Used car guide

1991 Mercedes-Benz 300: common problems and what to check

What gets flagged at MOT on 1991 Mercedes-Benz 300s, from 337 tests in 2025, plus known faults and what to look at before you buy one.

Small sample: only 337 of these were MOT tested in 2025, so treat the percentages as rough. The known faults below don't depend on it.

337MOT tests in 2025
75%pass first time (all 1991 cars: 71%)
3,600typical miles a year
2.2×the usual rate for track rod ends

What stands out

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

  • Track rod ends2.2× usual
    Mercedes-Benz 300
    8.9% All 1991 cars
    4.1%

    Failed outright at MOT: 3%, against 1.4% of all 1991 cars. The rest were advisories or minor defects.

    Rough price £50–£150 (one end, plus about £30–£50 if it needs a wheel alignment) ClickMechanic

    At the viewing: On a straight road the steering wheel should sit straight. Listen for knocks when turning, and check the steering feels even.

By area

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

  • Suspension
    35% 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
    30% 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
    23% of testsRough price £10–£80

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

  • Oil and fluid leaks
    22% 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.

  • Tyres
    17% 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.

  • Exhaust and emissions
    12% 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.

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Other years

YearMOT testsMost flagged
1993184Suspension 30%
1992362Suspension 30%
1990280Suspension 29%

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