Mercedes-Benz C-Class common problems and MOT failures
What goes wrong on a used Mercedes-Benz C-Class, year by year: known faults from UK buying guides, the parts flagged at MOT more than on other cars (from 358,846 MOTs done during 2025), and what to check before you buy one.
Pick the year
Most years have their own guide. The year is when the car was first registered (it’s on the logbook, or check the reg below).
2026202520242023202220212020201920182017201620152014201320122011201020092008200720062005200420032002200120001999199819971996199519941993
Generation guides: Mercedes-Benz C-Class W204 (2008–2014) · Mercedes-Benz C-Class W205 (2014–2021)
What usually goes wrong with a Mercedes-Benz C-Class?
Known faults reported by owners, mechanics and UK buying guides, in our own words. Most apply to certain years or engines only, so check which the car has.
- Cars registered 2022–2023 · All engines
Fuel pump recall
Some 2022-23 cars were recalled because the fuel pump impeller can deform.
At the viewing: Run the free DVSA recall check on the reg.
- Cars registered 2014–2021 · Diesel
Diesel emissions system faults
Particulate filter, NOx sensor and AdBlue problems are the main worry on diesels, especially ones used for short trips.
At the viewing: Watch for emissions or AdBlue warnings on the dash, and ask what journeys it’s done.
- Cars registered 2014–2021 · Cars with air suspension
Air suspension
Cars with air suspension can develop expensive faults that need a specialist.
At the viewing: Check the car sits level all round, look for uneven front tyre wear, and watch for suspension warnings.
- Cars registered 2014–2021 · Petrol
Petrol smell or leaks (petrol)
Petrol models can leak fuel from the pump area or crack plastic air pipes.
At the viewing: Smell around the car after a cold start, and listen for rough idle.
- Cars registered 2007–2013 · Diesel
Injector seals (diesel)
Injector seals and other engine seals can leak on the diesels.
At the viewing: Look for fuel or oil around the top of the engine.
- Cars registered 2007–2013 · Manual diesel
Dual-mass flywheel (manual diesel)
Manual diesels can wear out their dual-mass flywheel. Above 60,000 miles, check whether it's been done.
At the viewing: Listen for a rattle at idle and judder pulling away.
If it needs doing: Clutch and dual-mass flywheel, about £650–£1,200. ClickMechanic
- Cars registered 2007–2013 · Automatic
Harsh 7G-Tronic automatic
Later automatics can change gear harshly, and repairs are expensive.
At the viewing: Check changes are smooth from cold and at low speed.
If it needs doing: Gearbox sensor or solenoid, about £200–£500. ClickMechanic
- Cars registered 2022–2025 · All engines
Poor reliability record
In What Car?'s survey, 43% of these C-Classes had a fault, with problems in the air con, engine, fuel system, gearbox and electrics. Many left the car undriveable.
At the viewing: Check every warning light goes out, and test the air con and all the electrics.
- Cars registered 2014–2021 · Automatic
Automatic gearbox behaviour
Some automatics shift inconsistently.
At the viewing: Drive through every gear at different speeds. Any odd or jerky changes should be priced in or a reason to walk away.
- Cars registered 2007–2013 · Petrol
Water pump and sensors (petrol)
Water pumps can leak, and air flow or crankshaft sensors cause rough running.
At the viewing: Look for coolant leaks and check it idles smoothly.
If it needs doing: Water pump, about £115–£375. ClickMechanic
Common Mercedes-Benz C-Class MOT failures to check
Parts flagged at MOT well above the usual rate for cars the same age, in more than one year. From the DVSA’s results for every MOT done in Great Britain during 2025.
Ball joint
up to 6.3× usualStands out on cars registered in 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 and 2021.
Rough price £60–£150 (one joint) ClickMechanicAt the viewing: Listen for knocking over bumps and check the rubber boots behind the wheels aren't split.
Wheel bearings
up to 4.5× usualStands out on cars registered in 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 and 2014.
Rough price £120–£300 (one bearing) ClickMechanicAt the viewing: Listen for a hum or growl that changes as you steer at speed.
