1998 Mercedes-Benz C-Class — MOT failures & pass rate
Across 6,987 MOT tests, the 1998 Mercedes-Benz C-Class recorded an 80.0% pass rate. That is 2.8 percentage points better than executive cars of a similar age, which fail at 22.8%. Failures cluster in lighting & signalling, suspension and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 12.4% of all tests — 4.5 points clear of suspension, so it is the first thing to check.
At component level the recurring items are headlamp aim, component mounting prescribed areas and individual direction indicators — headlamp aim alone was recorded 281 times.
A 150k+ example is materially riskier than a 0-30k one: 25.0% versus 12.8%.
Fuel type barely separates them — petrol fails 19.8% of the time against 21.3% for diesel.
Advisories point at the next bill rather than this one: suspension was flagged on 33.6% of tests without failing them.
The trend is improving — the fail rate fell from 20.9% in 2021 to 18.6% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 12.4% | 870 |
| 2 | Suspension | 8.0% | 557 |
| 3 | Brakes | 6.4% | 448 |
| 4 | Body, structure & corrosion | 4.3% | 298 |
| 5 | Visibility | 3.9% | 272 |
| 6 | Tyres | 3.9% | 272 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 281 |
| 2 | Component mounting prescribed areas | 272 |
| 3 | Individual direction indicators | 272 |
| 4 | Side repeaters | 241 |
| 5 | Catalyst emissions | 238 |
| 6 | Position lamp | 219 |
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 | 33.6% | 2,350 |
| 2 | Brakes | 32.5% | 2,270 |
| 3 | Tyres | 23.5% | 1,642 |
| 4 | Emissions & environmental | 14.6% | 1,020 |
| 5 | Lighting & signalling | 13.6% | 953 |
| 6 | Other defects | 13.0% | 908 |
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 | 94 | 12.8% |
| 30-60k | 520 | 11.2% |
| 60-90k | 1,449 | 16.8% |
| 90-120k | 1,846 | 19.8% |
| 120-150k | 1,665 | 21.9% |
| 150k+ | 1,395 | 25.0% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 6,094 | 19.8% |
| Diesel | 893 | 21.3% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 2,090 | 20.9% |
| 2022 | 1,679 | 20.7% |
| 2023 | 1,321 | 19.1% |
| 2024 | 1,022 | 19.3% |
| 2025 | 875 | 18.6% |
What to check before buying a 1998 C-Class
On a 1998 C-Class, lighting & signalling is what the MOT record says goes wrong most — it appeared in 12.4% of tests. Check these areas before you commit.
- Lighting & signalling (12.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (8.0% 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.
- Brakes (6.4% 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 1998 Mercedes-Benz C-Classs pass their MOT?
80.0% of the 6,987 1998 Mercedes-Benz C-Class MOT tests in this dataset passed — a 20.0% fail rate.
What is the most common MOT failure on a 1998 Mercedes-Benz C-Class?
Lighting & signalling, recorded in 12.4% of tests, followed by suspension (8.0%).
Does the 1998 C-Class get worse with mileage?
Its MOT fail rate rises from 12.8% in the 0-30k band to 25.0% in the 150k+ band.
Methodology & source. Based on 6,987 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.