Mercedes R-class (W251) 2005-2017

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The Mercedes R-class is a spacious, practical, and comfortable family car. It has unusual design to say at least, and it shares some of the components, engines and more or less also the reliability with the Mercedes M-class from that time.

The interior is spacious enough even in the standard version, but if you want more trunk space and if you want to use the third row seats more often than it’s better to choose the long wheelbase model.

There are basically no issues with the interior which is good news. So it has plenty of storage areas, comfortable seats even in the back and you can find mostly well equipped cars with plenty of features + the interior is usually not worn even in cars with 400 000 km or more. Only the navigation system is that older unit, so you can’t expect a fancy up to date touchscreen multimedia system in these cars.

Possible problems

With the proper maintenance this Mercedes can reach 300 000 or 400 000 km without major problems. But generally speaking it really is better to avoid the early production cars, mainly because the models made to 2007 or early 2008 do have more often various-usually minor electronic and some other issues:

The tail lights can stop working even if the bulbs are fine. In this case the issue is usually with the tail light wiring harness which is not very expensive to fix, since you can buy a genuine tail light harness repair kit, and the cars from 2008 do have updated tail light wiring harness.

-Then the rear electronic tailgate can cause some issues. It’s either not working at all, or it just can’t open or close properly. Sometimes the latch is faulty, sometimes the hydraulic lifter pump, and sometimes the issue is in the control module or in the wiring harness. Interestingly, occasionally even the dealer can’t diagnose what exactly is wrong with it.

Battery draining can also occur on these early cars.

“Most of these minor problems were already fixed under warranty or by the owners, but of course some of these cars can still suffer from these issues.”

On the other side there can be a more serious problem with the front differential and with the transfer case, again mostly in cars made to early 2008. But some say that it affects the newer cars as well although not that often as the older models.

-So the front differential and the transfer case can fail simply because of worn bearings. The good thing is, that you can change only these faulty bearings so it’s not necessary to buy the complete part-although you still have to disassemble the front differential and the transfer case to change these bearings. The usual symptoms of this issue are strange whining, growling, howling or grinding/clicking noises from the front while driving. You can hear these strange sounds usually while letting off the gas or coasting + check for strange vibration from 1 800 to 2 000 RPM.

“Changing the fluids in the differentials and transfer case after 90 000 km is definitely a good idea.”

Because of these possible problems, I would simply not recommend buying an early car. Of course it can be good, it can work well for a long time-mainly if most of these things were already fixed, but there still is a bigger chance that it will have some kind of a design flaw.

It’s very important to check for water leaks in the interior, mainly under the passenger seat, since the battery and some of the control modules are located in this area. The water can easily leak in there thru the cabin air filter which is located under the windscreen on the passenger side. There is a plastic air inlet which fills up with water-if the water drains under this inlet are clogged of course. And the water simply leak thru the air filters into the interior, to the battery and you can say hello to the various electronic gremlins. And that’s how the magic happens. On the other side, you can easily remove this air inlet so occasionally just check and clean this area.

It’s also good to check the trunk, especially the spare tire area for water since the tail lamp seals can fail and let the water inside.

And of course I have to mention the sunroof water drains which can be again clogged, so if your car is equipped with the sunroof then it’s good to occasionally clean them.

Suspension

There are cars with:

standard suspension

the air suspension only on the rear axle

and cars with the optional Airmatic adaptive air suspension in all 4 corners

Obviously if you want a reliable solution then try to find a car with the regular suspension, because the air suspension is in this case not the most reliable. The lifetime of the genuine Mercedes air springs is usually somewhere near 96 000 km / 60 000 mi or 112 000 km / 70 000 mi, so be prepared to change them if they start to leak. (There is no need to buy the very expensive parts from the dealer, because you can buy them from a well known aftermarket manufacturer for a much better price)

Petrol engines

From the petrol engines the most reliable is the older 5.0l V8 with the M113 engine code which was available only in the early production cars-which is little bit a paradox. On the other side, the other engines are not that bad either although there are 2 possible problems which can occur on these newer units.

-The first is the well-known balance shaft sprocket failure which can occur mainly in cars made to 2007 but also on some of the early 2008 models. Mostly the V6 engines are affected by this, but rarely there are cases of some V8 engines with worn sprockets. Because of the already mentioned worn balance shaft sprockets the timing chain can fail which can destroy the engine. All in all, it’s simply better to avoid the cars made to mid-2008 unless the previous owner replaced the sprocket and the timing chain since it can cost up to 4 000€ to fix this preventively.

-The next possible problem is related to the intake manifold. Basically a plastic arm on the outside can break or sometimes the plastic flaps inside the intake manifold can break as well-causing misfires, loss of power and eventually an illuminated check engine light. You can fix the broken outside plastic arm by removing and cleaning the intake manifold and replacing only the broken arm with an improved metallic one, or you can just buy a new complete intake manifold which is in a lot of cases a better and faster solution, since after replacing the outside arm only, the inside plastic flaps can still break.

By the way there is also the rare R63 model which is simply madness on wheels, but there is a known issue with these AMG engines. Because of the faulty head bolt design the head bolts can fail and this usually causes head gasket failure which is in this case a very expensive issue. So if you are buying one of these and you found one, then you should preventively change these head bolts. You can find more information about this head bolt issue in my Mercedes E55 / E63 used car review.

Diesel engines

The diesel engines can have luckily only usual problems, so just use them mainly on longer journeys, use high quality fuel and change all the fluids and filters in time.

All the engines are equipped with timing chain which can be worn after 250 000 – 300 000 km, so I would be prepared to change it after this mileage point. (But of course some of those engines with the balance shaft sprocket failure can have issues with the timing chain much earlier)

This Mercedes can be equipped with the 7 speed automatic gearbox only. Definitely check it properly before buying and change the oil in it, because there are numerous cases when the conductor plate failed. This is a bad situation to be in since the whole transmission is really expensive. But there is no need to replace the whole transmission because the conductor plate itself can be repaired for around 250 €, but in this case it’s good to change the transmission oil with the filter as well and that is + approx. 350 € at an independedent mechanic.

It’s also good to check the power steering fluid level. You can access the power steering fluid reservoir by removing the plastic engine cover. Most of the time only the reservoir gasket is leaking, but it’s good to change the whole reservoir as well because it has a filter in it-and of course in this case it’s good to change the power steering fluid too. Keep in mind, that the lack of power steering fluid can easily destroy the power steering pump which is expensive.

To summarize things up: it’s better to buy a properly maintained car made in late 2008 or better made from 2009, buy only a car with maintenance history, find a good independent specialist, change all the fluids in time and keep at least 3 000 € for the possible repairs.

As usual check the car properly before buying, and if you have personal experience with this car or more information about it then you can write it into comments!

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