Used car guide

1999 Mercedes-Benz SLK: common problems and what to check

What gets flagged at MOT on 1999 Mercedes-Benz SLKs, from 1,189 tests in 2025, plus known faults and what to look at before you buy one.

1,189MOT tests in 2025
71%pass first time (all 1999 cars: 65%)
3,200typical miles a year
2.7×the usual rate for sub-frame

What stands out

Parts flagged at MOT more often on 1999 Mercedes-Benz SLKs than on all cars registered in 1999.

  • Sub-frame2.7× usual
    Mercedes-Benz SLK
    9.6% All 1999 cars
    3.5%

    Failed outright at MOT: 0.2%, against 0.2% of all 1999 cars. The rest were advisories or minor defects.

    Rough price £300–£1,000 our estimate

    At the viewing: Look underneath at the frame the suspension bolts to. Flaky rust or holes are expensive to fix.

  • Side repeaters4.5× usual
    Mercedes-Benz SLK
    5.4% All 1999 cars
    1.2%

    Failed outright at MOT: 2.2%, against 0.7% of all 1999 cars. The rest were advisories or minor defects.

    Rough price £10–£80 our estimate

    At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.

  • Transmission oil leaks2.9× usual
    Mercedes-Benz SLK
    6.6% All 1999 cars
    2.3%

    Failed outright at MOT: 0.1%, against 0% of all 1999 cars. The rest were advisories or minor defects.

    Rough price £80–£600 our estimate

    At the viewing: Look under the engine and where the car is usually parked for fresh oil. Ask whether the leak has been looked at.

Better than most

Engine oil leaks: 5% here, against 15.7% of all 1999 cars. Suspension arm bushes and joints: 2.2% here, against 5.6% of all 1999 cars.

By area

The share of 1999 Mercedes-Benz SLK MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Brakes
    34% of testsRough price £150–£350

    At the viewing: Look for a lip on the disc edges and feel for judder or pulling when braking firmly from about 40mph.

  • Lights and electrics
    33% of testsRough price £10–£80

    At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.

  • Suspension
    28% of testsRough price £120–£400

    At the viewing: Listen for knocks over speed bumps, and look behind each front wheel for a snapped coil spring.

  • Tyres
    23% of testsRough price £70–£150

    At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.

  • Oil and fluid leaks
    12% of testsRough price £80–£600

    At the viewing: Look under the engine and on the ground where the car is usually parked for fresh oil or fluid.

  • Wipers, windscreen and mirrors
    11% of testsRough price £15–£250

    At the viewing: Check for chips in the driver's view, and test the wipers and washers.

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Other years

YearMOT testsMost flagged
20161,248Tyres 31%
20154,852Tyres 30%
20144,786Tyres 31%
20134,481Tyres 31%
20125,482Tyres 30%
20112,481Brakes 30%
20102,039Brakes 31%
20092,444Suspension 33%
20083,124Suspension 35%
20073,390Suspension 37%
20063,487Suspension 36%
20054,447Suspension 36%
20042,774Suspension 38%
20031,531Lights and electrics 35%
20021,637Brakes 35%
20011,856Brakes 33%
20001,515Lights and electrics 35%
1998889Suspension 33%
1997577Lights and electrics 36%

Where this comes from: the DVSA's anonymised results for every MOT test in Great Britain in 2025, counting tests of 1999 Mercedes-Benz SLKs registered in 1999. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score