Used car guide

2004 Mercedes-Benz SLK: common problems and what to check

What gets flagged at MOT on 2004 Mercedes-Benz SLKs, from 2,774 tests in 2025, plus known faults and what to look at before you buy one.

2,774MOT tests in 2025
66%pass first time (all 2004 cars: 58%)
3,900typical miles a year
2.6×the usual rate for steering rack

What stands out

Parts flagged at MOT more often on 2004 Mercedes-Benz SLKs than on all cars registered in 2004.

  • Steering rack2.6× usual
    Mercedes-Benz SLK
    4.7% All 2004 cars
    1.8%

    Failed outright at MOT: 3.4%, against 1% of all 2004 cars. The rest were advisories or minor defects.

    Rough price £100–£450 our estimate

    At the viewing: On a straight road the steering wheel should sit straight. Listen for knocks when turning, and check the steering feels even.

Better than most

Engine oil leaks: 7.8% here, against 15.8% of all 2004 cars. Rust around suspension or steering mountings: 1.6% here, against 6.6% of all 2004 cars.

By area

The share of 2004 Mercedes-Benz SLK MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Suspension
    38% 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.

  • Brakes
    33% 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
    28% of testsRough price £10–£80

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

  • Tyres
    26% 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
    10% 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.

  • Exhaust and emissions
    8% of testsRough price £100–£1,200

    At the viewing: Look for black soot in the tailpipe, listen for blowing from the exhaust and check for engine or DPF warning lights.

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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%
20031,531Lights and electrics 35%
20021,637Brakes 35%
20011,856Brakes 33%
20001,515Lights and electrics 35%

Where this comes from: the DVSA's anonymised results for every MOT test in Great Britain in 2025, counting tests of 2004 Mercedes-Benz SLKs registered in 2004. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score