The practical Mercedes that seats five in comfort
A tall-bodied hatchback offering S-Class levels of rear legroom in a compact footprint. Not exciting to drive, but the B-Class delivers premium interior quality, strong safety credentials and easy urban manoeuvrability at affordable used prices.
We track 5 known issues across the Mercedes-Benz B Class range, including 2 rated as safety-critical. Knowing which variants and configurations to approach with caution can save you from expensive surprises after purchase.
Found a Mercedes-Benz B Class? Enter the reg to see which of our 5 known issues apply to that exact car, plus full MOT history and mileage checks.
W245 (2005–2011) — Petrol options included the B150, B170, B200, with B200 CDI on the diesel side. Our database flags 5 known issues on this generation, 2 of which are rated as safety-critical. The most significant concern is Brake hose deterioration (£80–£150 to address).
W246 (2011–2018) — Petrol options included the B160, with B180d, B200d on the diesel side. Our database flags 5 known issues on this generation, 2 of which are rated as safety-critical. The most significant concern is Brake hose deterioration (£80–£150 to address).
Flexible brake hoses on B Class models show excessive deterioration, cracking, and stretching at rates far above the fleet average. The hoses connect rigid brake pipes to the brake calipers and must flex with suspension movement. When they fail, brake fluid leaks out and braking performance is severely compromised. This affects all engine variants across all mileage bands including very low-mileage examples, suggesting a material or design issue with the hose specification.
Brake hose failure leads to brake fluid loss and can result in complete brake failure on the affected circuit. The car becomes dangerous to drive and stopping distances increase dramatically. Emergency repair is required immediately and the vehicle should not be driven until repaired.
Check brake disc condition for lipping or scoring. Test braking at moderate speed for pulling to one side or vibration through the steering wheel. Review MOT advisories for brake-related items.
Rigid brake pipes on B Class models corrode at nearly 10 times the fleet average across all mileage bands including very low-mileage examples. The steel brake pipes run from the master cylinder to each wheel and are vulnerable to corrosion from road salt and moisture. Corrosion can cause sudden brake failure when pipes rupture under pressure.
Corroded brake pipes can rupture without warning, causing sudden brake failure and making the car extremely dangerous to drive. Complete loss of braking ability can occur, particularly under heavy braking when system pressure is highest. Immediate repair is essential for safety.
Check brake disc condition for lipping or scoring. Test braking at moderate speed for pulling to one side or vibration through the steering wheel. Review MOT advisories for brake-related items.
Diesel B Class models experience fuel pipe and hose damage at rates over 40 times the fleet average, particularly from 60,000 miles onwards. The fuel system includes both rigid pipes and flexible hoses that connect the fuel tank to the engine. Deterioration appears linked to diesel fuel chemistry or system pressure characteristics specific to these engines.
Fuel leaks create a fire risk and environmental hazard. Damaged fuel lines can cause fuel starvation, leading to poor running or complete engine shutdown. Repair requires identification and replacement of affected fuel system components.
Check for fuel smells around the engine bay and underneath the car. Look for staining or wetness around fuel lines and connections. Injector issues may cause rough running or misfires that are most noticeable at idle.
B Class models show exceptionally high rates of suspension joint dust cover deterioration, failing at over 25 times the fleet average. These rubber boots protect ball joints, track rod ends, and CV joints from dirt and moisture ingress. Once damaged, contamination enters the joint leading to accelerated wear and eventual replacement of the entire component.
Failed dust covers allow dirt and water into suspension joints, accelerating wear. CV joint boots that fail will require complete driveshaft replacement if left too long. Early replacement of just the dust cover is much cheaper than waiting for the joint itself to fail.
Listen for knocking, clunking or rattling over bumps during the test drive. Inspect the underside for corroded or cracked suspension components. Check the MOT history for suspension-related advisories, which often predict future failures.
Petrol B Class models experience engine mount failure at nearly Engine mounts use rubber-to-metal bonding to isolate engine vibration from the chassis. Failure causes excessive engine movement, transmission of vibration to the cabin, and potential damage to connected pipes and cables.
Failed engine mounts cause increased cabin vibration, potential damage to engine bay components from excessive movement, and accelerated wear of remaining mounts. Multiple mount failure can damage exhaust connections, wiring harnesses, and cooling hoses. Replacement prevents further damage to connected systems.
Check all auxiliary systems during the test drive — air conditioning (both hot and cold), engine mounts (excessive vibration at idle or clunking when pulling away) and all belt-driven accessories. Listen for squealing or chirping from the belt area.
For the full breakdown of all 5 tracked issues with repair costs, see the Mercedes-Benz B Class common problems page.
Routine servicing (oil and filter change every 16k miles) typically costs £120–£180 at an independent garage.
See the full Mercedes-Benz B Class service schedule for every interval and cost breakdown.
The Mercedes-Benz B Class has some well-documented weak points, including 2 safety-critical issues that demand careful checking. The right example, properly maintained, can still be a sound purchase — but cutting corners on the pre-purchase inspection is not advisable. 2019-2022 W247 models offer MBUX infotainment, improved refinement, and the most modern safety tech. Avoid early W246 cars where electrical niggles were more common.
Before committing, check the car's full MOT history, verify the service record is complete, and if possible arrange a specialist inspection. Enter any registration into our free report to see the complete picture.
Get Car Wise maintains a database of known mechanical issues for every popular car on UK roads, tracking the faults that owners, specialists and DVSA data reveal.
When you run a report on a specific Mercedes-Benz B Class, we cross-reference the exact variant, engine and age against our database of 5 known issues. Combined with full MOT history analysis, mileage verification and DVLA data, you get a complete picture before viewing.
Enter the registration for MOT history, mileage verification, known faults for that exact variant, and a Get Car Wise Score.
This guide was compiled from independent expert reviews, DVSA MOT data, specialist workshops and our own database of 5 known Mercedes-Benz B Class issues. We are not affiliated with any source listed.