Mercedes-Benz A-Class A 180 Business Solution AMG common faults.

2015–2018, hatchback, petrol, 122 HP.

The fault list covers: M270DE16AL engine, MB6MT-MFA transmission.

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6 fault write-ups. All are important. 7 recalls.

If you know the year, pick it. Faults for other years drop out of the list.

Before you buy

Known faults

6 important faults

critical4

M270: a stretching timing chain with an undersized tensioner

critical

The timing chain stretches from 80,000 kilometres, and the cause is the exhaust-side chain tensioner: it is undersized and does not hold the chain properly. Short city use speeds the process up.

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The symptom is a rattle on a cold start. The stretched chain makes the timing slip, and if the chain jumps, the valves and the pistons meet.

above 80,000 km

What to check

Start it from cold and listen to the first seconds: a rattle points at the chain
Check whether the noise stays when warm: a chain fault does not fade with warming
Ask what kind of journeys it did: short city use speeds up the wear

2 more steps in the write-up

Timing chain: the pulse wheel shifts, and the chain stretches with it

critical

The service life of the timing chain on this engine is not outstanding: it has to be replaced between 100 000 and 150 000 kilometres. The stretching, however, is accelerated by another part, and that is worth knowing.

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The pulse wheel is press-fitted onto the camshaft, and it shifts a little with every start. That shifting significantly speeds up the stretching of the chain.

The symptom is difficulty starting, which can grow as far as complete failure. The engine starts hard when cold, and as the valve timing drifts it loses power.

The repair is therefore not just the chain: the stretched chain and the faulty pulse wheel have to be replaced together. If only the chain is renewed, the cause stays in place and the next chain stretches the same way. So look for both of them on the invoice.

On engines built before 2014 the phase regulators also failed quickly and started to crack. The maker revised them, which pushed the fault later, but did not eliminate it.

between 100,000 and 150,000 km

What to check

Start it cold: difficulty starting points to a stretched chain and a shifted pulse wheel
Ask for the invoice of the chain change and check whether the pulse wheel was replaced too
Listen to the engine cold: chain noise comes from the front of the engine

2 more steps in the write-up

Faulty weld seam on the camshaft: a recall, free replacement

critical

On engines built between July and September 2015 the supplier made a mistake in the welding process, so the weld seam on the camshaft is not as it should be. According to the authority's notice the fault affects individual M270 and M274 four-cylinder petrol engines.

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On the affected cars the camshaft can break, and in doing so it damages the engine and shuts it off. The engine cannot then be restarted, the car comes to a halt, and in the words of the notice this increases the accident hazard.

As a precaution the maker prescribed replacement of the camshafts. The campaign started in November 2015, the target date for completion was the end of 2016, and the replacement is free for the owner.

At a purchase two things have to be cleared up: does the car fall into the production window, and if so, has the recall been carried out on it. The franchised dealer can answer that from the chassis number.

What to check

Check the production date of the engine: the examples from between July and September 2015 are affected
Ask whether the recall has been carried out, and ask for proof of it
If there is no proof, ask the franchised dealer with the chassis number: they can tell you

2 more steps in the write-up

M270: a faulty weld seam on the camshaft, recall

critical

In engines built between July and September 2015, the weld seam on a camshaft lobe can be faulty and the lobe can break off.

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With a broken lobe the affected valve does not open, the engine runs unevenly, and the broken piece causes damage inside the engine. The manufacturer issued a recall and the replacement is free.

What to check

Check the engine build date: units built between July and September 2015 are affected
Ask whether the recall was carried out, and ask for proof
At idle, watch the engine: it must not run unevenly or misfire

1 more steps in the write-up

expensive2

M274 2.0 turbo: crankcase ventilation (PCV) control valve failure

expensive

On the 2.0 turbo four cylinder (M274, and the transverse M270) the control valve of the crankcase ventilation system fails early. The official database holds 259 reports on it, almost exclusively on the 2015 to 2019 C 300 and GLC 300 versions.

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The symptom: the engine warning light comes on, and diagnostics returns a fault code complaining about crankcase ventilation valve performance. Alongside it you get a fluctuating idle, a whistling or sucking noise from the engine bay, and sometimes harder starting.

The valve is part of the intake system, and if it sticks open or closed the engine either draws false air or the pressure in the crankcase rises. The latter pushes the crankshaft seals out, and from then on you have an oil leak. The valve itself is a cheap part, but getting to it is not always cheap.

On the same engine generation the complaints also include 27 reports of a cracked piston (weighted to the C 300 in 2015 and 2017). That is much rarer. If the engine burns oil or knocks, do not think only of the ventilation valve.

The official data is American, and the 2.0 petrol is far more common there than in Europe.

between 64,000 and 145,000 kmreported complaints only

What to check

Ask for a fault code read and look for the code on crankcase ventilation valve performance: that is the characteristic entry
Listen to the engine bay at idle: a whistling, sucking noise points to a torn valve diaphragm
Look around the valve cover and the crankshaft seals for oil leaks: the consequence of raised crankcase pressure

2 more steps in the write-up

M270: a failing electric thermostat leaves the engine cold

expensive

The electric thermostat can fail from 90 000 kilometres and sticks open. The coolant then circulates in the large circuit even while the engine should still be warming up, so the engine does not reach its 80 degree operating temperature.

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The control unit logs it too: code P0128 means that the coolant temperature stays below the regulating temperature of the thermostat. The symptom is that the engine does not warm up properly even after a long time, the heater is lukewarm, consumption rises and the engine management light comes on as well.

An engine running cold for a long time wears faster, because cold oil does not lubricate the same way and fuel dilutes it in a greater proportion. The thermostat is built into the coolant circuit, so its replacement involves draining coolant.

above 90,000 km

What to check

Run the engine for ten minutes: the temperature gauge has to reach its usual middle value
Turn the heating on: the air should be hot, not lukewarm
Have the fault codes read and look for P0128

2 more steps in the write-up

Official recall7 recallsShow

The manufacturer fixes these for free at a franchised dealer. Ask with the VIN whether it was done.

Most recent: 1 September 2017

A12/1352/17Safety recallFire1 September 2017 · EU Safety Gate

The starter current limiter may be overloaded and overheat. As a consequence, the surrounding components could ignite, leading to a fire.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: 01/09/2017

The authority's notice

A12/00017/22Safety recallFireno date · EU Safety Gate

A trapped particle may damage the sealing between the fuel rail and fuel injector, which could cause fuel to leak into the engine compartment. Consequently, leaking fuel may come into contact with hot parts of the engine, increasing the risk of fire. The product does not comply with the requirements laid down in the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.