1998 Mercedes-Benz SLK — MOT failures & pass rate
The 1998 Mercedes-Benz SLK passed 79.1% of its 7,208 recorded MOT tests. Coupes & convertibles of a similar age fail at 21.7%, so the 1998 SLK sits squarely on the average. Failures cluster in lighting & signalling, brakes and suspension.
What the MOT record shows
Lighting & signalling dominates the failure mix at 17.0% of all tests — 10.6 points clear of brakes, so it is the first thing to check.
At component level the recurring items are headlamp aim, stop lamp and headlamp — headlamp aim alone was recorded 493 times.
Condition tracks the odometer closely. Failures run at 9.8% in the 0-30k band and 31.0% in the 150k+ band, a 21.2-point spread — more than double.
Advisories point at the next bill rather than this one: brakes was flagged on 31.6% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 17.0% | 1,222 |
| 2 | Brakes | 6.4% | 461 |
| 3 | Suspension | 5.4% | 386 |
| 4 | Visibility | 4.8% | 345 |
| 5 | Tyres | 3.8% | 275 |
| 6 | Body, structure & corrosion | 3.0% | 218 |
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 | 493 |
| 2 | Stop lamp | 445 |
| 3 | Headlamp | 307 |
| 4 | Catalyst emissions | 264 |
| 5 | Rigid brake pipes | 238 |
| 6 | Wipers | 226 |
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 | 31.6% | 2,276 |
| 2 | Suspension | 28.9% | 2,080 |
| 3 | Tyres | 23.6% | 1,699 |
| 4 | Lighting & signalling | 14.7% | 1,062 |
| 5 | Emissions & environmental | 11.9% | 857 |
| 6 | Other defects | 9.6% | 689 |
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 | 276 | 9.8% |
| 30-60k | 1,141 | 12.9% |
| 60-90k | 2,167 | 19.2% |
| 90-120k | 2,274 | 23.9% |
| 120-150k | 995 | 26.3% |
| 150k+ | 352 | 31.0% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,921 | 21.3% |
| 2022 | 1,648 | 20.5% |
| 2023 | 1,377 | 19.8% |
| 2024 | 1,233 | 22.1% |
| 2025 | 1,029 | 20.6% |
What to check before buying a 1998 SLK
On a 1998 SLK, lighting & signalling is what the MOT record says goes wrong most — it appeared in 17.0% of tests. Check these areas before you commit.
- Lighting & signalling (17.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- 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.
- Suspension (5.4% 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.
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 SLKs pass their MOT?
79.1% of the 7,208 1998 Mercedes-Benz SLK MOT tests in this dataset passed — a 20.9% fail rate.
What is the most common MOT failure on a 1998 Mercedes-Benz SLK?
Lighting & signalling, recorded in 17.0% of tests, followed by brakes (6.4%).
Does the 1998 SLK get worse with mileage?
Its MOT fail rate rises from 9.8% in the 0-30k band to 31.0% in the 150k+ band.
Methodology & source. Based on 7,208 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.