Model Reports 4 min read Updated 18 Oct 2026

Porsche Boxster 2004: reliability & common MOT faults

In 2025, 76 in every 100 first MOTs on a 2004 Porsche Boxster were passes. Most common reason for a fail: Petrol emissions (with catalyst).

Summary

The 2004 Porsche Boxster follows the pattern of the model years either side.

At a glance

How 1,901 first tests went in 2025.

Passed first time
76 in every 100
Did not pass first time
24 in every 100465 failed first-attempt tests
The typical car
21 yearsabout 77,031 miles
First tests counted
1,901

What failed most often

  1. Petrol emissions (with catalyst)32 in every 100 failed tests

How we count this. Data: UK MOT open data, 2025. Only Class 4 cars on their first MOT of the year are counted. A car that fails and is fixed at the test station still counts as a fail in the first-attempt rate. These are raw results, not adjusted for age, mileage, or peer mix. The MOT does not test engine or gearbox internals.

Note:

These are patterns across 2004 Porsche Boxster vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.

Noise, emissions and leaks

One fault: petrol emissions (with catalyst), 5.3 times as often as on similar cars.

Figures below are measured across the 464 of 465 failed first attempts (99.8%) that recorded an odometer reading in 2025. Mileage is needed to compare like with like.

We only list faults with at least 20 failures and a rate of about 2.0 times that of similar cars, which keeps one-off results out of the list.

Petrol emissions (with catalyst)

Failed on 148 first tests5.3 times as often as similar carsStrong evidence

What it means

Emissions levels over the manufacturer's specified limits are Major, as are levels over default limits, which apply when no exact match is found for the vehicle. Dense blue or clearly visible black smoke at idle, held for a set period, is Major, except for certain older vehicles and two stroke engines where smoke is unavoidable. An induction or exhaust leak that could affect emissions levels is Major too.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Brakes

One fault: rigid brake pipes, 4.2 times as often as on similar cars.

Rigid brake pipes

Failed on 20 first tests4.2 times as often as similar carsPossible evidence

What it means

Chafing, corrosion or damage to a rigid brake pipe justifies rejection once its wall thickness is reduced by a set amount, although DVSA accepts this is not easy to determine. If a tester is not sure, the benefit of the doubt applies. A leaking pipe or connection is graded Dangerous on a hydraulic system and Major on an air system.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 39 first tests, 2.1 times as often as on similar cars.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.

Suspension

One fault: coil spring (front), 2.0 times as often as on similar cars.

Coil spring (front)

Failed on 32 first tests2.0 times as often as similar carsPossible evidence

What it means

A missing bump stop rubber is not a reason to fail a coil spring. When the vehicle is jacked and lowered, a spring that does not correctly locate as the suspension returns to its normal running position is rejected as insecurely attached. A missing spring is Major, and graded Dangerous where directional control is affected.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Advisories

Other things testers noted as worn or close to failing, more often than on similar cars.

An advisory is a note from the tester about something that has not failed yet. It is an early warning, not a fail. Advisories for the faults above are shown with those faults.

Rigid brake pipes (front)

Noted on 78 first tests2.4 times as often as similar carsElevated evidence

Brake discs (rear)

Noted on 55 first tests2.0 times as often as similar carsWear pattern

Data: UK MOT open data, 2025. Counts cover advisories recorded on failed first tests only, compared with cars of the same age and mileage.

MOT pass rates

How first tests ended, and how the pass rates are counted.

Passed first time
76in every 100
Passed on the first test.
Fixed at the station
3in every 100
Failed, then fixed at the test station the same day.
Failed
21in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 75.5% of 1,901 first tests (2025): only cars that passed first time count. Official-style pass 79.3%: cars fixed at the test station also count as a pass. The 3 fixed and the 21 not fixed make the 24 in every 100 that did not pass first time.

Same model, other years

Passed first time in every 100, all tested in 2025.

40608010020002004201020152020Older carsNewer cars
4060801002000200420102020Newer cars

Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 75 in every 100 passed first time.

