The MOT Files

Known faults, from the test record

London Taxis Int TX4 common problems

What fails on the London Taxis Int TX4 at MOT, which parts are behind it, and how each model year compares. From 10,429 DVSA test records.

Data updated

Quick answer

The London Taxis Int TX4's most common MOT problems are suspension bushes, bulbs and lamps, parking brake, recorded in 95.6%, 30.8% and 22.3% of failed tests respectively. By model year, 2017 cars pass most often (72.5%) and 2014 cars least (64.0%), 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 London Taxis Int TX4 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 10,429 cars.

By component

What wears out on a TX4

Failure items grouped by the part behind them, with the share of failed London Taxis Int TX4 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.Suspension bushes

    95.6% 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” — explained46.0%
    • “A suspension pin, bush or joint excessively worn” — explained20.6%
    • “A suspension joint dust cover missing or no longer prevents the ingress of dirt etc” — explained7.9%
    • “A suspension pin, bush or joint excessively worn” — explained6.1%

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

  2. 2.Bulbs and lamps

    30.8% 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” — explained12.7%
    • “A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED” — explained6.5%
    • “Lamp emitted colour, position or intensity not in accordance with the requirements” — explained6.0%
    • “A rear registration plate lamp or light source missing or inoperative in the case of a single lamp or all lamps” — explained5.7%

    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.Parking brake

    22.3% 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” — explained15.2%
    • “Parking brake efficiency less than 50% of the required value” — explained3.8%
    • “Parking brake inoperative on one side” — explained3.2%

  4. 4.Headlamp aim

    20.7% 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” — explained7.8%
    • “The aim of a headlamp is not within limits laid down in the requirements” — explained6.7%
    • “The aim of a headlamp is not within limits laid down in the requirements” — explained6.3%

  5. 5.Shock absorbers

    11.9% of failed tests

    Seals wear and the damper leaks fluid or loses its action; failure is for a leak or no damping, not for being tired.

    • “A shock absorber bush excessively worn” — explained11.9%

    Across all cars, shock absorbers failures climb 7-fold between three and fifteen years, peaking at 15+ years. How long shock absorbers last

  6. 6.Body and structure

    11.7% of failed tests

    Structural corrosion within 30 cm of a seat belt, suspension or steering mounting fails; it is a disease of age, salt and wet storage.

    • “Vehicle structure corroded to the extent that the rigidity of the assembly is seriously reduced” — explained4.8%
    • “Body, cab or chassis excessively corroded at a mounting point” — explained4.2%
    • “A door will not open using the relevant control or close properly” — explained2.7%

  7. 7.Wheel bearings

    9.5% of failed tests

    Bearings wear with mileage and drone or rumble before they develop the play that fails.

    • “A wheel bearing with excessive play” — explained9.5%

    Across all cars, wheel bearings failures climb 26-fold between three and fifteen years, peaking at 15+ years. How long wheel bearings last

  8. 8.Engine management

    9.1% 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” — explained6.4%
    • “Engine MIL illuminated indicating a malfunction” — explained2.7%

By registration year

TX4 problems by year

MOT pass rate for London Taxis Int TX4 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.

201464%
201568%+3.7
201669%+1.7
201772%+3.0

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 TX4 owners about

Advisories are the same parts a year or two earlier. Share of all London Taxis Int TX4 tests carrying an advisory for each.

Go deeper

The rest of the TX4 file

Common questions

What are the most common problems with a London Taxis Int TX4?
Going by what fails the MOT, suspension bushes (recorded in 95.6% of failed tests), bulbs and lamps (recorded in 30.8% of failed tests), and parking brake (recorded in 22.3% of failed tests). These are the items testers actually record across 10,429 tests, not reports from owners, so they describe what goes wrong at the point where it has to be fixed.
Which London Taxis Int TX4 year is the most reliable?
By MOT pass rate, London Taxis Int TX4 cars registered in 2017 do best at 72.5% and 2014 cars do worst at 64.0%. 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 London Taxis Int TX4 reliable?
The London Taxis Int TX4 passes 67.5% 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 London Taxis Int TX4?
Start with what fails most: suspension bushes, bulbs and lamps, shock absorbers. 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