Mercedes-Benz 420: MOT pass rate and reliability data

The Mercedes-Benz 420 passes its MOT first time more often than the average UK car, by 4.1 percentage points. These figures come from the DVSA's full year of anonymised MOT results, covering 594 individual Mercedes-Benz 420 tests. Nothing here is an estimate or a survey.

The numbers

First-time pass rate80.8%
UK national average76.7%
Difference+4.1 points
Tests analysed594
Average mileage at test100,326 miles
Average year of manufacture1988
Reliability rank1,414 of 2,005 models

What this means if you are buying one

A 80.8% first-time pass rate means roughly 19 in every 100 Mercedes-Benz 420s presented for MOT fail on the first attempt. That is better than average, so a well-kept example is a reasonably safe used buy. The average Mercedes-Benz 420 tested had covered 100,326 miles and was built around 1988.

What this means at salvage auction

Pass rate is a proxy for what a car costs to keep on the road. The Mercedes-Benz 420 sits 4.1 points above the national average, ranked 1,414 of 2,005 models. On one bought as repairable salvage, the mechanical side is less likely to spring surprises, so your repair estimate should hold up reasonably well.

Before you bid: run the lot through the analyzer, check the car's own record, check the mileage, decode the VIN, and if it carries a marker use the write-off value calculator. Or compare it against another model.

Looking at a specific Mercedes-Benz 420 rather than the model in general? The free check covers its MOT and mileage history, and the full HPI report confirms the insurance write-off category, outstanding finance and whether it is recorded stolen, from licensed data for 5 credits. Already own one that has been damaged? Work out whether fixing it beats selling it with the repair or scrap calculator, and see recorded closing bids for damaged Mercedes-Benz 420s at UK salvage auction.

Most common MOT failures on a Mercedes-Benz 420

  1. A suspension joint dust cover missing or no longer prevents the ingress of dirt etc, 5.9% of tests (3.21x the national rate for this defect)
  2. Significant brake effort recorded with no brake applied indicating a binding brake, 2.9% of tests (2.76x the national rate for this defect)
  3. 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, 2.5% of tests (2.68x the national rate for this defect)
  4. A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED, 2.5% of tests (2.06x the national rate for this defect)
  5. The aim of a headlamp is not within limits laid down in the requirements, 4.7% of tests (2.01x the national rate for this defect)
  6. Windscreen washers not working or not providing sufficient fluid to clear the windscreen, 2.7% of tests (1.6x the national rate for this defect)
  7. Exhaust system leaking or insecure, 2.2% of tests (2.17x the national rate for this defect)
  8. Wiper blade missing or obviously not clearing the windscreen, 2% of tests
  9. 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, 1.7% of tests (3.83x the national rate for this defect)
  10. Emissions levels exceed default limits, 1.7% of tests (4.77x the national rate for this defect)

From 593 DVSA-tracked Mercedes-Benz 420 tests, 2024. DVSA testers marked 2.86% of these flagged Mercedes-Benz 420 defects as "dangerous", meaning the tester judged the car unsafe to drive away, against 5.11% nationally.

Most common MOT advisories on a Mercedes-Benz 420

An advisory doesn't fail the car - the tester flags it as worth watching, but it still passes. A different list from the failures above: what testers are noting on a Mercedes-Benz 420 before it actually fails on it.

  1. A wheel bearing with excessive play, 2.9% of tests (4.42x the national rate for this advisory)
  2. Significant brake effort recorded with no brake applied indicating a binding brake, 6.2% of tests (3.12x the national rate for this advisory), also fails
  3. Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users, 17.2% of tests (3.09x the national rate for this advisory)
  4. 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, 4.4% of tests (2.89x the national rate for this advisory), also fails
  5. Exhaust system leaking or insecure, 7.1% of tests (2.49x the national rate for this advisory), also fails
  6. A brake hose ferrule excessively corroded, 2.9% of tests (2.25x the national rate for this advisory)
  7. Brake pipe damaged or excessively corroded, 11.5% of tests (1.85x the national rate for this advisory)
  8. A spring or spring component fractured or seriously weakened, 6.7% of tests (1.43x the national rate for this advisory)
  9. A tyre seriously damaged, 9.4% of tests
  10. A suspension pin, bush or joint excessively worn, 6.9% of tests

From 593 DVSA-tracked Mercedes-Benz 420 tests, 2024.

Other Mercedes-Benz models

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Mercedes-Benz 420 MOT pass rate badge: 80.8%

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Mercedes-Benz 420 most common MOT failure: A suspension joint dust cover missing or no longer prevents the ingress of dirt etc (5.9% of tests)

<a href="https://www.salvageprophet.co.uk/mot/mercedes-benz-420"><img src="https://www.salvageprophet.co.uk/badge/failure/mercedes-benz-420.svg" width="340" height="106" alt="Mercedes-Benz 420 most common MOT failure: A suspension joint dust cover missing or no longer prevents the ingress of dirt etc (5.9% of tests) - Salvage Prophet"></a>

All 2,005 models ranked by MOT pass rate