YearPassed first timeFirst tests
199774 in every 100352
199875 in every 100684
199972 in every 100958
200072 in every 1001,750
200174 in every 1001,917
200273 in every 1001,967
200373 in every 1002,260
2004 This car76 in every 1001,901
200580 in every 1003,065
200682 in every 1001,763
200784 in every 1001,524
200886 in every 1001,027
200988 in every 100816
201089 in every 100779
201188 in every 100743
201290 in every 1001,061
201392 in every 1001,219
201491 in every 1001,156
201591 in every 1001,033
201694 in every 1001,173
201792 in every 100940
201894 in every 100962
201994 in every 100850
202093 in every 100425
202196 in every 100336

FAQs

Short answers about how to read this model-year guide.

The 2004 Porsche Boxster follows the pattern of the model years either side. Its main cause of failure was Petrol emissions (with catalyst), about 32 in every 100 failed tests. In 2025, 75.5% of 1,901 first MOTs on the 2004 Porsche Boxster passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 79.3%. Among 465 failed first-attempt MOT tests (test year 2025), Petrol emissions (with catalyst) appears more often than on similar cars (31.9% of those tests; 148 observed failures; about 5.3× more often than similar cars). There is no single reliability score here; this is a pre-purchase checklist built from DVSA open data, not a guarantee for any individual car.
Ranked by how often they were actually recorded, the items that most often failed a 2004 Porsche Boxster at the first attempt were Petrol emissions (with catalyst) (31.9%), each as a share of the year's failed first attempts. That is what goes wrong most often on the car. The common faults table shows a different measure: faults that are unusual compared with similar cars.
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Petrol emissions (with catalyst) (31.9% of those tests; 148 observed failures; about 5.3× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Petrol emissions (with catalyst) shows up more often than on similar cars (31.9% of those tests; 148 observed failures; about 5.3× more often than similar cars). That does not prove a design fault. Age, mileage, and how the car was used still matter. Treat it as a pre-purchase checkpoint, not a manufacturer service bulletin.
Common MOT problem areas for the 2004 Porsche Boxster include Petrol emissions (with catalyst), Rigid brake pipes, Coil spring (front). These are the faults that stand out compared with similar cars, not a complete list of what can go wrong on any individual car.
Advisories flag issues noted at the test and are not a fail rate. We show advisory patterns that appear more often than on similar cars among failed first-attempt tests, separate from common failure rows. Use them as early-warning checks, not as a pass/fail score.
This page highlights MOT failure patterns for the 2004 Porsche Boxster (registration year) using UK DVSA open data for the selected test year. Patterns are compared with cars of a similar age and mileage. It is a buyer checklist from MOT defect statistics, not a full service history or manufacturer service-bulletin list.
No. MOT tests do not cover engine internals, gearboxes, or many electronic modules. Patterns here come from MOT defect statistics only and should not be read as engine or gearbox reliability scores.

About this data

How this page is built and what it can (and can't) say.

These figures come from UK MOT open data for this model year. We surface common failure patterns against similar cars, not a full reliability score, and not a pass/fail verdict on any individual vehicle.

2024 2025

What we include

UK Class 4 cars only. Normal MOT tests (not retests); first test per vehicle per calendar year; results pass, PRS, or fail.

Same-day repairs

PRS means the car failed items that were fixed at the test station and then passed the same day. We count PRS as a first-attempt fail in headline rates so same-day repairs do not hide problems.

How we compare

We compare this model year with other Class 4 cars of similar age and mileage in the same test year. This model family is left out of the peer group so the car is not measured against itself.

What this does not cover

  • MOTs do not cover engine internals, gearboxes, or many electronics; this is not a full reliability score.
  • Common faults come from MOT defect stats, not manufacturer TSBs or recalls.
  • Age and mileage matching reduces, but does not remove, differences in how cars were used and maintained.
  • If the data for a car is too thin to say anything useful, we say so rather than guess.

Contains public sector information licensed under the Open Government Licence v3.0.

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