2004 Mercedes-Benz C-Class — MOT failures & pass rate
55,339 MOT tests on the 2004 Mercedes-Benz C-Class are in this dataset, and 72.0% of them passed. Against executive cars of a similar age (24.3% fail rate), the 2004 C-Class comes out 3.7pp worse. Failures cluster in suspension, lighting & signalling and brakes.
What the MOT record shows
One area stands out: suspension, recorded in 17.5% of tests against 13.4% for the next-worst category.
At component level the recurring items are ball joint, headlamp aim and coil spring — ball joint alone was recorded 5,111 times.
Condition tracks the odometer closely. Failures run at 19.4% in the 0-30k band and 30.4% in the 150k+ band, a 11.0-point spread.
Fuel type barely separates them — petrol fails 27.5% of the time against 29.0% for diesel.
Suspension is the most common advisory, noted on 43.6% of tests — work that passed today but is likely due soon.
The trend is improving — the fail rate fell from 28.6% in 2021 to 26.5% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Suspension | 17.5% | 9,662 |
| 2 | Lighting & signalling | 13.4% | 7,386 |
| 3 | Brakes | 9.0% | 4,998 |
| 4 | Emissions & environmental | 7.3% | 4,028 |
| 5 | Tyres | 5.9% | 3,295 |
| 6 | Visibility | 4.5% | 2,480 |
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 | 5,111 |
| 2 | Headlamp aim | 3,987 |
| 3 | Coil spring | 3,836 |
| 4 | Catalyst emissions | 2,459 |
| 5 | Headlamp | 2,437 |
| 6 | Tread depth | 2,406 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Suspension | 43.6% | 24,128 |
| 2 | Brakes | 36.9% | 20,442 |
| 3 | Tyres | 27.4% | 15,165 |
| 4 | Lighting & signalling | 17.9% | 9,903 |
| 5 | Other defects | 12.4% | 6,855 |
| 6 | Body, structure & corrosion | 11.1% | 6,117 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 516 | 19.4% |
| 30-60k | 3,850 | 20.9% |
| 60-90k | 11,012 | 26.1% |
| 90-120k | 16,075 | 28.2% |
| 120-150k | 13,018 | 29.6% |
| 150k+ | 10,704 | 30.4% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 37,626 | 27.5% |
| Diesel | 17,711 | 29.0% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 15,768 | 28.6% |
| 2022 | 13,175 | 28.2% |
| 2023 | 10,791 | 27.8% |
| 2024 | 8,808 | 27.9% |
| 2025 | 6,797 | 26.5% |
What to check before buying a 2004 C-Class
The failure pattern for this year is specific enough to inspect against: suspension accounted for 17.5% of tests. Start there.
- Suspension (17.5% 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 (13.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (9.0% 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 many 2004 Mercedes-Benz C-Classs pass their MOT?
72.0% of the 55,339 2004 Mercedes-Benz C-Class MOT tests in this dataset passed — a 28.0% fail rate.
What is the most common MOT failure on a 2004 Mercedes-Benz C-Class?
Suspension, recorded in 17.5% of tests, followed by lighting & signalling (13.4%).
Does the 2004 C-Class get worse with mileage?
Its MOT fail rate rises from 19.4% in the 0-30k band to 30.4% in the 150k+ band.
Methodology & source. Based on 55,339 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.