Mercedes S-class (W221) 2006-2013

Petrol engines

The petrol engines are definitely not unreliable but there are a couple of weak and weaker points.

Let’s start with something minor and not that expensive to fix. Engine mounts! The engine mounts in these cars are made from chocolate so they can easily compress, or fall apart completely even before 70 000 mi. In this case you get vibrations at idle or at acceleration, and also while in gear standing on the brake pedal. By the way the transmission mount can fail prematurely as well so keep extra money to replace it too.

ruined engine mounts video example

replacing the engine mounts on a S500/S550 can cost up to $3 000 at the dealer, but approx. $600 at an independent mechanic

V6 and V8 to 2010 (M272, M273)

balance shaft sprocket failure

-The well known balance shaft sprocket failure can occur in cars made to 2007. Mostly the V6 M272 engines are affected but the V8 M273 engines can have occasionally worn gears as well. Because of the worn gear the timing chain gets loose which will cause misfires, an illuminated check engine light with stored fault codes, eventually a rattling noise from the engine and at the end the chain will skip which will most probably destroy the engine.

Replacing the faulty parts is not cheap mainly because the engine has to be removed, so all in all it’s simply better to avoid the cars made to 2007 and buy a car made from 2008 which has the updated gear. However some cars made in late 2007 can have the updated parts fitted as well so if you found a car from this time period then you should check the engine serial number if it’s in the affected range or not. But of course if the previous owner replaced the sprocket and the timing chain then you can buy an earlier car.

website for checking the balance shaft issue affected range of engines

variable intake manifold

-The next problem which affects all the V6 M272 and V8 M273 engines is related to the complex variable intake manifold. Basically a plastic arm on the outside can break or sometimes the plastic flaps inside the intake manifold can fall apart as well causing: misfires, loss of power and eventually an illuminated check engine light. The broken outside plastic arm can be fixed by replacing it with an improved metallic one, however in this case it’s also good to remove and clean the intake manifold itself, because there will be most probably a bigger or smaller amount of carbon deposit in it.

On the other side the simplest and fastest solution is to buy a new complete intake manifold- since after replacing the outside arm only and cleaning the intake manifold, the inside plastic flaps in it can still break.

Improved metallic outside arm with new gaskets – 110 € / $125

New complete intake manifold – from 500 € / $566 (replacing it at the dealer – 2 200 € / $2 500)

camshaft adjustment solenoids

-Then there are 4 cam adjustment solenoids which can leak oil or they can also fail, again on the already mentioned M272 and M273 engines. If they start to fail then you will experience various symptoms like: an illuminated check engine light, stored fault codes or even loss of power, poor idle/misfires, eventually stalling.

The solenoids are located on the front of the engine so replacing them is not very hard and luckily they are also not expensive. how to replace these solenoids

+ more info of other sensors which can fail on these engines

how to replace the spark plugs S550 V8 2006-2011

V6 and V8 to 2010 bonus issue (M272, M273)

Before I continue with the newer engines, I have to mention the cases of worn cylinder walls in these M272 and M273 engines. Listen, this issue is NOT very common so don’t panic. However if:

• the previous owner used incorrect oil
• it is a higher mileage car with too long oil change interval
• if the engine has a long lasting issue with leaking fuel injectors
• or if the engine has a long lasting issue with vacuum leaks-which lead to incorrect detonation thus increasing the temperature in the combustion chamber

THEN yes, the engine can have worn cylinder walls causing oil consumption, misfires, loss of compression, knocking noise, and destroyed engine.

V6 and V8 from 2011 (M276, M278)

Next there are the newer versions of these engines. The V6 M276 remained without a turbocharger, while the M278 V8 got 2 turbochargers. This translates to 435 hp and 700 NM of torque which is more than enough. Interestingly the turbochargers in this V8 are usually reliable, unless of course the car was abused, used only on short distances or it has high mileage. + Rarely a rod above the turbo can break causing loss of power and the 0299-turbo under boost – fault code.

this engine has to be removed from the car to replace the turbochargers, so be prepared to pay thousands, thousands and thousands when they fail: approx. $9 000 in total to replace 1 turbocharger and remove engine

So the turbochargers are usually ok, however what is not really ok is, that these 2 engines can develop a short rattling noise at cold start which is caused by the loose timing chain tensioners. Because of this the chain can stretch prematurely which is not good. So, to fix this you have to replace the tensioners and additionally fit a small check valve into the cylinder head oil supply bore-directly behind the tensioner.

