Mercedes-Benz 300 common problems and MOT failures
What goes wrong on a used Mercedes-Benz 300, year by year: known faults from UK buying guides, the parts flagged at MOT more than on other cars (from 3,752 MOTs done during 2023–2025), and what to check before you buy one.
The 1979 Mercedes-Benz 300
Our MOT figures start with cars first registered in 1990. There are no known faults on record for this year in the UK buying guides we use, so the rest of this page covers the Mercedes-Benz 300 as a whole.
What to check on a 1979 car
- Rust and structure
Look underneath at the sills, floor, chassis rails and jacking points. Rust in the structure costs far more to fix than paint bubbles.
- MOT-exempt isn’t roadworthy
Cars over 40 don’t need an MOT, but they must still be safe. A voluntary MOT or a specialist inspection is worth the money.
- Paperwork
Old MOT certificates, bills and restoration photos show how it has been looked after. Check the logbook matches the car’s VIN and engine number.
- Originality
Changes from standard affect value and insurance. Ask what has been replaced or modified.
- Insurance
Classic insurance is often cheaper but may limit mileage and use. Get a quote before you buy.
Other years
Most years have their own guide. The year is when the car was first registered (it’s on the logbook, or check the reg below).
20052004200320022001200019991996199519941993199219911990198919881987198619851984198319821981198019791978197719761975197419731972197119651955
What usually goes wrong with a Mercedes-Benz 300?
We haven’t found widely reported faults for the Mercedes-Benz 300 in the UK buying guides we use yet. That doesn’t mean it has none, so check the car carefully and look at the MOT weak spots below.
Common Mercedes-Benz 300 MOT failures to check
Parts flagged at MOT well above the usual rate for cars the same age, for each fuel on its own. From the DVSA’s results for every MOT done in Great Britain during 2023–2025.
Petrol
Ball joint dust cover
up to 2.3× usualStands out on cars registered in 1990, 1991 and 1992.
Rough price £60–£150 (one joint) ClickMechanicAt the viewing: Listen for knocking over bumps and check the rubber boots behind the wheels aren't split.
Coil springs
up to 2.1× usualStands out on cars registered in 1990, 1991 and 1992.
Rough price £175–£400 (pair, one axle) ClickMechanicAt the viewing: Look behind each wheel for a snapped spring coil, and listen for a clunk or twang when turning the wheel lock to lock with the car stopped.
Mercedes-Benz 300 MOT pass rate by year
Older cars fail more, so compare each year with all cars registered the same year.
Questions to ask the seller before buying a Mercedes-Benz 300
Ask before you travel to see it. A seller who knows the car will have answers, and receipts.
- Any recent work on the coil springs? (Flagged at MOT 2.1× as often on the Mercedes-Benz 300 as on other cars the same age.)
- Any recent work on the corroded fuel pipes? (Flagged at MOT 2.6× as often on the Mercedes-Benz 300 as on other cars the same age.)
- Can I see the service history and receipts for any big jobs?
Looking at a Mercedes-Benz 300?
Check the actual car: its own MOT history, whether it already shows these weak spots and what to ask the seller. Free, no sign-up.
Where this comes from: MOT figures are the DVSA’s anonymised results for every MOT test done in Great Britain during 2023–2025, grouped by the year each car was first registered. How many are on the road is from the Department for Transport’s vehicle licensing statistics. Known faults are from UK buying guides, in our own words, with links. How we score