The MOT Files

Known faults, from the test record

Mercedes-Benz S-Class common problems

What fails on the Mercedes-Benz S-Class at MOT, which parts are behind it, and how each model year compares. From 25,269 DVSA test records.

Data updated

Quick answer

The Mercedes-Benz S-Class's most common MOT problems are tyres, suspension bushes, parking brake, recorded in 42.4%, 37.9% and 13.0% of failed tests respectively. By model year, 2018 cars pass most often (90.5%) and 2007 cars least (75.6%), 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 S-Class 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 25,269 cars.

By component

What wears out on a S-Class

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

    42.4% 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.

    • “Tyre tread depth not in accordance with the requirements” — explained16.9%
    • “A tyre cords visible or damaged” — explained10.7%
    • “A tyre seriously damaged” — explained8.8%
    • “A tyre seriously damaged” — explained3.4%

    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

    37.9% 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” — explained24.7%
    • “A suspension pin, bush or joint excessively worn” — explained7.7%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained5.5%

    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.Parking brake

    13.0% 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” — explained6.2%
    • “Parking brake efficiency less than 50% of the required value” — explained3.9%
    • “Parking brake inoperative on one side” — explained3.0%

  4. 4.Wiper blades and washers

    13.0% of failed tests

    Rubber blades harden and split within a year or two; washer jets block and pumps fail.

    • “Wiper blade missing or obviously not clearing the windscreen” — explained5.5%
    • “Windscreen washers not working or not providing sufficient fluid to clear the windscreen” — explained3.9%
    • “Windscreen washers not working or not providing sufficient fluid to clear the windscreen” — explained3.6%

    Across all cars, wiper blades and washers 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 wiper blades and washers last

  5. 5.Bulbs and lamps

    11.6% of failed tests

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

    • “A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning” — explained3.1%
    • “A direction indicator lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning” — explained3.1%
    • “A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED” — explained2.4%
    • “An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning” — explained1.9%

    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

  6. 6.Engine management

    8.9% 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” — explained5.2%
    • “Engine MIL illuminated indicating a malfunction” — explained3.7%

  7. 7.Brake pads and shoes

    7.5% 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” — explained6.2%
    • “Brake lining or pad worn down to wear indicator” — explained1.4%

    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.Brake pipes

    7.2% 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” — explained7.2%

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

By registration year

S-Class problems by year

MOT pass rate for Mercedes-Benz S-Class 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 2014, up 7.5 points, is larger than wear explains and most likely marks a change in the cars themselves.

200776%
201280%+4.5
201488%+7.5
201587%−0.8
201686%−1.1
201787%+1.4
201890%+3.3
201990%−0.0

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 S-Class owners about

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

Go deeper

The rest of the S-Class file

Common questions

What are the most common problems with a Mercedes-Benz S-Class?
Going by what fails the MOT, tyres (recorded in 42.4% of failed tests), suspension bushes (recorded in 37.9% of failed tests), and parking brake (recorded in 13.0% of failed tests). These are the items testers actually record across 25,269 tests, not reports from owners, so they describe what goes wrong at the point where it has to be fixed.
Which Mercedes-Benz S-Class year is the most reliable?
By MOT pass rate, Mercedes-Benz S-Class cars registered in 2018 do best at 90.5% and 2007 cars do worst at 75.6%. 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 2014, up 7.5 points on 2013.
Is the Mercedes-Benz S-Class reliable?
Adjusted for the age and mileage of the cars tested, the Mercedes-Benz S-Class passes 84.7% 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 S-Class?
Start with what fails most: tyres, suspension bushes, wiper blades and washers. 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