Mercedes-Benz 420
From 1,429 MOT tests. Above average for its class.
Common MOT failure categories
Pass rate by registration year
What goes wrong?
The most common MOT failure reasons are the aim of a headlamp is not within limits laid down in the requirements, a suspension joint dust cover missing or no longer prevents the ingress of dirt etc and a suspension joint dust cover severely deteriorated. The top issue, the aim of a headlamp is not within limits laid down in the requirements, caused 42 failures in 2024. If you need repairs before retesting, sites like BookMyGarage let you compare local prices.
| the aim of a headlamp is not within limits laid down in the requirements | 42 |
| a suspension joint dust cover missing or no longer prevents the ingress of dirt etc | 41 |
| a suspension joint dust cover severely deteriorated | 26 |
| wiper blade missing or obviously not clearing the windscreen | 24 |
| a headlamp or light source missing, inoperative or more than ½ not functioning in the case of led | 24 |
| significant brake effort recorded with no brake applied indicating a binding brake | 19 |
| the strength or continuity of the load bearing structure within 30cm of any sub-frame, spring or suspension component mounting (a 'prescribed area') is significantly reduced or inadequately repaired | 18 |
| vehicle structure corroded to the extent that the rigidity of the assembly is seriously reduced | 18 |
| exhaust system leaking or insecure | 16 |
| a lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning | 15 |
How serious are these failures?
Not all MOT failures are equal. 21.4% of 420 failures could actually strand you: fractured springs, engine faults, exhaust problems. Another 7.8% are safety issues where the car still drives but shouldn't, such as worn brakes, corroded brake pipes, and steering wear. When it does fail, the average repair bill is around £96.
By registration year
| Year | Pass rate | Top failures |
|---|---|---|
| 1989 | 88.2% | an obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning, the strength or continuity of the load bearing structure within 30cm of any sub-frame, spring or suspension component mounting (a 'prescribed area') is significantly reduced or inadequately repaired |
| 1988 | 86.5% | the aim of a headlamp is not within limits laid down in the requirements, a suspension joint dust cover missing or no longer prevents the ingress of dirt etc |
| 1987 | 86.4% | a suspension joint dust cover missing or no longer prevents the ingress of dirt etc, a suspension joint dust cover severely deteriorated |
| 1986 | 83% | the aim of a headlamp is not within limits laid down in the requirements, vehicle structure corroded to the extent that the rigidity of the assembly is seriously reduced |
Typical mileage
Half of all 420s tested had between 70,168 and 127,790 miles on the clock. A significant number are high-mileage vehicles.
At 97,384 median miles, the 420 has 0.015 failures per 10,000 miles driven.
Other Mercedes-Benz models
Common questions
What is the Mercedes-Benz 420 MOT pass rate?
The Mercedes-Benz 420 has a 85.5% MOT pass rate based on 1,429 real MOT tests. This is above the national average.
What are common MOT failures on a Mercedes-Benz 420?
The most common MOT failure on the Mercedes-Benz 420 is the aim of a headlamp is not within limits laid down in the requirements, which caused 42 failures. Other common issues include a suspension joint dust cover missing or no longer prevents the ingress of dirt etc.
What is the typical mileage of a Mercedes-Benz 420 at MOT?
The median mileage at MOT for a Mercedes-Benz 420 is 97,384 miles. The middle 50% of vehicles tested have between 70,168 and 127,790 miles.
Buying a used 420?
Start with the free tools. Look up the specific vehicle's MOT history on GOV.UK The mileage at each test will show if it's been wound back, and the advisory history tells you what's wearing. Cross-reference that against the typical failures above to see if anything looks unusual for this model.
The free data won't tell you about outstanding finance, theft markers, or write-off history. For that, you need a vehicle history check This is especially important on a private sale where you have fewer legal protections.
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MOT data from DVSA anonymised test results, 2024 test year. Fleet data from DfT vehicle licensing statistics. Crown copyright, OGL v3.0. MOT pass rates are statistical summaries of test outcomes, not assessments of individual vehicle safety or condition. Always inspect a vehicle and check its full MOT history before purchasing. See terms of use.