Model Reports 5 min read Updated 18 Oct 2026

Mercedes-Benz SLC 2017: reliability & common MOT faults

In 2025, 82 in every 100 first MOTs on a 2017 Mercedes-Benz SLC were passes. Most common reason for a fail: Tyre condition (front).

Summary

At the same mileage, a petrol 2017 Mercedes-Benz SLC passed first time more often than a diesel one: 84 in every 100 against 79 in every 100.

At a glance

How 3,309 first tests went in 2025.

Passed first time
82 in every 100
Did not pass first time
18 in every 100585 failed first-attempt tests
The typical car
8 yearsabout 36,271 miles
First tests counted
3,309

What failed most often

  1. Tyre condition (front)20 in every 100 failed tests
  2. Suspension arm ball joint (front)16 in every 100 failed tests
  3. Coil spring (rear)9 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 2017 Mercedes-Benz SLC vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. A wear pattern follows age and use more than the way the car was built. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.

Brakes

One fault: anti-lock braking system (ABS), 6.8 times as often as on similar cars.

Figures below are measured across the 585 failed first attempts in 2025 that had a mileage recorded, which allows a like-for-like comparison.

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.

Anti-lock braking system (ABS)

Failed on 30 first tests6.8 times as often as similar carsLikely evidence

What it means

ABS is failed as removed only where it has obviously been removed, because not every vehicle in the age range where removal is not permitted has ABS. A warning lamp that does not light or shows an ABS fault is Major, as is a missing or excessively damaged wheel speed sensor. Every failure row for this component is Major.

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

Suspension

Four faults. The strongest is the suspension arm ball joint (front): 6.3 times as often as on similar cars.

Suspension arm ball joint (front)

Failed on 95 first tests6.3 times as often as similar carsLikely evidence

What it means

A suspension arm ball joint is failed under the general suspension pin, bush or joint wording. Excessively worn is Major, and likely to become detached is graded Dangerous.

Anti-roll bar linkage ball joint dust cover (front)

Failed on 26 first tests5.0 times as often as similar carsPossible evidence

What it means

A suspension joint dust cover that is severely deteriorated is Minor. It becomes Major once it is missing or no longer prevents the ingress of dirt, so what matters is whether it still keeps dirt out. DVSA words this for any suspension joint dust cover, and files it here under anti-roll bars.

Suspension arm ball joint dust cover (front)

Failed on 34 first tests3.5 times as often as similar carsLikely evidence

What it means

Whether a suspension arm ball joint dust cover still keeps dirt out decides its grade. Severely deteriorated is Minor, while missing, or no longer preventing the ingress of dirt, is Major.

Coil spring (rear)

Failed on 52 first tests2.1 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.

Tyres

One wear pattern: tyre tread depth (rear), 2.4 times as often as on similar cars.

Tyre tread depth (rear)

Failed on 30 first tests2.4 times as often as similar carsWear pattern

What it means

Only primary grooves count when tread depth is assessed: those holding the wear indicators, or cut as deep as those when new. Shallower secondary grooves are ignored. Tread depth below the minimum for the vehicle is Dangerous, and so is a pattern not visible over the whole tread, but that second row applies only to vehicles that need the lower minimum.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 83 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.

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.

Wheel bearings (front)

Noted on 22 first tests21 times as often as similar carsElevated evidence

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
82in every 100
Passed on the first test.
Fixed at the station
2in every 100
Failed, then fixed at the test station the same day.
Failed
16in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 82.3% of 3,309 first tests (2025): only cars that passed first time count. Official-style pass 84.0%: cars fixed at the test station also count as a pass. The 2 fixed and the 16 not fixed make the 18 in every 100 that did not pass first time.

Petrol and diesel

First testsTypical mileagePassed first time, as testedPassed first time, same mileage
Petrol1,84232,848 miles8684
Diesel1,46741,335 miles7879

Figures are in every 100 first tests. Cars with more miles usually fail more often, so the same-mileage figure gives every fuel the mileage mix of all the cars in this year.

Same model, other years

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

40608010020162017201820192020Older carsNewer cars
40608010020162017201820192020Newer 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, 84 in every 100 passed first time.

YearPassed first timeFirst tests
201684 in every 1002,186
2017 This car82 in every 1003,309
201889 in every 1001,441
201988 in every 100957
202089 in every 100574

If you are buying one

What this year's MOT record means for the decision in front of you.

Mileage matters most on a 2017 Mercedes-Benz SLC.

Of 2017 Mercedes-Benz SLC vehicles with under 23,000 miles, 91 in every 100 passed their 2025 MOT first time. With 53,000 miles or more, 73 in every 100 did.

Under 23,000664 tests
91
23,000–32,000657 tests
86
32,000–41,000 Typical car680 tests
84
41,000–53,000633 tests
78
53,000 and over675 tests
73

Petrol or diesel?

Typical mileagePassed first time,
as tested		Passed first time,
same mileage
Petrol32,848 miles8684
Diesel41,335 miles7879

Figures are in every 100 first tests. Part of the gap is mileage: diesel cars have done more miles. Even at the same mileage, petrol passed more often (84 against 79 in every 100).

What to check at your mileage

How often each fault turned up on a failed first test, by the car's mileage. Read it as: what is likely to need looking at on a car like the one in front of you.

Under 23,00032,000–41,00053,000 and over
Tyre condition (front)2.32.55.8
Suspension arm ball joint (front)0.82.26.1
Coil spring (rear)0.81.52.5

Faults per 100 first tests, by the car's mileage at the test.

When a car fails

54in every 100

of failed cars had one item to fix.

15in every 100

of failed cars had three or more items to fix.

5in every 100

of all first tests had a defect the tester marked dangerous (unsafe to drive away).

Every figure here is a first-attempt MOT rate from DVSA open data for this model line, for cars of this model year tested in 2025. Each mileage band holds a fifth of the tests. MOTs do not test engine or gearbox internals, so this is a pre-purchase checklist, not a full reliability score.

FAQs

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

At the same mileage, a petrol 2017 Mercedes-Benz SLC passed first time more often than a diesel one: 84 in every 100 against 79 in every 100. In 2025, 82.3% of 3,309 first MOTs on the 2017 Mercedes-Benz SLC passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 84.0%. Among 585 failed first-attempt MOT tests (test year 2025), Anti-lock braking system (ABS) appears more often than on similar cars (5.1% of those tests; 30 observed failures; about 6.8× 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 2017 Mercedes-Benz SLC at the first attempt were Tyre condition (front) (20.0%), Suspension arm ball joint (front) (16.2%) and Coil spring (rear) (8.9%), 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: Anti-lock braking system (ABS) (5.1% of those tests; 30 observed failures; about 6.8× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Anti-lock braking system (ABS) shows up more often than on similar cars (5.1% of those tests; 30 observed failures; about 6.8× 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 2017 Mercedes-Benz SLC include Anti-lock braking system (ABS), Suspension arm ball joint (front), Anti-roll bar linkage ball joint dust cover (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 2017 Mercedes-Benz SLC (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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