But if the rattle persists then you should replace also the camshaft adjusters which can be faulty, and this step should finally solve the rattle!

This is how the engine should sound during startup – start up video without rattle

Also keep in mind that these newer engines are equipped with direct injection so generally speaking there should be a higher chance of faulty injectors or carbon build up. But in this case there are not many issues with the injectors and the carbon build up on the intake valves is usually not major either. This of course doesn’t mean that there is none of these issues so it’s still good to practice the following things to minimize the carbon build up in high mileage cars: use only high quality premium fuel, use the car on long distances too, change the engine oil after max. 8 000 km, and don’t be afraid to occasionally rev the engine properly-after warming it up of course.

To minimize issues with the turbochargers don’t use the start-stop system, don’t use this engine only for short city driving, and after a more dynamic driving keep the engine running at idle for at least 30 seconds before shutting it off.

All in all, with the proper care and mainly if you change that damn oil after 8 000 km, these engines can without bigger issues last up to approx. 200 000 km. After this mileage point, or on lower mileage abused cars with performance upgrades there is a high chance that the engine will have increased oil consumption:

V8 from 2011 ( M278) Bonus Issue

There can be an interesting issue with increased oil consumption because of worn cylinder walls and faulty pistons in this newer V8 engine. In this case the engine can develop a funny rattling/knocking noise as well which in other words means: EXPENSIVE REPAIR.

broken M278 idle knocking noise video

So if you hear the above noise from the engine then be ready to have it completely repaired – the price for this engine repair is somewhere around 5 000 € – 10 000 €.

But all of this stuff is not like extremely common YET. Nevertheless, it’s really important to avoid a car with this engine which has a performance upgrade-because this is the main reason for the worn cylinder walls and faulty pistons issue, and change that damn engine oil after MAX. 8 000 KM / 5 000 mi !!

The same goes for the S63 AMG with the M157!

S 600 V12

-The next on the list is the massive V12 with two turbochargers. It is awesome, it’s powerful, it’s not equipped with direct injection which is good, and there are also no major mechanical problems with it. However life is not a fairy tale so the maintenance of this engine is obviously more expensive. Or in other words, there is a high chance that sooner or later it will cost you bigger amount of that currency.

For example, this engine has 2 spark plugs/cylinder so there are 24 of them in total. This means that replacing them is obviously a bit more expensive and time consuming than on a regular V8. This would not be that big of a deal if the ignition coils would not be special and fucking expensive. The ignition coils are built into a rail which means that if one coil fails then you will have to replace the whole assembly. The new rail is expensive, but you can have it refurbished for a lower price and actually, the failure rate of this coil pack assembly is much lower than in the predecessor. But still, you have to be prepared that it can break, on the other side if you change those damn spark plugs after 60 000 km then you will minimize the failure of that damn ignition coil assembly.

how to remove the ignition coil assembly/replace the spark plugs S600 V12 video

info about refurbishing the ignition coil assembly

Then, if you buy mainly an older before facelift S600 then you have to be ready for various leaks. Some random oil pipe can leak here and there because of the age or corrosion, but that’s not even worth mentioning. On the other hand what is worth mentioning is a common possible leak related to the turbochargers on each side of the engine of course. There are 2 lines on the top of the turbocharger – an oil pipe and a coolant pipe. And the coolant pipe ending can leak. In this case you have to replace only a cheap o ring on the end of the coolant pipe, however you have to remove a bunch of stuff to access it which is time consuming. The only good thing is that there is no need to remove the engine, although the dealer will most probably remove the whole engine to fix this – which will in this case cost you 6,7 or 8 thousand of that currency. By the way in this case you should replace also the seal on the oil pipe, obviously.

Fixing this leak costs approx. $4 500 at an independent mechanic with removing the engine, without removing it should be up to $1 000

However if you are like really unlucky then not the o-rings, but the turbocharger itself can leak coolant from the core/freeze plug. In this case you have remove the engine and replace the whole turbocharger since these plugs are not available separately, but don’t panic since this is not like extremely common. (If you know a cheaper solution to repair this then write it into comments!)

just a funny video what it takes to remove and replace a turbo on this V12

And the next issue? Well there is nothing else really. I mean nothing else which would be special for this particular engine. But definitely check carefully for leaks which can be more expensive to fix, mainly if you are not familiar with this engine.

