Used car guide

1991 Mercedes-Benz 300 diesel: common problems and MOT failures

What MOT testers find on the diesel Mercedes-Benz 300 first registered in 1991 (diesel cars only): we looked at the 241 MOTs these cars had during 2023–2025. Plus known faults and what to look at before you buy one.

Small sample: there were only 241 MOTs of these cars during 2023–2025, so treat the percentages as rough. The known faults below don't depend on it.

241MOTs of 1991 diesel cars, done in 2023–2025
65%pass first time (all 1991 cars: 71%)
5,200typical miles a year
2.5×the usual rate for rigid brake pipes

What goes wrong more than usual on a 1991 Mercedes-Benz 300 diesel?

Parts flagged at MOT more often on the 1991 Mercedes-Benz 300 diesel than on all cars registered in 1991.

  • Rigid brake pipes2.5× usual
    Mercedes-Benz 300
    29.5% All 1991 cars
    11.6%

    Failed outright at MOT: 4.1%, against 1.6% of all 1991 cars. The rest were advisories or minor defects.

    Rough price £100–£400 our estimate

    At the viewing: Ask to see underneath, or check the MOT advisories: corroded brake or fuel pipes get worse every year and fail the MOT when they do.

  • Tread depth2.3× usual
    Mercedes-Benz 300
    13.3% All 1991 cars
    5.8%

    Failed outright at MOT: 0.4%, against 0.6% of all 1991 cars. The rest were advisories or minor defects.

    Rough price £70–£150 our estimate

    At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.

Common 1991 Mercedes-Benz 300 diesel MOT failures and advisories

The share of 1991 Mercedes-Benz 300 diesel MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Suspension
    46% of testsRough price £120–£400

    At the viewing: Listen for knocks over speed bumps, and look behind each front wheel for a snapped coil spring.

  • Brakes
    46% of testsRough price £150–£350

    At the viewing: Look for a lip on the disc edges and feel for judder or pulling when braking firmly from about 40mph.

  • Lights and electrics
    32% of testsRough price £10–£80

    At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.

  • Tyres
    22% of testsRough price £70–£150

    At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.

  • Oil and fluid leaks
    21% of testsRough price £80–£600

    At the viewing: Look under the engine and on the ground where the car is usually parked for fresh oil or fluid.

  • Exhaust and emissions
    18% of testsRough price £100–£1,200

    At the viewing: Look for black soot in the tailpipe, listen for blowing from the exhaust and check for engine or DPF warning lights.

Questions to ask the seller before buying a 1991 Mercedes-Benz 300 diesel

Ask before you travel to see it. A seller who knows the car will have answers, and receipts.

  1. Any recent work on the rigid brake pipes? (Flagged at MOT 2.5× as often on the 1991 Mercedes-Benz 300 diesel as on other cars the same age.)
  2. Any recent work on the tread depth? (Flagged at MOT 2.3× as often on the 1991 Mercedes-Benz 300 diesel as on other cars the same age.)
  3. 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, mileage and what to ask the seller. Free, no sign-up.

Other years

Every year of the Mercedes-Benz 300 compared

YearMOT testsMost flagged
2005–Too few tests
2004–Too few tests
2003–Too few tests
2002–Too few tests
2001–Too few tests
2000–Too few tests
1999–Too few tests
1996–Too few tests
1995–Too few tests
1994–Too few tests
1993609Suspension 30%
19921,161Suspension 31%
1990881Suspension 30%
1989–Too few tests
1988–Too few tests
1987–Too few tests
1986–Too few tests
1985–Too few tests
1984–Too few tests
1983–Too few tests
1982–Too few tests
1981–Too few tests
1980–Too few tests
1979–Too few tests
1978–Too few tests
1977–Too few tests
1976–Too few tests
1975–Too few tests
1974–Too few tests
1973–Too few tests
1972–Too few tests
1971–Too few tests
1965–Too few tests
1955–Too few tests

Where this comes from: the DVSA's anonymised results for every MOT test done in Great Britain during 2023–2025, counting the MOTs of Mercedes-Benz 300 cars first registered in 1991. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score