Mercedes 420 Se Auto MOT Pass Rate
Overall pass rate across all manufacture years, based on 35 real MOT test results. Failure rate: 51.4%.
Data from official DVSA MOT testing records
Mercedes 420 Se Auto MOT Reliability Overview
The Mercedes 420 Se Auto is a rare vehicle in the UK, with 35 MOT test results recorded in our database spanning 0 manufacture years. It has an overall MOT pass rate of 48.6% and a failure rate of 51.4%, which is significantly below the UK average of approximately 37%.
Based on this data, the Mercedes 420 Se Auto earns a "Very Poor" reliability rating. The average Mercedes 420 Se Auto presents for MOT with approximately 123,450 miles on the clock.
The most common MOT failure for the Mercedes 420 Se Auto is Lamps, Reflectors and Electrical Equipment, affecting 40.0% of all tests. Lighting failures cover all external lights: headlights, tail lights, brake lights, indicators, fog lights, and reflectors. A single blown bulb will cause an MOT fail. This is one of the most preventable failure categories. The second most common issue is Suspension at 37.1%. Exhaust, Fuel and Emissions rounds out the top three at 22.9%. Together, these top 3 failure categories account for a significant portion of all MOT failures for this model.
Top failures across all manufacture years combined. Individual year pages may show different top failures.
What Fails Most
* High Fail Rate badge indicates an MOT pass rate below 65% (failure rate above 35%).
What Fails on This Car?
Click a category to see specific failure items.
View as table
| Rank | Failure Category | Rate (%) | Count |
|---|---|---|---|
| 1 | Suspension | 62.9% | 22 |
| 2 | Lamps, Reflectors And Electrical Equipment | 57.1% | 20 |
| 3 | Brakes | 40.0% | 14 |
| 4 | Exhaust, Fuel And Emissions | 28.6% | 10 |
| 5 | Steering | 22.9% | 8 |
| 6 | Tyres | 20.0% | 7 |
| 7 | Registration Plates And Vin | 11.4% | 4 |
| 8 | Driver's View Of The Road | 8.6% | 3 |
| 9 | Seat Belts And Supplementary Restraint Systems | 5.7% | 2 |
| 10 | Body, Structure And General Items | 5.7% | 2 |
Failures per 10,000 Miles
avg. 123,450 miFor every 10,000 miles driven, this shows what percentage of MOT tests fail for each category. This accounts for how far cars are actually driven, not just raw pass/fail counts.
View as table
| Category | Rate / 10K mi | Raw % | Count |
|---|---|---|---|
| Suspension | 5.09 | 62.9% | 22 |
| Lamps & Electrical | 4.63 | 57.1% | 20 |
| Brakes | 3.24 | 40.0% | 14 |
| Emissions & Exhaust | 2.31 | 28.6% | 10 |
| Steering | 1.85 | 22.9% | 8 |
| Tyres | 1.62 | 20.0% | 7 |
| Registration Plates and VIN | 0.93 | 11.4% | 4 |
| Visibility | 0.69 | 8.6% | 3 |
| Seat Belts | 0.46 | 5.7% | 2 |
| Body & Structure | 0.46 | 5.7% | 2 |
🚗 Similar Cars to Consider
Mileage at MOT
The average Mercedes 420 Se Auto has 123,450 miles when tested for MOT.
📊 Mileage-Adjusted Failure Rate
How often this car fails MOT relative to how much it's driven — a fairer comparison than raw pass rate.
The Mercedes 420 Se Auto has a mileage-adjusted failure rate of 4.16% per 10,000 miles driven. The average across all makes is 5.38%, so this model is better than average.
About Mercedes 420 Se Auto MOT Data
The Mercedes 420 Se Auto is a rare vehicle in the UK, with 35 MOT test results recorded in our database spanning 0 manufacture years. It has an overall MOT pass rate of 48.6% and a failure rate of 51.4%, which is significantly below the UK average of approximately 37%.
For Mercedes 420 Se Auto owners, these results suggest above-average failure risk — thorough pre-MOT checks are recommended. Focus your pre-MOT checks on lamps, reflectors and electrical equipment and suspension for the best chance of a first-time pass. Use our detailed year-by-year breakdown and failure analysis below to understand how your specific 420 Se Auto is likely to perform.
Lamps, Reflectors and Electrical Equipment — 40.0% of failures
Lamps, Reflectors and Electrical Equipment issues account for 40.0% of MOT failures on the Mercedes 420 Se Auto. Lighting failures cover all external lights: headlights, tail lights, brake lights, indicators, fog lights, and reflectors. A single blown bulb will cause an MOT fail. This is one of the most preventable failure categories. Typical repair costs: £5–50. Pre-MOT check: Walk around the car and check every light — headlights (dipped and main beam), side lights, tail lights, brake lights, indicators, hazard lights, reverse light, rear fog light, and number plate lights. Replace any blown bulbs before the test.
Suspension — 37.1% of failures
Suspension issues account for 37.1% of MOT failures on the Mercedes 420 Se Auto. Suspension failures typically involve worn bushes, leaking shock absorbers, broken coil springs, and damaged suspension arms. These affect ride quality, tyre wear, and road holding. Typical repair costs: £200–500. Pre-MOT check: Look for uneven tyre wear, listen for clunking over bumps, and check if the car pulls to one side. A bouncy ride suggests worn shock absorbers. Visually inspect coil springs for cracks.
Exhaust, Fuel and Emissions — 22.9% of failures
Exhaust, Fuel and Emissions issues account for 22.9% of MOT failures on the Mercedes 420 Se Auto. Emissions failures occur when exhaust gases exceed legal limits for carbon monoxide (CO), hydrocarbons (HC), or particulate matter (diesel). Common causes include faulty oxygen sensors, clogged catalytic converters, or DPF issues on diesel vehicles. Typical repair costs: £100–1,000+. Pre-MOT check: If the engine management light is on, get it diagnosed before the MOT. For diesel cars, ensure the DPF has completed a regeneration cycle. Regular servicing and using premium fuel before the test can help.
Frequently Asked Questions
What is the MOT pass rate for the Mercedes 420 Se Auto?
Based on 35 (based on limited data) MOT tests in our database, the Mercedes 420 Se Auto has an overall pass rate of 48.6% (51.4% fail rate).
What are the most common MOT failures on a Mercedes 420 Se Auto?
The top 3 reasons a Mercedes 420 Se Auto fails its MOT are: 1. Lamps, Reflectors and Electrical Equipment (40.0%), 2. Suspension (37.1%), 3. Exhaust, Fuel and Emissions (22.9%). Check these areas before booking your MOT.
Is the Mercedes 420 Se Auto reliable?
With a 51.4% MOT failure rate, the 420 Se Auto is less reliable than average compared to the UK average of ~40%.
What should I check before an MOT on my Mercedes 420 Se Auto?
Based on failure data, focus on: Lamps, Reflectors and Electrical Equipment (40.0%); Suspension (37.1%); Exhaust, Fuel and Emissions (22.9%). These are the areas most likely to cause a fail. Also check all lights, tyres (minimum 1.6mm tread), and windscreen condition — these are quick wins that apply to all cars.
Based on DVSA anonymised MOT test data (2005–2024). Crown copyright, Open Government Licence v3.0.