“Just remember: this engine is complicated, it generates a lot of heat, so some of the other rubber o-rings, gaskets, rubber hoses, pipes, valve cover gaskets can occasionally leak. Fixing these leaks is usually expensive since you have to remove a lot of things and sometimes the whole engine to fix them.”

S 400 Hybrid

The last from the non AMG versions is the S400 hybrid model which has the M272 V6 engine + an additional small hybrid system. This version was made from 2009 so the engine itself is not affected with the balance shaft sprocket failure, but it can have the other already mentioned M272 engine related issues.

And what about the hybrid system components? Well, they are definitely not that reliable as in a Toyota Prius. To top of that, some say that this hybrid version was built just to make the brand look greener/to improve the image of Mercedes, or in other words just to statistically lower the CO2 numbers of the whole S class model range. + just a handful of independent mechanics do actually have a clue what it is, how it works and what are the potential issues of this system

So, some of that weird expensive hybrid stuff can break. And especially the inverter failures are pretty common. The early symptoms of this inevitable failure are: not working start-stop system, long engine crank, occasionally not working AC, fault codes related to the hybrid system and later when the inverter completely breaks – the engine will shut off in the middle of the road and you won’t be able to start it. The new inverter costs around 4 000€, but there are remanufactured inverters from China for half of the price.

Then there is the hybrid battery which is located under the hood, it costs around 8 000 €, and it won’t last forever either. So all in all: if you don’t know somebody who is familiar with this hybrid system and you don’t want to spend thousands to fix it, then just avoid this hybrid version completely.

hybrid – remanufactured inverter from china

hybrid – how to remove the inverter video

AMG

Lastly, let’s briefly check out the AMG versions.

The before facelift S63 AMG made to 2010 has a naturally aspirated 6.2 l V8. This same engines was used in the CLK 63 AMG and in the E63 AMG as well, which means that it can have the well-known issue with the stretched or completely broken cylinder head bolts.

In these engines Mercedes used not the strongest cylinder head bolts which means that they can slightly stretch or break completely-causing leaking head gasket. In this case you will experience coolant loss due to coolant entering the combustion chamber via the blown head gasket and it will mix with oil. If you don’t fix this then you will end up with a destroyed engine, but Mercedes updated these head bolts so you can obviously replace them preventively. You either replace them one by one, without removing the heads and replacing the head gaskets – this is I would say the cheaper preventative solution. Or if you already experienced bigger coolant loss and coolant mixing with oil, then it’s better to remove the heads and replace the head gaskets too-this is obviously much more expensive.

This problem with the bolts is not like extremely common, so there are still even high mileage cars with the factory head bolts. On the other side there are already numerous cases of failed head bolts and some owners just replaced them preventively. At the end it’s up to you. But if the car still has the factory head bolts then you should at least check the coolant level regularly, and if you experience even the slightest coolant loss then first check for leaks, and if it’s not leaking anywhere then you should consider replacing the bolts ASAP.

“By the way, if you have this engine then it’s really REALLY important to have clean engine oil, so change it after maximum 8 000 km / 5 000 mi, and keep the oil topped up to the correct level, because if not – then you are increasing the risk of problems with the camshaft adjuster solenoids or prematurely worn camshafts! (symptoms of faulty camshaft adjusters: rattle at start up, misfires, check engine light)”

The newer S63 AMG made from 2010 has a similar engine as the newer S500, so it has two turbochargers and direct injection and it has the same possible issues as the engine in the S500. The most powerful version of this S class is the S65 AMG which has a modified V12 from the S600 model, and it can have the exact same issues as the engine in the S600.

To end this, keep in mind that there is a bigger chance that all these AMG versions were abused, so the risk of unexpected wear and repairs is increased mainly when you buy one which is not from the first owner.

