The MOT Files

Known faults, from the test record

Porsche Cayman common problems

What fails on the Porsche Cayman at MOT, which parts are behind it, and how each model year compares. From 14,702 DVSA test records.

Data updated

Quick answer

The Porsche Cayman's most common MOT problems are tyres, bulbs and lamps, brake pipes, recorded in 37.0%, 17.9% and 15.7% of failed tests respectively. By model year, 2019 cars pass most often (94.5%) and 2006 cars least (79.3%), 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 Porsche Cayman 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 14,702 cars.

By component

What wears out on a Cayman

Failure items grouped by the part behind them, with the share of failed Porsche Cayman 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

    37.0% 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” — explained18.4%
    • “A tyre seriously damaged” — explained7.4%
    • “A tyre cords visible or damaged” — explained4.8%
    • “A tyre seriously damaged” — explained4.0%

    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.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” — explained12.8%
    • “Stop lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning” — explained2.2%
    • “A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED” — explained1.7%
    • “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” — explained1.2%

    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

  3. 3.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” — explained13.3%
    • “Leaking brake pipe or connection on a hydraulic system” — explained2.4%

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

  4. 4.Catalytic converter and emissions

    12.3% 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” — explained10.0%
    • “Emissions levels exceed the manufacturer's specified limits” — explained2.3%

  5. 5.Headlamp aim

    12.0% 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” — explained5.7%
    • “The aim of a headlamp is not within limits laid down in the requirements” — explained3.9%
    • “The aim of a headlamp is not within limits laid down in the requirements” — explained2.4%

  6. 6.Wiper blades and washers

    11.2% 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” — explained5.8%
    • “Windscreen washers not working or not providing sufficient fluid to clear the windscreen” — explained2.9%
    • “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

  7. 7.Coil springs

    9.8% 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” — explained9.8%

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

  8. 8.Parking brake

    9.4% 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” — explained4.5%
    • “Parking brake inoperative on one side” — explained2.5%
    • “Parking brake lever has excessive movement indicating incorrect adjustment” — explained1.2%
    • “Parking brake efficiency less than 50% of the required value” — explained1.2%

By registration year

Cayman problems by year

MOT pass rate for Porsche Cayman 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 2013, up 9.5 points, is larger than wear explains and most likely marks a change in the cars themselves.

200679%
200781%+1.3
201390%+9.5
201491%+1.0
201593%+2.2
201694%+0.6
201894%−0.1
201995%+0.7

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 Cayman owners about

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

Go deeper

The rest of the Cayman file

Common questions

What are the most common problems with a Porsche Cayman?
Going by what fails the MOT, tyres (recorded in 37.0% of failed tests), bulbs and lamps (recorded in 17.9% of failed tests), and brake pipes (recorded in 15.7% of failed tests). These are the items testers actually record across 14,702 tests, not reports from owners, so they describe what goes wrong at the point where it has to be fixed.
Which Porsche Cayman year is the most reliable?
By MOT pass rate, Porsche Cayman cars registered in 2019 do best at 94.5% and 2006 cars do worst at 79.3%. 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 2013, up 9.5 points on 2012.
Is the Porsche Cayman reliable?
Adjusted for the age and mileage of the cars tested, the Porsche Cayman passes 87.2% 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 Porsche Cayman?
Start with what fails most: tyres, bulbs and lamps, brake pipes. 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