Mercedes-Benz C320d — MOT pass rate & failures
5,464 MOT tests on the Mercedes-Benz C320d (2000–2015) give a 75.5% pass rate. That is 6.6 percentage points worse than the 17.9% fail rate across all Mercedes-Benz C-Class versions, so the C320d is a weaker pick within the range. Failures concentrate in suspension, lighting & signalling and brakes.
What the MOT record shows
At component level the recurring items are ball joint, rigid brake pipes and coil spring — ball joint alone was recorded 408 times.
Condition tracks the odometer closely. Failures run at 17.9% in the 30-60k band and 27.4% in the 150k+ band, a 9.5-point spread.
Brakes is the most common advisory, noted on 36.0% of tests — work that passed today but is likely due soon.
The trend is improving — the fail rate fell from 25.1% in 2021 to 23.1% in 2025, as the worst-kept examples leave the fleet.
How it compares
By model year
| Year | Tests | Pass rate | Fail rate |
|---|---|---|---|
| 2005 | 473 | 72.3% | 27.7% |
| 2006 | 1,080 | 73.9% | 26.1% |
| 2007 | 997 | 76.8% | 23.2% |
| 2008 | 1,790 | 76.6% | 23.4% |
| 2009 | 992 | 75.3% | 24.7% |
| 2010 | 101 | 77.2% | 22.8% |
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Suspension | 13.6% | 745 |
| 2 | Lighting & signalling | 9.4% | 514 |
| 3 | Brakes | 8.5% | 464 |
| 4 | Tyres | 5.9% | 324 |
| 5 | Emissions & environmental | 5.5% | 301 |
| 6 | Visibility | 2.9% | 157 |
| 7 | Body, structure & corrosion | 1.6% | 87 |
| 8 | Steering | 1.4% | 77 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Ball joint | 408 |
| 2 | Rigid brake pipes | 321 |
| 3 | Coil spring | 266 |
| 4 | Headlamp aim | 229 |
| 5 | Tread depth | 199 |
| 6 | Malfunction indicator lamp | 146 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 36.0% | 1,967 |
| 2 | Suspension | 30.5% | 1,666 |
| 3 | Tyres | 26.3% | 1,435 |
| 4 | Emissions & environmental | 13.4% | 733 |
| 5 | Other defects | 7.5% | 408 |
| 6 | Lighting & signalling | 7.0% | 381 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 30-60k | 279 | 17.9% |
| 60-90k | 921 | 22.5% |
| 90-120k | 1,615 | 23.5% |
| 120-150k | 1,473 | 25.7% |
| 150k+ | 1,148 | 27.4% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,369 | 25.1% |
| 2022 | 1,260 | 24.4% |
| 2023 | 1,140 | 25.4% |
| 2024 | 912 | 23.7% |
| 2025 | 783 | 23.1% |
What to check before buying a Mercedes-Benz C320d
Focus on the areas it most often fails on — and remember MOT data covers testable defects only, not engine or gearbox health.
- Suspension (13.6% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
- Lighting & signalling (9.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (8.5% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How reliable is the Mercedes-Benz C320d at MOT time?
75.5% of the 5,464 Mercedes-Benz C320d MOT tests in this dataset passed — a 24.5% fail rate, worse than the 17.9% average across all C-Class versions.
What is the most common MOT failure on a Mercedes-Benz C320d?
Suspension, recorded in 13.6% of tests, followed by lighting & signalling (9.4%).
Does the C320d get worse with mileage?
Its MOT fail rate rises from 17.9% in the 30-60k band to 27.4% in the 150k+ band.
Methodology & source. Based on 5,464 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.