2003 Mercedes-Benz SLK — MOT failures & pass rate
Across 11,475 MOT tests, the 2003 Mercedes-Benz SLK recorded a 78.6% pass rate. Against coupes & convertibles of a similar age (22.6% fail rate), the 2003 SLK comes out 1.2pp better. Failures cluster in lighting & signalling, suspension and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 15.2% of all tests — 7.9 points clear of suspension, so it is the first thing to check.
At component level the recurring items are stop lamp, headlamp aim and coil spring — stop lamp alone was recorded 741 times.
Condition tracks the odometer closely. Failures run at 9.5% in the 0-30k band and 28.1% in the 150k+ band, a 18.5-point spread — more than double.
Advisories point at the next bill rather than this one: brakes was flagged on 32.8% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 15.2% | 1,745 |
| 2 | Suspension | 7.4% | 845 |
| 3 | Brakes | 7.2% | 823 |
| 4 | Visibility | 4.9% | 560 |
| 5 | Tyres | 4.3% | 495 |
| 6 | Emissions & environmental | 3.7% | 427 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Stop lamp | 741 |
| 2 | Headlamp aim | 734 |
| 3 | Coil spring | 610 |
| 4 | Headlamp | 546 |
| 5 | Position lamp | 408 |
| 6 | Rigid brake pipes | 393 |
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 | 32.8% | 3,764 |
| 2 | Tyres | 24.6% | 2,820 |
| 3 | Suspension | 24.4% | 2,798 |
| 4 | Emissions & environmental | 12.6% | 1,450 |
| 5 | Lighting & signalling | 10.7% | 1,224 |
| 6 | Other defects | 9.5% | 1,092 |
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 | 420 | 9.5% |
| 30-60k | 2,233 | 15.7% |
| 60-90k | 4,233 | 21.1% |
| 90-120k | 3,101 | 24.8% |
| 120-150k | 1,169 | 26.4% |
| 150k+ | 310 | 28.1% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 2,763 | 21.5% |
| 2022 | 2,513 | 20.3% |
| 2023 | 2,311 | 21.8% |
| 2024 | 2,071 | 22.4% |
| 2025 | 1,817 | 21.2% |
What to check before buying a 2003 SLK
On a 2003 SLK, lighting & signalling is what the MOT record says goes wrong most — it appeared in 15.2% of tests. Check these areas before you commit.
- Lighting & signalling (15.2% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (7.4% 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 (7.2% 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 2003 Mercedes-Benz SLKs pass their MOT?
78.6% of the 11,475 2003 Mercedes-Benz SLK MOT tests in this dataset passed — a 21.4% fail rate.
What is the most common MOT failure on a 2003 Mercedes-Benz SLK?
Lighting & signalling, recorded in 15.2% of tests, followed by suspension (7.4%).
Does the 2003 SLK get worse with mileage?
Its MOT fail rate rises from 9.5% in the 0-30k band to 28.1% in the 150k+ band.
Methodology & source. Based on 11,475 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.