Mercedes-Benz S-Class S 450 4MATIC Coupé common faults.

2018–2020, coupé, petrol, 367 HP.

The fault list covers: M256, M276DE30AL engine, MB7229, MB7250 transmission.

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5 fault write-ups. All are important. 16 recalls.

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

Before you buy

Known faults

5 important faults

critical1

M271, M272, M273: a leaking camshaft adjuster magnet and oil in the wiring harness

critical

The solenoid of the camshaft adjuster is sealed from the factory by nothing more than a plain sealing ring, and over time that starts to leak. The maker's own bulletin names two places: if the leak is between the solenoid and the cylinder head, the sealing ring has to be replaced, and if it comes through the electrical connector, then the solenoid itself.

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The more serious trouble is at the connector. Through it the engine oil gets into the engine wiring harness and travels under the insulation by capillary action, so it reaches the engine control unit and other important parts as well. The loss of the control unit is the end of that road, and serious engine damage can follow; alongside the contaminated harness the most varied fault messages can appear. Cases have been reported where the oil ran out of the connector, and the consequential damage after that was already large.

The check is simple: the connector of the solenoid has to be taken off and looked at to see whether it is oily. In the fault memory a faulty solenoid gives one of the codes 0059, 0060, 0063, 0064, 0271, 0272, 0275 and 0276. One thing is worth knowing: according to the maker only the solenoid that has a corresponding code has to be replaced, so if a workshop has changed all four of them alongside two codes, that is worth asking about.

The engine number decides what is in the car. Above engine number 2729..30 759427 (M272) and 2739..30 193592 (M273) the maker already fitted the improved solenoid, under part number A272 051 01 77. The oil-leaking solenoid is a problem on engine numbers below 2729..30 895140 and 2739..30 236360.

The prevention is the oil stop cable, which has to be fitted between the solenoid and the harness: the two wires contain a sealed copper sleeve covered with heat-shrink tubing, and that stops the oil from travelling further. It is available from the factory and is not expensive: the two solenoids were around 33 euros and the two oil stop cables around 31 euros, while replacing the control unit is a four-figure sum.

between 90,000 and 130,000 kmfrom 31 EUR

What to check

Ask whether an oil stop cable has been fitted between the camshaft solenoids and the harness
Ask for a check: taking the connector off the solenoid shows whether it is oily
Read the fault memory and look for codes 0059, 0060, 0063, 0064, 0271, 0272, 0275 and 0276

3 more steps in the write-up

expensive4

Cold start rattle: the chain tensioner and the camshaft adjuster drain

expensive

At a cold start a brief, metallic rattle comes from the front of the engine, and it has two causes. With the engine stopped the oil drains out of the passages of the timing chain tensioner, so at start-up the tensioner begins dry, and until the pressure builds back up the chain rattles. The camshaft adjuster rattles for the same reason.

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The rattle lasts one to two seconds and then goes quiet, and that length is exactly what matters. A rattle of a couple of seconds points to the tensioner and the adjuster, not to a chain that has jumped. The control unit logs a code to match: a timing deviation, not a jumped chain.

It is not only the mileage that marks out the affected cars. The maker issued a service document for this in June 2013, and in it the examples with an engine number below 276 8xx 30 001281 or 276 9xx 30 406603 are the affected ones; that runs up to production in February 2013. The fault is also reported between 60 000 and 100 000 miles, that is between roughly 96 000 and 160 000 kilometres. Repairing the chain tensioner costs between 900 and 1300 pounds and the camshaft adjuster between 700 and 1100 pounds, and long cranking and misfires belong to the second job as well.

If it is left like this, the timing fault codes become permanent, the idle turns uneven, power drops and the repair grows larger. The diagnosis runs on live data: the workshop reads the real timing angle and looks at the freeze frame of the fault code.

between 96,000 and 160,000 km

What to check

Start it cold and time how long the rattle lasts: one to two seconds points to the tensioner and the adjuster
Check the engine number: the examples below 276 8xx 30 001281 and 276 9xx 30 406603 are the affected ones
If the knock lasts for minutes and fades as it warms, it is not this but cylinder bore wear

4 more steps in the write-up

7G-Tronic (722.9): mechatronics and conductor plate

expensive

In the Mercedes 7 speed 722.9 automatic (7G-Tronic / 7G-Tronic Plus) the mechatronics unit and the conductor plate (Leiterplatte) age over time: jerking on shifts, delayed engagement, a "Getriebe schützen" message, and fault codes on the gearbox electronics.

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The repair is typically replacing the mechatronics unit or the conductor plate together with an oil change: not the whole gearbox. The complaint is most common on the longitudinal platforms from around 2005 to 2015 (C/E/ML and the early GLC).

