The MOT Files

Known faults, from the test record

Ford Mustang common problems

What fails on the Ford Mustang at MOT, which parts are behind it, and how each model year compares. From 12,306 DVSA test records.

Data updated

Quick answer

The Ford Mustang's most common MOT problems are parking brake, tyres, wiper blades and washers, recorded in 51.7%, 36.3% and 19.6% of failed tests respectively. By model year, 2020 cars pass most often (86.7%) and 2016 cars least (81.4%), 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 Ford Mustang 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 12,306 cars.

By component

What wears out on a Mustang

Failure items grouped by the part behind them, with the share of failed Ford Mustang 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.Parking brake

    51.7% 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” — explained21.2%
    • “Parking brake inoperative on one side” — explained14.6%
    • “Parking brake efficiency less than 50% of the required value” — explained10.3%
    • “Parking brake lever has excessive movement indicating incorrect adjustment” — explained4.4%

  2. 2.Tyres

    36.3% 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” — explained17.2%
    • “Tyre tread depth not in accordance with the requirements” — explained9.9%
    • “A tyre seriously damaged” — explained6.2%
    • “A tyre seriously damaged” — explained1.7%

    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

  3. 3.Wiper blades and washers

    19.6% 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” — explained10.1%
    • “Windscreen washers not working or not providing sufficient fluid to clear the windscreen” — explained6.9%
    • “Windscreen washers not working or not providing sufficient fluid to clear the windscreen” — explained2.6%

    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

  4. 4.Bulbs and lamps

    17.9% 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” — explained4.5%
    • “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” — explained2.8%
    • “Lamp emitted colour, position or intensity not in accordance with the requirements” — explained2.6%
    • “A direction indicator 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

  5. 5.Suspension bushes

    8.0% 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” — explained6.4%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained1.6%

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

  6. 6.Headlamp aim

    5.7% of failed tests

    Aim drifts with sagging suspension, a knocked lamp or a botched bulb change; adjustment, not a part.

    • “The aim of a headlamp is not within limits laid down in the requirements” — explained2.6%
    • “The aim of a headlamp is not within limits laid down in the requirements” — explained1.7%
    • “The aim of a headlamp is not within limits laid down in the requirements” — explained1.3%

  7. 7.Registration plates

    5.5% 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” — explained5.5%

  8. 8.Catalytic converter and emissions

    5.4% of failed tests

    Catalysts degrade with age and misfires; a failed emissions reading is usually the catalyst, a lambda sensor or a tired engine.

    • “Lambda coefficient outside the default limits or the range specified by the manufacturer” — explained4.0%
    • “Emissions levels exceed default limits” — explained1.4%

By registration year

Mustang problems by year

MOT pass rate for Ford Mustang 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. No single step here is large enough to point at a generation change.

201681%
201782%+0.7
201884%+1.5
201985%+0.9
202087%+2.1

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 Mustang owners about

Advisories are the same parts a year or two earlier. Share of all Ford Mustang tests carrying an advisory for each.

Go deeper

The rest of the Mustang file

Common questions

What are the most common problems with a Ford Mustang?
Going by what fails the MOT, parking brake (recorded in 51.7% of failed tests), tyres (recorded in 36.3% of failed tests), and wiper blades and washers (recorded in 19.6% of failed tests). These are the items testers actually record across 12,306 tests, not reports from owners, so they describe what goes wrong at the point where it has to be fixed.
Which Ford Mustang year is the most reliable?
By MOT pass rate, Ford Mustang cars registered in 2020 do best at 86.7% and 2016 cars do worst at 81.4%. 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.
Is the Ford Mustang reliable?
Adjusted for the age and mileage of the cars tested, the Ford Mustang passes 80.6% 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 Ford Mustang?
Start with what fails most: tyres, wiper blades and washers, bulbs and lamps. 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