Ford Sierra MOT Failures

An analysis of 11,369 real DVSA MOT tests on the Ford Sierra — what fails, how often, and how that compares to every other car on UK roads. Generations covered: MK1 (1982–1987), MK2 (1987–1993).

Where the Ford Sierra fails its MOT

The single biggest MOT failure point on the Ford Sierra is emissions failure — this model is 315 times more likely to fail on this item than the average car on UK roads. That makes it an extreme outlier for anyone buying or owning this model. Across 11,369 MOT tests, 3.16% of all Ford Sierra tests recorded this as a failure.

Exhaust and emissions failures often point to catalytic converter degradation, lambda sensor faults, or — in diesel models — DPF problems. These can be expensive to fix and will cause an immediate MOT failure.

Other notable weak points include structural corrosion (244x the fleet average), seat mounting fault (184x the fleet average), brake hoses perished or damaged (109x the fleet average), and abs fault (18x the fleet average). These ratios compare the Ford Sierra'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 5 categories: Exhaust & Emissions, Bodywork, Seatbelts & Airbags, Brakes, Suspension. If you're inspecting a Ford Sierra 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 Ford Sierra'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 Ford Sierra specifically, the DVSA data shows the most common failures at this mileage are emissions failure (121x the average) and brake hoses perished or damaged (109x). seat mounting fault (72x) and suspension component damaged or corroded (56x) 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 Ford Sierra specifically, the DVSA data shows the most common failures at this mileage are emissions failure (180x the average) and headlight fault (43x). seat mounting fault (23x) and brake hoses perished or damaged (22x) 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 Ford Sierra specialists and owners flag most frequently, drawn from manufacturer technical bulletins, workshop data, and verified owner reports.

Subframe mounting point corrosion (MK1/MK2) Dangerous

The rear subframe mounting points on the Sierra are prone to severe corrosion that compromises structural integrity. Affects MK1, MK2; typical independent garage repair cost is £800–£1,500.

Brake line corrosion (MK1/MK2) Dangerous

Sierra brake lines are extremely vulnerable to corrosion due to poor routing and inadequate protection. Affects MK1, MK2; typical independent garage repair cost is £400–£800.

Brake hose deterioration (MK1/MK2) Major

Flexible brake hoses on the Sierra are particularly prone to deterioration due to their age and exposure to road conditions. Affects MK1, MK2; typical independent garage repair cost is £150–£300.

Exhaust emissions failure (MK1/MK2) Major

Sierra models show extremely high emissions failure rates, with MOT data indicating failures at This primarily affects the CVH and DOHC engines due to worn carburettor components, degraded ignition timing, and carbon buildup. Affects MK1, MK2; typical independent garage repair cost is £200–£600.

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

What to check before buying a Ford Sierra

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

Exhaust & Emissions — check for emissions failure. Bodywork — check for structural corrosion, vehicle structure corroded to the extent that t..., transmission shaft constant velocity joint boot.... Seatbelts & Airbags — check for seat mounting fault. Brakes — check for brake hoses perished or damaged.

Beyond the MOT items, ask specifically about subframe mounting point corrosion and brake line corrosion. These won't show up on a standard MOT but can be expensive to fix — repairs start from £800. 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.