2004 Mercedes-Benz Sl — MOT failures & pass rate
Across 10,904 MOT tests, the 2004 Mercedes-Benz Sl recorded an 86.0% pass rate. That is 8.4 percentage points better than coupes & convertibles of a similar age, which fail at 22.4%. Failures cluster in suspension, brakes and lighting & signalling.
What the MOT record shows
No single area dominates — suspension (6.3%) and brakes (4.5%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are coil spring, ball joint and headlamp aim — coil spring alone was recorded 261 times.
A 150k+ example is materially riskier than a 0-30k one: 19.8% versus 6.8%.
Advisories point at the next bill rather than this one: brakes was flagged on 22.6% of tests without failing them.
The trend is improving — the fail rate fell from 15.5% in 2021 to 13.1% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Suspension | 6.3% | 684 |
| 2 | Brakes | 4.5% | 485 |
| 3 | Lighting & signalling | 4.0% | 436 |
| 4 | Tyres | 3.3% | 364 |
| 5 | Visibility | 1.8% | 198 |
| 6 | Emissions & environmental | 1.1% | 122 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Coil spring | 261 |
| 2 | Ball joint | 247 |
| 3 | Headlamp aim | 232 |
| 4 | Rigid brake pipes | 200 |
| 5 | Shock absorbers | 162 |
| 6 | Ball joint dust cover | 159 |
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 | 22.6% | 2,464 |
| 2 | Tyres | 19.1% | 2,085 |
| 3 | Suspension | 15.2% | 1,656 |
| 4 | Other defects | 4.8% | 520 |
| 5 | Lighting & signalling | 4.5% | 496 |
| 6 | Emissions & environmental | 4.5% | 492 |
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 | 665 | 6.8% |
| 30-60k | 2,818 | 10.2% |
| 60-90k | 4,055 | 14.2% |
| 90-120k | 2,297 | 17.4% |
| 120-150k | 814 | 20.3% |
| 150k+ | 227 | 19.8% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 2,426 | 15.5% |
| 2022 | 2,314 | 14.3% |
| 2023 | 2,198 | 13.6% |
| 2024 | 2,033 | 13.3% |
| 2025 | 1,933 | 13.1% |
What to check before buying a 2004 Sl
On a 2004 Sl, suspension is what the MOT record says goes wrong most — it appeared in 6.3% of tests. Check these areas before you commit.
- Suspension (6.3% 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 (4.5% 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.
- Lighting & signalling (4.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
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 Sls pass their MOT?
86.0% of the 10,904 2004 Mercedes-Benz Sl MOT tests in this dataset passed — a 14.0% fail rate.
What is the most common MOT failure on a 2004 Mercedes-Benz Sl?
Suspension, recorded in 6.3% of tests, followed by brakes (4.5%).
Does the 2004 Sl get worse with mileage?
Its MOT fail rate rises from 6.8% in the 0-30k band to 19.8% in the 150k+ band.
Methodology & source. Based on 10,904 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.