Mercedes-Benz A-Class Common Problems & Known Faults (UK)
If you are considering buying a used Mercedes-Benz A-Class, there are several major reliability issues worth knowing about first. Our garage database tracks 13 known faults for this model, 8 of them rated high severity. Every one below is a repair bill a seller has good reason not to mention.
Are you about to buy a lemon?
Sellers rarely admit these faults outright. Our database tracks 38 specific phrases sellers use in adverts to soft-pedal these exact issues. Paste any Mercedes-Benz A-Class advert and we will check it in seconds.
Timing chain stretch and leaking hydraulic tensioners on the M270 turbo petrol. The chain rattles on cold start as the tensioner loses oil pressure; left alone the plastic guides wear, the chain can skip a tooth and throw camshaft timing codes (P0016/P0017 family), and in the worst case the valves contact the pistons. The transverse installation in the A-Class makes the repair far more labour-intensive than on rear-drive Mercedes, so UK specialist quotes run 1400-2000 pounds
Rough guide
£1400-2500
Typical symptoms
metallic rattle from the engine for several seconds on cold start-up
engine management light with camshaft timing fault codes
rough running or misfire once the chain has jumped
Affected vehicles
Engines:
1.6 / 2.0 Turbo Petrol (M270)
Typical mileage:
50000-100000 miles
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The 7G-DCT dual-clutch automatic suffers low-speed judder and jerky shifts as the wet clutch packs wear, and mechatronic (electrohydraulic control unit) failures that cause delayed engagement, harsh 2nd-3rd shifts, limp mode or loss of drive. Mechatronic replacement is quoted at 1200-1800 pounds by UK specialists; clutch pack replacement is similar. Neglected 40k-mile fluid changes accelerate both
Rough guide
£1200-2500
Typical symptoms
shuddering or juddering when pulling away from a stop
hesitation or a lurch when setting off, worse when cold
clunk into P, N or R, or harsh low-gear shifts
gearbox warning and limp mode in advanced cases
Affected vehicles
Engines:
All with 7G-DCT dual-clutch automatic (Getrag 724.0)
Typical mileage:
50000-100000 miles
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The 722.8 Autotronic CVT's internal gearbox ECU fails (speed sensor circuits break down inside the sealed unit), throwing 'Transmission Visit Workshop' on the dash and dropping the car into limp mode with limited or no gear selection. A main dealer fix means a new ECU, valve body and coding at well over 1000 pounds; even specialist ECU rebuilds with fitting typically run 500-1000 pounds
Rough guide
£600-2000
Typical symptoms
'Transmission Visit Workshop' warning on the dash
sudden limp mode or loss of drive
harsh or absent gear engagement, stuck in one ratio
Affected vehicles
Engines:
All with CVT automatic (722.8 Autotronic)
Typical mileage:
60000-120000 miles
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The multi-section sliding steel sunroof is highly prone to failure. If the motor on one side fails, the other motor skews the panels and the whole mechanism seizes up, leading to a very expensive repair.
Rough guide
£1000-2000+
Typical symptoms
Sunroof panels skew or jam when opening/closing
Sunroof fails to open or close completely
Grinding noises from sunroof mechanism
Affected vehicles
Engines:
All variants with multi-section sliding steel sunroof
Typical mileage:
50000-100000 miles
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Fuel SystemHigh severity📝 Editorial
Widespread problem of fractured fuel filler pipes, leading to petrol leaking into the rear of the car if the tank is over-filled. Further reports of fuel pipes weeping at the bulkhead areas on 6-year-old petrol models.
Rough guide
£300-600
Typical symptoms
Smell of petrol inside the car, especially after refuelling
Visible fuel leaks around the filler neck or rear of the car
Fuel gauge inaccuracies
Affected vehicles
Engines:
Petrol models
Typical mileage:
60000-100000 miles
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Transmission/ClutchHigh severity📝 Editorial
Automatic transmission failures requiring new transmissions are common on A-Class models more than 4 years old, with reported costs of £5,000+. This often exceeds the value of the car. There are also reports of loss of power when setting off from standstill, which can be a revised transmission governor or a sticking stop light switch.
Rough guide
£5000+
Typical symptoms
Complete loss of drive
Car locked in a single gear (e.g., 2nd gear)
Loss of power when setting off from standstill
Jerking or harsh shifts
Affected vehicles
Engines:
All automatic transmissions
Typical mileage:
40000-80000 miles
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Engine/EmissionsHigh severity📝 Editorial
Diesel glow plugs have a habit of failing and then breaking when garages attempt to remove them, leading to rectification costs of up to £4,500. This is particularly an issue for cars used for repeated short runs from cold.
Rough guide
£500-4500
Typical symptoms
Difficulty starting the engine, especially in cold weather
Engine misfires or runs rough on startup
Glow plug warning light illuminated
Affected vehicles
Engines:
All diesel engines
Typical mileage:
60000-100000 miles
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Significant problems with rust perforation, particularly on door bottoms, tailgates, and A-pillars. This can be due to weld seal failures on hatchbacks or paint rubbing on A-pillars from plastic front wings. Mercedes-Benz may offer goodwill payments but often rejects 'no perforation' warranty claims due to 'external influences'.
