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Mercedes Benz B Class Problems & Known Issues

The most common Mercedes Benz B Class problems ranked by severity — what to watch for, what it costs to fix, and what happens if you ignore it.

Generations

W245 — First Generation
2005–2011
B150, B170, B200, B200 CDI
W246 — Second Generation
2011–2018
B160, B180d, B200d

Top issues to watch for

The most serious Mercedes Benz B Class problems ranked by severity. We track 5 known issues — here are the ones you need to know about first.

Dangerous
Brake hose deterioration (all generations)
W245, W2462005–20180k–150k miles
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.
What happens if ignoredBrake 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.
Independent garage
£80–£150
Specialist
£120–£200
Main dealer
£180–£280
Parts only
£25–£50
Dangerous
Brake pipe corrosion (all generations)
W245, W2462005–20180k–150k miles
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.
What happens if ignoredCorroded 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.
Independent garage
£150–£300
Specialist
£200–£400
Main dealer
£300–£500
Parts only
£30–£80
Major
Fuel system deterioration (diesel)
W245, W2462005–201860k–150k miles
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.
What happens if ignoredFuel 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.
Independent garage
£150–£400
Specialist
£200–£500
Main dealer
£300–£700
Parts only
£50–£200
Minor
Suspension joint dust cover failure (all generations)
W245, W2462005–201820k–150k miles
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.
What happens if ignoredFailed 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.
Independent garage
£60–£120
Specialist
£80–£150
Main dealer
£120–£200
Parts only
£15–£40

1 more known issues tracked

Including wear items, electrical niggles, and generation-specific problems.

Looking at a specific Mercedes Benz B Class?

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Related

Mercedes Benz B Class reliability FAQs

What are the most common problems with the Mercedes Benz B Class?

The Mercedes Benz B Class has 5 known issues across 3 severity levels. The most serious are: Brake hose deterioration (all generations), Brake pipe corrosion (all generations).

Is the Mercedes Benz B Class reliable?

The Mercedes Benz B Class has 2 dangerous and 1 major known issues. Most can be avoided with a thorough pre-purchase check and full service history.

How much does it cost to fix Mercedes Benz B Class problems?

Repair costs range widely. The most significant issue (Brake hose deterioration (all generations)) costs £80–£150 at an independent garage. Minor issues can be under £200. Always get a full inspection before buying.

Which Mercedes Benz B Class generation is most reliable?

The W245 (2005–2011) has the fewest dangerous issues (2). However, condition and service history matter more than generation — a well-maintained earlier car can be more reliable than a neglected newer one.