The 9G-Tronic (725.0) is a different design; this applies only to the 7G.

between 100,000 and 220,000 km

What to check

Try it cold and warm: a delayed 1 to 2 or 2 to 3 shift is suspect
Watch for the gearbox warning or the "Getriebe schützen" message on the dash
Ask for a fault code read on the gearbox controller (not just the engine codes)

1 more steps in the write-up

Airmatic air suspension: leaking air spring, overworked compressor

expensive

The Mercedes Airmatic system holds the ride height with air springs and electronically controlled dampers. The most common faults over time are the relay, the compressor and a leaking air spring or air line.

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The rear air springs of the 2003 to 2009 E-Class (W211) are particularly prone to leaking along the clamps. If the system leaks, the compressor runs continuously, overheats and fails, so an unrepaired leak takes the compressor with it.

Symptoms: one corner of the car sinks by morning, an "Air Suspension" or level control fault message, and compressor noise while standing. It was an option (or standard) across several generations from the W220 S-Class onwards; the estate E-Class often has air springs with level control on the rear axle as standard.

between 100,000 and 220,000 km

What to check

In the morning, before setting off, look at all four corners: an uneven stance means a suspected leak
With the car standing, listen to the compressor: continuous running indicates it is overworked
Ask for a fault code read on the suspension controller (level and pressure sensor codes of the C1132 / C1144 kind)

3 more steps in the write-up

Oil cooler seal in the V valley: the oil and the coolant mix

expensive

The oil cooler sits in the V valley between the cylinder banks, under the intake manifold, where the oil circuit and the coolant circuit meet. Its seal ages, and from then on it leaks along two paths. Outwards the oil collects in the V valley, runs down and leaves traces on top of the engine and around the intake manifold, so for a long time all that shows of it is that the oil level falls. Inwards the two fluids mix into each other.

Show the rest

The signs of the mixing are clearly visible. A mayonnaise-like, frothy deposit appears on the oil filler cap and on the dipstick, an oily film settles in the expansion tank, and the coolant level falls with no external leak. White smoke from the exhaust can come with it, overheating without any visible loss of fluid, and uneven running.

Once the seal has started, the leak accelerates. A few weeks of inattention is the difference between a seal replacement and a rebuild with connecting rod bearings, because oil diluted with coolant does not lubricate the bearing.

The repair costs between 1700 and 3800 euros and is a one to two day job: the cooler can only be reached after the intake manifold has been removed and the engine partly disassembled. The labour makes up the price, not the part.

1,700–3,800 EUR

What to check

Unscrew the oil filler cap and pull the dipstick: a mayonnaise-like, frothy deposit means mixing
Look into the coolant expansion tank: an oily film on the top belongs here
Ask how much coolant has to be topped up: loss with no external leak gives it away

3 more steps in the write-up

Official recall16 recallsShow

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

Most recent: 20 May 2022

22V365000ELECTRICAL SYSTEM:SOFTWAREELECTRICAL SYSTEM:SOFTWARE20 May 2022 · NHTSA (USA)

Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2017-2022 CLA-Class, GLA-Class, GLE-Class, GLS-Class, SLC-Class, A-Class, AMG GT-Class, C-Class, E-Class, S-Class, SL-Class, GLC-Class, CLS-Class, GLB-Class, and G-Class vehicles. Please refer to MBUSA's recall report for specific vehicle model details. An error in the communication module's SIM card software can cause a mobile network connection failure, disabling the emergency call (eCall) system.

Risk: A disabled eCall system would prevent a vehicle occupant from contacting the emergency services call center in an emergency, potentially delaying emergency responders and increasing the risk of injury.

Remedy: The communication module software will be updated through an Over-the-Air (OTA) update or by a dealer, free of charge. Owner notification letters were mailed July 8, 2022. Owner notification letters will be mailed in phases, on July 8, 2022, May 17, 2024, July 29, 2024, and September 27, 2024. Owners may contact MBUSA customer service at 1-800-367-6372. MBUSA's numbers are for this recall is 2022060005 and 2023110006.

Mercedes-Benz S-Class S 450 4MATIC Coupé common faults.

Known faults

critical1

M271, M272, M273: a leaking camshaft adjuster magnet and oil in the wiring harness

expensive4

Cold start rattle: the chain tensioner and the camshaft adjuster drain

7G-Tronic (722.9): mechatronics and conductor plate

Airmatic air suspension: leaking air spring, overworked compressor

Oil cooler seal in the V valley: the oil and the coolant mix

Checklist

On every car

Ask the owner

Faults of this model

Engine and transmission

M256

MB7229 · 7G-Tronic / 7G-Tronic Plus, longitudinal (Mercedes 722.9 / NAG2)

What is in this version

Factory data

Factory service interval

Information, not an expert opinion

`M256`

`MB7229` · 7G-Tronic / 7G-Tronic Plus, longitudinal (Mercedes 722.9 / NAG2)