Mercedes S-class (W221) 2006-2013

AIRMATIC

-This is a regular self leveling air suspension which is obviously comfortable, but you can adjust it from comfort to a bit stiffer sport mode as well, and you can raise the car a little with a button on the dash.

“In the before facelift cars you can put the suspension from comfort to sport mode only with the button on the center console, which means that in this case the sport mode of the suspension will be activated only with the sport mode of the gearbox at the same time. On the other side in the newer facelifted cars you can adjust the suspension to sport mode by pushing the sport button on the dash which means that in these newer cars you can adjust the suspension and the gearbox characteristics separately”

It’s all great and awesome, but there are the well-known air suspension parts which will sooner or later break, so: mainly the air compressor can more often wear out, the air struts can start to leak anytime basically-although still mostly on the before facelift cars, and rarely one of the air pipes can crack a little and leak. All of this means that you should definitely keep extra money to replace at least half of these parts. However replacing the air struts or the air compressor is actually not hard at all, and while the genuine parts are obviously expensive, there are also refurbished or new aftermarket struts and air compressors available for a much lower price + there are the very cheap air compressor repair kits available too.

Before buying:

• It’s good to test the air suspension by at least raising and lowering the car a couple of times
• Make sure the car is raising at a noticeable speed and the compressor is not very noisy! (the air compressor is located behind the front fender on the right side)
• Check if the car is standing in level
• Inspect the struts visually for damage
• And keep in mind that the suspension should not lower even after a week of sitting!

ABC

-But let’s move on to the ABC active hydraulic suspension which is also comfortable, adjustable and self leveling. To top of that, compared to the airmatic it significantly reduces the body roll in all situations. So while the adaptive air suspension slowly adapts to the various situations, the active hydraulic suspension very quickly actively adapts to the situations-it actually adapts 5 times/second they say!

And again, it’s all great and awesome but the maintenance and repair costs of this suspension are higher than in cars with the conventional airmatic setup. Although I have to add that this ABC suspension is more reliable than in the previous generation of this S class, and it can actually withstand more than 200 000 km without issues – but this of course doesn’t mean that there are no weak points.

Instead of air, this ABC suspension uses hydraulic fluid which is under high pressure. The fluid is distributed by numerous lines thru the valve blocks into the accumulators and shocks. The pressure is maintained by a main pump which is mounted on the front of the engine.

And this pump can be faulty. So if you hear various whining, howling or grumbling noises (turbine like, turbocharger like sounds) from the pump and you feel a vibration in the interior and especially in the steering wheel at idle-up to approximately 2000 RPM, then most probably the pulsation dampener mounted on this pump is faulty. The pulsation dampener is there to even out the vibrations in the fluid from the pump, so that’s why when it fails you get the already mentioned symptoms. The good thing is, that this part itself is not that expensive, however in cars equipped with the V8 engines there is very little space around the pulsation dampener, so it’s harder to replace it, which means that you have to: release the engine mount-remove the whole pump-and just then replace the pulsation dampener itself. On the other side the paradox is that in cars with the V12 engines the pulsation damper can be replaced easily without removing the whole pump!

Interestingly, sometimes the expensive pump itself can be worn as well. But you have to remember that not only the ABC pump but also the power steering pump is combined in this single unit, so it is complex and expensive. However you can have it refurbished for a much lower price, or you can buy a used pump if you like to gamble.

Then there are the lines which can crack/burst and leak, and not only because of the age or faith, but also because of the road salt which will cause corrosion on them. So before buying check not only for the already mentioned pump noises but also for leaks from these pipes, and especially check the lines in in front of the engine since one of them can burst more often and dump all the fluid out.

“Keep in mind that if one of the oil line bursts and your pump will run on low or no fluid at all – even for a very short time, then there is a very high chance that the pump gets permanently damaged and it starts to make the already mentioned noises!”

On the other side not only the pipes, but also the shock absorbers themselves can start to leak. However I have to add that this is not like extremely common and mostly still just the before facelift cars are affected because of the age. But if the shock is just misting oil then there is no need to panic, just check the fluid level regularly (the misting can actually remain the same for a couple of years without getting worse, so you can leave it like this with no worries – just occasionally check it if it’s not getting worse). However if it starts to visibly drip oil and you can see that the oil level is slowly decreasing then you should replace the shock in the near future! Nevertheless, be mentally prepared that one brand new ABC shock absorber costs approximately the same as the new pump, although again because of the high price there are also remanufactured shocks available which are cheaper. + if you have like really bad quality roads in your country then be prepared that the strut in these shocks can break-there are already some cases of this (yes there is a regular strut in these special struts, and if the strut breaks then the car will handle like garbage, obviously)

stiff ABC suspension on before facelift cars can be caused by faulty acceleration sensors more info here

To minimize issues with the various components of this complex suspension and to extend its lifetime – you should definitely replace the hydraulic fluid and filter in this system every 4 years or 60 000 km and check the fluid level regularly. By the way if you want to replace the ABC filter then keep in mind that you can’t order it for the w221 separately. However the filter is identical with the W220 models which can be actually ordered separately, so just order the filter for the W220 models and put it in your W221.

how to replace ABC fluid video , the tool to flush the system