Model Reports 8 min read Updated 13 Jul 2026

Mercedes-Benz Sl 2004: reliability & common MOT faults

On the 2004 Mercedes-Benz Sl, MOT failures for Ball joint dust cover (front) and Rigid brake pipes (front) show up more often than on similar cars of the same age and mileage. Figures come from UK DVSA open data for tests in 2025 (292 failed first-attempt tests). Figures are among first-attempt failed MOT tests, not among all tests.

Sample

292 failed first-attempt tests · 1,692 first tests (test year 2025)

Standout pattern

Ball joint dust cover (front) — about 4.3× more often than on similar cars.

What to check

  • Ball joint dust cover (front) — about 4.3× more often than similar cars
  • Rigid brake pipes (front) — about 3.0× more often than similar cars
  • Coil spring (front) — about 3.0× more often than similar cars

Common faults

Failure patterns that show up more often on this registration year than on similar cars.

These MOT failure patterns show up more often on this registration year than on similar cars of the same class, age, and mileage.

Based on 292 failed first-attempt tests in 2025.

Ball joint dust cover (front)

This failure pattern appears about 4.3× more often than on similar cars — recorded on 28 failed first-attempt tests; 9.6% of failed tests for this model year.

Front 28 failures ×4.3 9.6% of failed first tests Possible

Rigid brake pipes (front)

This failure pattern appears about 3.0× more often than on similar cars — recorded on 21 failed first-attempt tests; 7.2% of failed tests for this model year.

Front 21 failures ×3.0 7.2% of failed first tests Possible

No patterns met the strongest callout thresholds on this page; showing the highest-lift rows that still cleared the display floors.

# Fault pattern Location Failures vs similar cars Share of fails Confidence
1 Ball joint dust cover (front)
Suspension > Suspension arms > Ball joint dust cover
 Front 28 ×4.3 9.6% Possible
2 Rigid brake pipes (front)
Brakes > Rigid brake pipes
 Front 21 ×3.0 7.2% Possible
3 Coil spring (front)
Suspension > Springs > Coil springs > Coil spring
 Front 30 ×3.0 10.3% Possible
4 Ball joint (front)
Suspension > Suspension arms > Ball joint
 Front 32 ×2.5 11.0% Possible

Only patterns that clear minimum sample and elevation thresholds are shown (at least 20 failures and about 2.0× more often than similar cars).

Note: Rates and comparisons are among first-attempt failed tests, not all MOTs. Patterns come from MOT defect codes — not manufacturer service bulletins, recalls, or a diagnosis of any individual car. Failures and advisories are listed separately.

Advisories

Notes recorded at the test that appear more often than on similar cars.

Advisory notes recorded on failed first-attempt tests that appear more often than on similar cars.

# Advisory pattern Location Notes vs similar cars Share Confidence
1 Flexible brake hoses (rear)
Brakes > Flexible brake hoses
 Rear 20 ×2.2 6.8% Elevated
Note: Advisories are not a fail rate — they flag issues noted at the test, often before they become failures.

FAQs

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

We do not show a single reliability score for the 2004 Mercedes-Benz Sl on this page. Among 292 failed first-attempt MOT tests (test year 2025), Ball joint dust cover (front) appears more often than on similar cars (about 4.3× more often than similar cars; 28 observed failures; 9.6% of failed tests). Treat this as a pre-purchase checklist from DVSA open data — not a guarantee for any individual car.
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Ball joint dust cover (front) (about 4.3× more often than similar cars; 28 observed failures; 9.6% of failed tests). These are statistical signals, not a diagnosis of any individual car.
Ball joint dust cover (front) shows up more often than on similar cars (about 4.3× more often than similar cars; 28 observed failures; 9.6% of failed tests). That does not prove a design fault — age, mileage, and how the car was used still matter. Treat it as a pre-purchase check point, not a manufacturer service bulletin.
Common MOT problem areas for the 2004 Mercedes-Benz Sl include Ball joint dust cover (front), Rigid brake pipes (front), Coil spring (front). These patterns show up more often than on similar cars after we filter out sparse noise — not a full list of every possible fault on an 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 Mercedes-Benz Sl (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.
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.

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.
  • We never invent pass rates, star scores, or ranks when those data marts are missing.

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

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See brand-wide MOT rankings and year guidance for Mercedes-Benz (separate from this model-year report).