Diesel engines

320 CDI, 350 CDI

From the diesel engines the most reasonable choice is the 3.0 l V6. The reliability of this unit is not bad – it can withstand 300 000 or 400 000 kms, and I have seen numerous examples with more than 500 000 km as well, so except the usual diesel engine problems it doesn’t have many specific issues. But this doesn’t mean that it’s bulletproof, so there are 2 issues which are more common and which are worth mentioning:

inlet port shut off motor

-The first is related to the inlet port shut off motor or the swirl flap motor in other words. This motor can fail causing limp mode/reduced performance and an illuminated check engine light. This failure is caused by the seal on the turbocharger which will let the oil to slowly drip into this motor. how to fix the motor for free

oil cooler leak

-The next issue is the famous oil cooler leak caused by the seals attached to this oil cooler. You will definitely notice this leak since there will be traces of oil under the car and on the lower engine plastic panel + if you look at the bottom of the engine then you will see the black oil appearing at the rear of the block. Because of the heat the old seals can fail prematurely, and that’s why Mercedes updates these seals. The new updated seals are cheap, but that damn oil cooler is buried deep down in the middle of the engine(-between the heads) so you will have to remove a shit ton of parts to access the cooler(you have to remove various hoses, pipes, random boxes, the turbocharger + the intake manifolds). how to replace the oil cooler seals quick video

250 CDI

The 4 cylinder diesel engine is generally speaking not the best choice mainly because it can have more often issues with faulty injectors and with the prematurely worn timing chain. But long story short, the injectors were most of the time fixed under the warranty or under the recall, although the timing chain was not. However if both of these possible issues were fixed by the previous owner then this engine is definitely not the worst choice either.

420 CDI

The last engine is the big V8 with two turbochargers. Listen, this engine can serve you well unless you buy a car which had travelled to the moon and back or which was not treated properly. But either way, you have to be prepared that because of the bigger complexity and lack of space around the engine, the potential repairs are not going to be the cheapest + except the usual diesel engine problems it can have the exact same oil cooler leak as in the smaller V6, and there are occasionally cases of head gasket failures.

the advantage of this V8 compared to the smaller V6 is the additional power obviously, and also the fact that to replace the oil cooler you are removing less stuff, since the V8 doesn’t have the turbocharger on the top of the engine + there are no issues with the swirl flap motor either

All the diesel engines are equipped with DPF filters and from 2010 the V6 is equipped with the additional fantastic damn Adblue emission system as well. As usual the DPF can clog(this is nothing new), some pressure sensor on it can fail(this is nothing new either), however the additional Adblue system has more additional sensors and issues(and this can be something new even if it’s not).

On the picture below: AdBlue, NO START IN 731 km.

Adblue – this fantastic system can cause some additional issues, you can get various fault codes with the check engine light, the adblue level sensor can show low level even if the tank is topped up(-in this case it’s sometimes enough to recalibrate the sensor), then the adblue NOX sensor can be faulty. So be prepared to deal with this horrible system which is not going to let you start the engine if the adblue tank will be empty, or if the tank will be full but the sensor is going to read empty! Why? Cause the sensor is fuckin broken!

Check the diesel engines properly before buying, warm up the engine and try to accelerate with full throttle – the engine has to accelerate smoothly with enough power, without shuddering or jerking and without smoke from the exhaust!

Timing chain

All the engines are equipped with timing chain which can be usually worn just after 250 000 or 300 000 km, except the already mentioned petrol engines affected with the balance shaft horror story, the 4 cylinder diesel engine and the newer generation of V6 and V8 petrol engines which don’t have the check valves and new tensioners fitted. In all these cases the chain can be easily worn even at 150 000 km.

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Transmissions

-Most of the engines are equipped with the infamous 7 speed automatic gearbox. All you have to know about it is, that in cars made to 2008 it can have more often issues with the conductor plate-specifically a speed sensor on it fails more often, but sometimes also some of the solenoids can fail.

Next the torque converter failures are also not uncommon and some mechanical parts inside the gearbox can be more worn too. So definitely check for: harsh downshifts in lower gears, shuddering, or harsh shifting in general which are the symptoms of the gearbox issues.

On the other side from 2009 they improved this gearbox which means that with regular oil changes it will work for a long time.

-The older 5 speed automatic transmission is not that fast or up to date as the newer 7 speed but it’s more reliable. Although if the previous owner never changed the gearbox fluid then it can have also issues with more worn torque converter /sometimes even after 100 000 – 120 000 km/ But if the oil in it was changed regularly then it can withstand more than 200 000 km without issues.

As the last things I would add that the car has to ride smoothly at all speeds /even highway speeds!!/ without vibrations or strange whining eventually growling sounds.

To summarize things up:

• the best is to buy a car made from 2009
• I would avoid the hybrid models completely
• avoid cars with performance upgrades

+ it’s good to keep 5 000€ for the additional repairs, but if you are buying a V12 or one of the AMG versions then it’s good to keep twice that much money.

And as usual, if you have personal experience with this car or more information about it, then you can write it into comments!