90,000 miles
Symptoms owners cite: Engine rattle and popping sound on acceleration; Engine stalling or running rough at stops; Violent shaking; Check engine light illumination; Complete loss of power mid-drive
Repairs/costs cited: Engine replaced ($16,500 in one case); dealerships unable to articulate cause for otherwise well-maintained vehicles
Positive Crankcase Ventilation (PCV) regulator valve failure
PCV regulator valve fails prematurely, triggering check engine light with code P052E. Owners report this is a widespread, known defect on 2018 C300 models. Mercedes has issued updated part design on newer vehicles but provides no recall or warranty coverage.
When: 28,000 to 67,000 miles; commonly occurs shortly after warranty expiration
Symptoms owners cite: Check engine light illumination; Engine stalling or hesitation to restart at stops; Oil and gas leaks from PCV valve; Increased oil consumption; Emission test failure; Rough idle
Codes mentioned: P052E, P052W-71, P060A-00
Repairs/costs cited: Repair costs $1,200–$2,500; requires 6 hours labor at dealer; owners report the issue can recur approximately every 35,000 miles after repair
Recalls/TSBs owners mention: Mercedes-Benz has designed an improved replacement part and issued it on new vehicles, indicating awareness of the defect, but has not issued a recall; not covered under standard or extended warranties
White smoke from exhaust with engine shutdown
White smoke emits from the exhaust while driving at normal speeds, accompanied by check engine light. After vehicle shutdown, smoke clears.
When: 54,000 miles
Symptoms owners cite: White smoke from exhaust; Check engine light illumination
Repairs/costs cited: Vehicle towed to dealer but was not diagnosed or repaired
Engine stalling at stops
Engine stalls or fails to restart when the vehicle is at a complete stop (traffic lights, parking lots). Intermittent occurrence.
When: Reported at approximately 27,000 miles and beyond
Symptoms owners cite: Engine stalling at traffic lights; Engine stalling in parking lots; Engine fails to restart immediately; driver must manually restart; Occurs intermittently (up to 4 times in 5 months reported)
Crankshaft defect
Diagnostic testing reveals crankshaft fault, requiring expensive repair on a vehicle with regular maintenance.
When: Mileage not specified; one case at initial diagnosis
Symptoms owners cite: Check engine light
Repairs/costs cited: Repair cost approximately $1,800
Synthesized from 34 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 7 most recent
When at a stop the engine will not restart sometimes. I have to start the engine manually. This has happened to me four times in 5 months .
My vehicle only had 31,000 miles and I experienced engine failure. I bought a new engine for 16, 500. 00 dollars. Mercedes Benz did nothing. I almost got in to several accidents because the engine completely stop on the interstate. Almost got hit by several cars. This is unacceptable.
My car was diagnosed with positive crankcase ventilation regulator valve performance failure. This should be recalled by the manufacturer because many c300 are having this very same issue.
Check engine light appeared.I took it to Mercedes and they said the crankshaft was faulty. I had to repair it and it cost me about $1800.00.
Engine code: P052e - the widest spread engine issue on Mercedes which fails emissions testing. Crankcase ventilator issue which leads to stalling.
Positive crank case valve failure. Check engine light on. Mechanic started this was extremely common and a costly repair on lower mileage Mercedes Benz vehicles. Mercedes Benz forums also mention this is extremely common and frustrating. This happened at slightly over 50k miles on my vehicle. Error code P052e
Had engine trouble with your 2018 Mercedes-Benz C-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 2018 Mercedes-Benz C-Class?
It's a documented issue but not catastrophic. 34 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Based on the 34 complaints filed, engine issues most often appear around 54,000 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/2018/Mercedes-Benz/C-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.