If you are considering buying a used Mercedes-Benz M-Class, there are several major reliability issues worth knowing about first. Our garage database tracks 3 known faults for this model, 3 of them rated high severity. Every one below is a repair bill a seller has good reason not to mention.
Found a Mercedes-Benz M-Class for sale?
Paste the advert and we read it against its known faults, its MOT history and the DVLA record, and tell you what the seller has not. Free, about a minute, no card.
Check a Mercedes-Benz M-Class advert (free) →One owner each, in their own words rewritten as a line, and not counted in our risk scoring. A fault joins the list above once a second report or an editorial source backs it.
Sellers rarely admit these faults outright
We track 9 specific phrases sellers use in adverts to soft-pedal these exact issues. Paste any Mercedes-Benz M-Class advert and we check it in seconds.
Check an advert now (free) →An overdue cambelt is the most expensive thing a seller can fail to mention on a used M-Class. These are the figures UK specialists work to.
Generally robust, but can stretch at high mileages. The primary failure point on this engine is the oil cooler seals in the 'V', not the chain.
Officially 'sealed for life' but independent specialists recommend ATF (MB 236.14 spec, which supersedes 236.10 and 236.12) and filter changes every 40,000 miles to head off valve body and conductor plate trouble. Capacity is about 7.5 litres. Fitted to most pre-2011 rear-wheel-drive Mercedes including the pre-2010 C, E and SLK.
Always confirm against the vehicle handbook. Intervals vary by engine, and several manufacturers revised theirs after failures in service.
The Mercedes-Benz M-Class has 3 known faults in our database, 3 of them rated high severity. The most serious are engine (oil cooler seals fail in the 'V' of the engine causing massive oil leaks) and engine (soft metal on the balance shaft timing gear wears completely away). None of them makes the car a bad buy on its own; the risk is a seller who knows and says nothing.
Three stand out. Engine: oil cooler seals fail in the 'V' of the engine causing massive oil leaks (typically 60000 to 100000 miles). Engine: soft metal on the balance shaft timing gear wears completely away, destroying engine timing (typically 60000 to 90000 miles). Suspension: air suspension compressor failure, relay failure, or leaking air struts causing the car to collapse (typically 80000 to 120000 miles). The full list above is grouped by generation, with typical mileage and a rough repair cost for each.
No Mercedes-Benz M-Class year is a write-off, but the W220 / W211 / W164 (1999 to 2011) carries the most serious faults: engine and suspension. Year matters less than whether the specific car has had the known fixes, so check the history for them.
Ask the seller about the engine and suspension faults on this page and whether they have been fixed, with invoices. On the test drive watch for oil pooling in the engine valley, engine Management Light (EML) on and car sitting very low over the wheels. Read the MOT history for repeat advisories, then paste the advert into the free check, which reads it against all 3 known faults before you travel. Check a Mercedes-Benz M-Class advert →
Looking at a Mercedes-Benz M-Class right now? Check the advert before you go and see it.
If you used to check the Honest John “Good & Bad” section before the site closed in 2026, this page is where that information now lives. We rebuilt the Mercedes-Benz M-Class owner-report history from the archived Honest John dataset, added our own research, specialist and owner-club sources and DVSA recall data, and we keep it free. Each fault above is badged with its source. The same data feeds our free advert check, which reads a listing against every known fault for the exact engine and year.
CarAdCheck is not affiliated with Honest John or Volkswagen Financial Services. What happened to Honest John, and where each feature lives now.
Knowing what a Mercedes-Benz M-Class goes wrong with is half of it. The rest is reading the advert and checking the car's history before you hand any money over.