Rough guide
£500-3500
Typical symptoms
Visible rust bubbles or perforation on door bottoms, tailgate, or A-pillars
Paint flaking or bubbling in affected areas
Disputes over warranty claims for rust
Affected vehicles
Engines:
All models
Typical mileage:
60000-100000 miles
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On diesel manual models that undergo a lot of gear changing, the clutch spline can dry out, leading to 'sticking' in gear if left with the clutch down when stopped. This requires regular greasing or replacement of the clutch assembly.
Rough guide
£300-800
Typical symptoms
Clutch pedal feels stiff or sticky
Difficulty selecting or disengaging gears
Car 'sticks' in gear when clutch is depressed at a standstill
Affected vehicles
Engines:
Diesel manual transmissions
Typical mileage:
40000-80000 miles
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Water ingress into the load area and rear footwells is a common problem, caused by failing one-way rear cabin vent flaps. These flaps, located between the load area sides and the rear bumper extensions, allow water splashed by the back wheels to enter the cabin. Repair can be costly, involving bumper removal and sealing.
Rough guide
£500-1500
Typical symptoms
Sodden rear footwells or load area
Damp carpets in the boot or rear cabin
Musty smell inside the car
Visible water accumulation in the spare wheel well
Affected vehicles
Engines:
All models
Typical mileage:
40000-80000 miles
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OtherMedium severity💬 Owner reports
The clearcoat lacquer over red paint finishes (such as 'Juniper Red' and 'Fire Opal Red') has been reported to fail, leading to dulling, peeling, or fading of the paintwork. This is a cosmetic issue but can be expensive to rectify.
Rough guide
£500-1500
Typical symptoms
Dulling or fading of red paintwork
Clearcoat peeling or flaking, especially on horizontal surfaces
Patches of discoloured or chalky paint
Affected vehicles
Engines:
Models with red paint (e.g., Juniper Red, Fire Opal Red)
Typical mileage:
40000-80000 miles
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Repeated failure of the driver instrument display, frequently not switching on and leaving a black screen. This prevents the driver from viewing essential information such as speed, fuel gauge, and gear selection, posing a safety risk.
Rough guide
£800-1500
Typical symptoms
Driver instrument display remains black after starting the car
No speed, fuel, or gear information visible
Intermittent display functionality
Affected vehicles
Engines:
All models with digital instrument display
Typical mileage:
0-10000 miles
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A broken steering column spring, coupled with insufficiently earthed wiring, may lead to a short circuit and inadvertent deployment of the driver's airbag. This was subject to a voluntary recall by Mercedes-Benz.
Rough guide
£0 (free safety recall)
Typical symptoms
Airbag warning light appearing on the dashboard
Unexpected airbag deployment
Affected vehicles
Engines:
All variants
Typical mileage:
All mileages miles
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Mercedes-Benz A-Class service intervals: cambelt, chain and gearbox oil
An overdue cambelt is the most expensive thing a seller can fail to mention on a used A-Class. These are the figures UK specialists work to.
Timing belt (cambelt)Belt
1.5 DCI, 1.5 CDI, OM607, K9K
60,000 miles or 5 years, whichever comes first
Renault-sourced engine, and the engine maker's guidance is the shorter one: Renault specifies the belt at 60,000 miles or 5 years, whichever comes first, while a Mercedes dealer schedule quoted 100,000 miles / 5 years and was later revised to 124,000 miles / 10 years. The 60,000-mile Renault figure is recorded. Rubber degrades with age so the 5-year limit is the critical one.
Timing chainChain
M270, M274, 1.6 TURBO, W176, W246
No fixed replacement interval
Dual-stage chain system: an upper cam chain plus a lower oil-pump and balance-shaft chain. Cam phasers (Y49/1, Y49/2) wear from around 60,000-80,000 km giving a cold-start tick; chain and guide wear shows from about 80,000 km on urban short-trip cars but 120,000-140,000 km on motorway cars. A metallic cold-start rattle needs prompt attention. The M274 DE16 is the longitudinal C-Class version of the same 1.6.
Always confirm against the vehicle handbook. Intervals vary by engine, and several manufacturers revised theirs after failures in service.
Repair costs are typical UK ranges, not quotes. Actual cost depends on condition and garage.Data last verified: September 2026
Where this Mercedes-Benz A-Class fault data comes from
If you used to check the Honest John “Good & Bad” section before the site closed in 2026, this page is where that information now lives. We rebuilt the Mercedes-Benz A-Class owner-report history from the archived Honest John dataset, added our own research, specialist and owner-club sources and DVSA recall data, and we keep it free. Each fault above is badged with its source. The same data feeds our free advert check, which reads a listing against every known fault for the exact engine and year.
Knowing what a Mercedes-Benz A-Class goes wrong with is half of it. The rest is reading the advert and checking the car's history before you hand any money over.