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What to check: Mercedes B-Class

CBy age

BBy miles

Ranked across all years of the Mercedes B-Class, from its own MOT record and from what owners report. Tick it off at the car.

From this model's MOT record

The physical checks its own defect data says are worth your time, most telling first.

Lights and horn walkroundRuns high on this modelWith a helper, run every light: dipped, main beam, indicators, brake lights including the high-level one, reverse, fog, and the horn. On newer cars a dead LED section can mean replacing the whole lamp unit rather than a bulb.Recorded on 3.2% of tests at age 6-9 · class average 0.6%

Coil springsRuns high on this modelLook through the wheel spokes at the bottom coil of each spring; when springs snap it is usually there, and the break is visible. Step back and check the car sits level too. A dropped corner is often a broken spring.Recorded on 2.6% of tests at age 6-9 · class average 1.4%

Rubber boots and gaitersRuns high on this modelOn full steering lock, look in behind each front wheel at the concertina rubber boots on the driveshafts and steering rack. Splits, or grease flung around the arch, mean dirt is getting into a joint that costs far more than the boot protecting it.Recorded on 2.1% of tests at age 6-9 · class average 1.0%

Bushes and ball jointsRuns high on this modelDrive slowly over broken tarmac with the windows down and listen for clonks from either end. Back at the car, have someone rock the steering wheel while you rest a hand on each front wheel; play you can feel through the tyre is a worn joint.Recorded on 1.9% of tests at age 6-9 · class average 0.9%

WheelsRuns high on this modelLook at each rim for kerb damage and check no wheel nuts are missing. A steering wheel that shimmies between 50 and 60 on the test drive often turns out to be a buckled or badly balanced wheel.Recorded on 1.3% of tests at age 6-9 · class average 0.6%

Brake pipes underneathFollow the metal brake lines with a torch where they run along the sills and over the rear axle. White crust or flaking metal means they are corroding, and the online MOT history usually shows the same advisory creeping up for years before the fail.Recorded on 1.7% of tests at age 6-9 · class average 1.9%

Warning lights on ignitionTurn the ignition on without starting the engine and watch the dash. Every warning light should appear, then go out once it is running. Be more suspicious of a light that never comes on at all than of one that stays on; warning bulbs have been known to vanish before a sale.Recorded on 1.0% of tests at age 6-9 · class average 0.4%

Worth doing on any used car

These judge the seller's upkeep rather than the model.

Tyres, all fourCheck the tread across the full width of each tyre, inner edge included, and look for cracking and mismatched brands. A set of decent tyres is £500 or more on most cars, which makes this the easiest money to take off a price. If the pressure warning light is on, budget for sensors too.Recorded on 18.8% of tests at age 6-9 · class average 20.1%

Pads and discsLook through the wheel spokes at the brake disc. A pronounced lip on its outer edge, or a rusty and scored face, means discs and pads are due all round, a few hundred pounds on most cars. A haggling point rather than a reason to walk away.Recorded on 9.8% of tests at age 6-9 · class average 8.7%

Windscreen and wipersScan the glass in daylight for chips, especially in the driver's line of sight where even a small one can fail the MOT. Run the washers and check the wipers clear without smearing.Recorded on 2.1% of tests at age 6-9 · class average 2.0%

Because of what owners report

Drawn from the owner reports rather than the MOT data. These are the model-specific ones.

Pull away gently from cold in Drive and again from a stop at low speed.Hesitation, lurching or a sudden surge points to the 7G-DCT gearbox issue.

Ask for the service history and check for a transmission oil/filter change around 3 years or 38,000 miles.No record of it raises the risk of DCT clutch wear later.

On a 2005-2011 automatic, watch for harsh, delayed or slipping shifts.Early signs of the Autotronic CVT gearbox wearing out, an expensive fix.

Turn the car off and restart it cold a couple of times.Any failure or hesitation to start on a 2011-plate car suggests the EIS module fault.

Lift the bonnet and boot floor and check the battery box and spare wheel well for damp or rust staining.Signs the bulkhead vent drains have been blocking and letting water in.

On a diesel, ask whether it's mostly done short trips, and listen for rough cold starts or a warning light.Glow plug corrosion is more likely on cars that rarely get up to full temperature.

On a B250e electric, check the 12V battery health and ask about any 'visit workshop' warnings.A history of these points to the battery drain problem specific to the electric version.

Full Mercedes B-Class reliability report