Mercedes Benz Cla MOT Failures

An analysis of 363,463 real DVSA MOT tests on the Mercedes Benz Cla — what fails, how often, and how that compares to every other car on UK roads. Generations covered: C117 (2013–2019), C118 (2019–2024).

Where the Mercedes Benz Cla fails its MOT

The single biggest MOT failure point on the Mercedes Benz Cla is any fracture or welding defect on a wheel — this model is 39 times more likely to fail on this item than the average car on UK roads. That makes it a significant weak point for anyone buying or owning this model. Across 363,463 MOT tests, 0.42% of all Mercedes Benz Cla tests recorded this as a failure.

Wheel-related failures include cracked alloys, damaged wheel studs, and bearing play. Listen for rumbling at speed (wheel bearings) and check for any visible cracks around alloy spokes.

Other notable weak points include light unit fault (11x the fleet average), window tint too dark (14x the fleet average), anti-roll bar links worn (8.5x the fleet average), and headlight fault (8.4x the fleet average). These ratios compare the Mercedes Benz Cla's failure rate on each item against the national average for all cars tested — a ratio of 10x means this model fails ten times more often than a typical car.

The failures span 6 categories: Wheels, Lights & Electrics, Wipers & Windscreen, Suspension, Tyres and others. If you're inspecting a Mercedes Benz Cla before purchase, these are the areas to focus on — and if any have been flagged as advisories on a previous MOT, they're likely to become failures in the near future.

How failures change with mileage

The Mercedes Benz Cla's weak points shift as the car covers more miles. Understanding these patterns helps you know what to expect — and what to budget for — at each stage of ownership.

Under 60,000 miles

At this mileage, most failures are either design-related or caused by age rather than wear. Components like bushes and drop links may not have been replaced yet, and original-fit parts can deteriorate even on low-mileage cars that spend a lot of time sitting.

For the Mercedes Benz Cla specifically, the DVSA data shows the most common failures at this mileage are any fracture or welding defect on a wheel (39x the average) and wheel with a loose or missing wheel nut, bolt o... (22x). brake lining or pad worn down to wear indicator (12x) and brake fluid significantly below minimum mark (12x) also appear frequently.

60,000 to 100,000 miles

This is where routine wear items start to show up. Brake components, tyres, and exhaust parts have done serious work by this point. Cars that have been well serviced will show fewer of these failures — this mileage band is where good maintenance really separates the well-kept from the neglected.

For the Mercedes Benz Cla specifically, the DVSA data shows the most common failures at this mileage are any fracture or welding defect on a wheel (24x the average) and window tint too dark (12x). light unit fault (7.1x) and headlight fault (6.7x) also appear frequently.

Over 100,000 miles

High-mileage cars accumulate failures across multiple systems. The key question isn't whether things will need doing — they will — but whether the car has been maintained well enough to keep on top of them. Look for a consistent service history and recent MOT passes with minimal advisories.

For the Mercedes Benz Cla specifically, the DVSA data shows the most common failures at this mileage are any fracture or welding defect on a wheel (17x the average) and tyre wear or damage (9.2x). light unit fault (7.1x) and anti-roll bar links worn (5.7x) also appear frequently.

Known issues beyond the MOT

An MOT only tests roadworthiness at a single point in time — it won't catch developing faults, intermittent problems, or issues that haven't yet reached the failure threshold. These are the issues that Mercedes Benz Cla specialists and owners flag most frequently, drawn from manufacturer technical bulletins, workshop data, and verified owner reports.

Excessive brake pad wear (C117/C118) Major

MOT data shows CLA models fail brake pad thickness tests at up to 15.3 times the national fleet average, particularly on 1.6-litre petrol variants at low mileage. Affects C117, C118; typical independent garage repair cost is £150–£400.

Brake fluid loss (C117/C118) Major

MOT data shows CLA models fail brake fluid level tests at up to 11.5 times the national fleet average, particularly affecting 1.3-litre petrol variants in the 40,000-60,000 mile range. Affects C117, C118; typical independent garage repair cost is £200–£500.

Suspension joint dust cover deterioration (C117/C118)

MOT data shows CLA models fail suspension dust cover tests at up to 7.2 times the national fleet average, particularly affecting 2.1-litre diesel variants from 20,000 miles onwards. Affects C117, C118; typical independent garage repair cost is £150–£300.

Engine management light illumination (C117/C118)

The pattern affects all mileage bands including new cars, suggesting emissions system faults rather than wear-related issues. Affects C117, C118; typical independent garage repair cost is £80–£1,500.

For the complete picture — including repair costs across independent, specialist, and dealer garages — see the full Mercedes Benz Cla common problems breakdown.

What to check before buying a Mercedes Benz Cla

Based on the MOT failure data and known issues above, here's what to prioritise when inspecting a Mercedes Benz Cla:

Wheels — check for any fracture or welding defect on a wheel, wheel with a loose or missing wheel nut, bolt o.... Lights & Electrics — check for light unit fault, headlight fault. Wipers & Windscreen — check for window tint too dark. Suspension — check for anti-roll bar links worn.

Beyond the MOT items, ask specifically about excessive brake pad wear and brake fluid loss. These won't show up on a standard MOT but can be expensive to fix — repairs start from £150. A specialist pre-purchase inspection is worth the investment on this model.

Always check the car's full MOT history for patterns — recurring advisories often become failures within 12 months. And verify the service history to confirm maintenance has been kept up to schedule. Enter any reg into our free car check to see the complete picture.

MOT failure data sourced from DVSA bulk test records via data.gov.uk. Ratios compare this model's failure rate against the national fleet average. Known issues sourced from manufacturer bulletins, specialist workshops, and verified owner reports.