The MOT Files

Known faults, from the test record

Mercedes-Benz CLS common problems

What fails on the Mercedes-Benz CLS at MOT, which parts are behind it, and how each model year compares. From 22,073 DVSA test records.

Data updated

Quick answer

The Mercedes-Benz CLS's most common MOT problems are tyres, suspension bushes, coil springs, recorded in 56.2%, 27.4% and 18.4% of failed tests respectively. By model year, 2019 cars pass most often (82.7%) and 2007 cars least (67.6%), 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 CLS 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 22,073 cars.

By component

What wears out on a CLS

Failure items grouped by the part behind them, with the share of failed Mercedes-Benz CLS 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

    56.2% 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” — explained16.8%
    • “Tyre tread depth not in accordance with the requirements” — explained16.4%
    • “A tyre seriously damaged” — explained10.3%
    • “A tyre seriously damaged” — explained6.1%

    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

    27.4% 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” — explained10.1%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained6.2%
    • “A suspension pin, bush or joint excessively worn” — explained4.1%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained3.3%

    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

    18.4% 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” — explained18.4%

    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.Brake pipes

    15.7% of failed tests

    Steel pipes under the car corrode from salt and moisture, fastest on cars kept outside in wet or coastal areas; failure is for excessive corrosion or damage.

    • “Brake pipe damaged or excessively corroded” — explained14.5%
    • “Leaking brake pipe or connection on a hydraulic system” — explained1.2%

    Across all cars, brake pipes failures climb from nothing between three and fifteen years, peaking at 15+ years. How long brake pipes last

  5. 5.Wheels and fixings

    8.0% 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” — explained6.1%
    • “A wheel with a loose or missing wheel nut, bolt or stud” — explained1.9%

  6. 6.Parking brake

    7.6% of failed tests

    Cables stretch and seize, rear shoes and adjusters wear; efficiency is measured on the roller tester against the vehicle's weight.

    • “Parking brake efficiency below minimum requirement” — explained4.2%
    • “Parking brake inoperative on one side” — explained1.9%
    • “Parking brake efficiency less than 50% of the required value” — explained1.5%

  7. 7.Engine management

    7.0% 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” — explained4.4%
    • “Engine MIL illuminated indicating a malfunction” — explained2.6%

  8. 8.Bulbs and lamps

    6.4% of failed tests

    Filament bulbs simply expire; the cheapest and most avoidable failure on the test, and one of the most recorded.

    • “A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED” — explained2.2%
    • “A direction indicator lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning” — explained2.2%
    • “A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning” — explained2.0%

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

By registration year

CLS problems by year

MOT pass rate for Mercedes-Benz CLS 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 2011, up 5.3 points, is larger than wear explains and most likely marks a change in the cars themselves.

200670%
200768%−2.9
200869%+1.1
201174%+5.3
201274%−0.2
201372%−1.6
201475%+2.5
201579%+4.0
201680%+1.0
201780%+0.3
201983%+2.8

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 CLS owners about

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

Go deeper

The rest of the CLS file

Common questions

What are the most common problems with a Mercedes-Benz CLS?
Going by what fails the MOT, tyres (recorded in 56.2% of failed tests), suspension bushes (recorded in 27.4% of failed tests), and coil springs (recorded in 18.4% of failed tests). These are the items testers actually record across 22,073 tests, not reports from owners, so they describe what goes wrong at the point where it has to be fixed.
Which Mercedes-Benz CLS year is the most reliable?
By MOT pass rate, Mercedes-Benz CLS cars registered in 2019 do best at 82.7% and 2007 cars do worst at 67.6%. 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 2011, up 5.3 points on 2010.
Is the Mercedes-Benz CLS reliable?
Adjusted for the age and mileage of the cars tested, the Mercedes-Benz CLS passes 76.4% of MOTs against a national 72.3%. 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 CLS?
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