Link ball joint covers
up to 3.9× usualStands out on cars registered in 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 and 2014.
Rough price £60–£150 (one joint) ClickMechanicAt the viewing: Listen for knocking over bumps and check the rubber boots behind the wheels aren't split.
Sub-frame
up to 3.8× usualStands out on cars registered in 1997, 1998, 1999, 2001, 2002, 2003, 2004 and 2005.
Rough price £300–£1,000 our estimateAt the viewing: Look underneath at the frame the suspension bolts to. Flaky rust or holes are expensive to fix.
Side repeaters
up to 6.2× usualStands out on cars registered in 1997, 1998, 1999, 2000, 2002, 2007 and 2008.
Rough price £10–£80 our estimateAt the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.
Rigid brake pipes
up to 3.9× usualStands out on cars registered in 2007, 2008, 2009, 2010, 2011, 2012 and 2013.
Rough price £100–£400 our estimateAt the viewing: Ask to see underneath, or check the MOT advisories: corroded brake or fuel pipes get worse every year and fail the MOT when they do.
Mercedes-Benz C-Class MOT pass rate by year
Of the years since 2005 with plenty of MOT tests, the 2010 Mercedes-Benz C-Class did best (66% passed first time, 7 points above all 2010 cars) and the 2022 did worst (89%, 0 points above all 2022 cars). Older cars fail more, so compare each year with all cars registered the same year.
| Year | Pass first time | All cars that year | MOT tests |
|---|---|---|---|
| 2023 | 94% | 92% +2 | 355 (small sample) |
| 2022 | 89% | 89% +0 | 4,604 |
| 2021 | 87% | 87% +0 | 5,709 |
| 2020 | 86% | 86% +0 | 9,919 |
| 2019 | 86% | 84% +2 | 24,634 |
| 2018 | 84% | 81% +3 | 28,346 |
| 2017 | 82% | 78% +4 | 39,535 |
| 2016 | 80% | 75% +5 | 36,616 |
| 2015 | 78% | 72% +6 | 34,042 |
| 2014 | 75% | 69% +6 | 25,210 |
| 2013 | 70% | 66% +4 | 23,494 |
| 2012 | 67% | 63% +4 | 25,753 |
| 2011 | 67% | 61% +6 | 18,838 |
| 2010 | 66% | 59% +7 | 12,845 |
| 2009 | 64% | 58% +6 | 12,668 |
| 2008 | 64% | 57% +7 | 13,214 |
| 2007 | 62% | 57% +5 | 11,454 |
| 2006 | 59% | 57% +2 | 8,786 |
| 2005 | 60% | 58% +2 | 7,282 |
| 2004 | 58% | 58% +0 | 5,380 |
| 2003 | 59% | 59% +0 | 3,648 |
| 2002 | 64% | 60% +4 | 2,021 |
| 2001 | 63% | 61% +2 | 1,080 |
| 2000 | 67% | 63% +4 | 523 |
| 1999 | 68% | 65% +3 | 674 |
| 1998 | 71% | 66% +5 | 747 |
| 1997 | 68% | 67% +1 | 611 |
| 1996 | 73% | 67% +6 | 368 (small sample) |
| 1995 | 72% | 67% +5 | 268 (small sample) |
| 1994 | 75% | 69% +6 | 222 (small sample) |
Questions to ask the seller before buying a Mercedes-Benz C-Class
Ask before you travel to see it. A seller who knows the car will have answers, and receipts.
- Has the fuel pump recall been done?
- Have there been any AdBlue or particulate filter warnings?
- Have the injectors or seals been replaced?
- Have the clutch and flywheel been replaced?
- Has the gearbox been serviced?
- Has the water pump been replaced?
Looking at a Mercedes-Benz C-Class?
Check the actual car: its own MOT history, whether it already shows these weak spots and what to ask the seller. Free, no sign-up.
Where this comes from: MOT figures are the DVSA’s anonymised results for every MOT test done in Great Britain during 2025, grouped by the year each car was first registered. How many are on the road is from the Department for Transport’s vehicle licensing statistics. Known faults are from UK buying guides, in our own words, with links. How we score