The MOT Files

Known faults, from the test record

Mercedes-Benz SLC common problems

What fails on the Mercedes-Benz SLC at MOT, which parts are behind it, and how each model year compares. From 8,979 DVSA test records.

Data updated

Quick answer

The Mercedes-Benz SLC's most common MOT problems are tyres, suspension bushes, coil springs, recorded in 64.2%, 26.9% and 16.5% of failed tests respectively. By model year, 2018 cars pass most often (88.8%) and 2017 cars least (82.4%), though most of that gap is age. Every figure here is what testers recorded, not what owners reported.

A “common problems” list is usually a forum thread: whoever had the worst day writes the longest post. This one is built the other way, from every Mercedes-Benz SLC that took an MOT last year and what the tester wrote down. It cannot see breakdowns, electrical gremlins or a gearbox that hunts, because the test does not check those. What it can see, it sees across 8,979 cars.

By component

What wears out on a SLC

Failure items grouped by the part behind them, with the share of failed Mercedes-Benz SLC tests recording each. A part can carry several DVSA wordings; they are listed beneath. One failed test often lists several items, so shares do not sum to 100%.

  1. 1.Tyres

    64.2% of failed tests

    Tread wears with every mile and sidewalls age and take kerb damage; the legal minimum is 1.6 mm across the central three-quarters.

    • “A tyre cords visible or damaged” — explained22.5%
    • “A tyre seriously damaged” — explained17.5%
    • “Tyre tread depth not in accordance with the requirements” — explained12.7%
    • “A tyre seriously damaged” — explained6.0%

    Across all cars, tyres failures run at a similar rate at every age, because they are replaced on a cycle rather than wearing out with the car. How long tyres last

  2. 2.Suspension bushes

    26.9% of failed tests

    Rubber bushes in arms and links perish and split with age and load; the most recorded suspension item on the test.

    • “A suspension pin, bush or joint excessively worn” — explained11.1%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained6.1%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained5.3%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained3.0%

    Across all cars, suspension bushes failures climb 20-fold between three and fifteen years, peaking at 15+ years. How long suspension bushes last

  3. 3.Coil springs

    16.5% of failed tests

    Springs fatigue and corrode where the coating chips, then snap, often at the bottom coil; potholes and salt accelerate it.

    • “A spring or spring component fractured or seriously weakened” — explained16.5%

    Across all cars, coil springs failures climb 20-fold between three and fifteen years, peaking at 12–14 years. How long coil springs last

  4. 4.Engine management

    6.5% of failed tests

    The MIL lamp lit is a failure in itself, whatever the stored code; the fault codes section explains what lies behind it.

    • “Engine MIL illuminated indicating a malfunction” — explained4.3%
    • “Engine MIL illuminated indicating a malfunction” — explained2.2%

  5. 5.Wheels and fixings

    6.1% of failed tests

    Rims crack or distort on potholes and kerbs; a missing or loose wheel nut is a fitting error rather than wear.

    • “Any fracture or welding defect on a wheel” — explained4.4%
    • “A wheel with a loose or missing wheel nut, bolt or stud” — explained1.3%
    • “A wheel badly distorted or wear between wheel and hub at spigot mounting” — explained0.4%

  6. 6.Brake and ABS warning lamps

    5.7% of failed tests

    A lit ABS or brake warning lamp fails; commonly a wheel speed sensor or a low fluid level.

    • “Warning device shows system malfunction” — explained5.7%

  7. 7.Brake pads and shoes

    3.8% of failed tests

    Friction material wears with use; the MOT limit is 1.5 mm and a pad that thin is close to metal on metal.

    • “a brake lining or pad worn below 1.5mm” — explained2.8%
    • “Brake lining or pad worn down to wear indicator” — explained1.0%

    Across all cars, brake pads and shoes failures run at a similar rate at every age, because they are replaced on a cycle rather than wearing out with the car. How long brake pads and shoes last

  8. 8.Registration plates

    3.4% of failed tests

    Plates fade, crack and delaminate; non-standard fonts and spacing fail regardless of condition.

    • “Number plate does not conform to the specified requirements” — explained3.4%

By registration year

SLC problems by year

MOT pass rate for Mercedes-Benz SLC cars by the year they were first registered, from years with at least 1,000 tests. Every car in a row is the same age, so the rate is raw. Neighbouring years differ by a year of wear — a step of a point or two is age. The step at 2018, up 6.4 points, is larger than wear explains and most likely marks a change in the cars themselves.

201684%
201782%−1.3
201889%+6.4

Last column: change on the previous year, in points. Years registered within the last three years have not yet been tested and are not shown.

Before it fails

What testers warn SLC owners about

Advisories are the same parts a year or two earlier. Share of all Mercedes-Benz SLC tests carrying an advisory for each.

Go deeper

The rest of the SLC file

Common questions

What are the most common problems with a Mercedes-Benz SLC?
Going by what fails the MOT, tyres (recorded in 64.2% of failed tests), suspension bushes (recorded in 26.9% of failed tests), and coil springs (recorded in 16.5% of failed tests). These are the items testers actually record across 8,979 tests, not reports from owners, so they describe what goes wrong at the point where it has to be fixed.
Which Mercedes-Benz SLC year is the most reliable?
By MOT pass rate, Mercedes-Benz SLC cars registered in 2018 do best at 88.8% and 2017 cars do worst at 82.4%. Most of that ordering is simply age — newer cars pass more — so read the year table for steps larger than a couple of points between neighbouring years; those mark a change in the cars rather than the calendar. The largest such step is at 2018, up 6.4 points on 2017.
Is the Mercedes-Benz SLC reliable?
The Mercedes-Benz SLC passes 85.1% of MOTs unadjusted; its fleet is too narrow in age or mileage for a fair national comparison. An MOT measures roadworthiness on the day rather than breakdowns or running costs, so this is a reliability measure in the narrow sense: how often the car meets the legal standard, and what stops it.
What should I check when buying a used Mercedes-Benz SLC?
Start with what fails most: tyres, suspension bushes, coil springs. Then read the car's own MOT history for advisories carried year to year without repair — the model tells you what to expect, the history tells you whether this owner dealt with it.

Analysis built from DVSA data of