Hello.

My 2012 S550 with 136K KM needs suspension work. Per a mechanic's paid diagnostic, I should replace all four struts, and air compressor, and valve block. Whether I go ahead with his recommendation, or start with one piece at a time, I need to find sources of reliable after-market parts. The dealership prices are $3100CAD for each strut (~$2300US each) plus installation extra. Compressor and valve block on top of it. I can't spend that kind of money on repairs.

1. Kindly suggest a good source and brand for air struts for W221 (2012 S550). I am in Canada but ordering from USA is not a problem at all. Please note that I live in an area where it gets pretty cold in winter so the temperature fluctuations between summer and winter months are wild. So please suggest a brand and source of solid repute. I have heard Arnott brand mentioned in many places. They sound like a leading brand. Any comments on experience with other brands that are a little cheaper, and do not have core charges?

2. Please also share your opinion and/or experience on removing air struts altogether, and just putting in after-market old fashioned spring struts. I know that drive would not be as luxurious and quite as offered by air struts, but it may be a cheaper and longer-term fix for an expensive problem. Also share if you are aware of a good brand/source for replacement/conversion SPRING struts.

Thank you!!!

 

Arnott

You usually don't need to replace the pump and valve block, especially at that mileage. Replace the struts and come back later.




Arnott's are usually an improvement over the conventional design in terms of durability because the bags are upgraded with Continental rubber and the struts are hand assembled and quality controlled although yeah it's still possible to get a lemon every now and then but you will know right away. Can't beat MB brand quality inspections. Via my shop I've personally seen 200k worth of combined mileage, I've also done 155mph on Arnotts hanging out there on a longer commute for a couple minutes no complaints.

In the states they pay $50 + shipping for each of the cores too so its a sweet $200 back for doing your maintenance. You can get even more money back signing up with a new credit card but yeah thats a different conversation.

 

Hello. Thanks for your comments!
Kindly share your opinion/experience with converting from air suspension to coil spring struts. Arnott sells a few kits for that. I am wondering if that seriously compromises the ride quality. How about saftey? Braking? Handling? etc.

Thanks.

 

You can also go to Rock Auto to see prices for Arnott as well as other manufacturers/brands. Parts Geek also has a big variety. Prices at both online stores are all over the place depending upon drive type and which wheel location.

 

I would go with the Arnott shocks, OEM valve block and compressor. You will also need the filter. Personally, I would only replace the parts that need replacing, especially if this is a DIY project. If you have an Xentry system or access to one, you will know which items need servicing/replacing.

 

don't do it? The car is actively levelled and adjusts it's dampening on the fly based on the road and speed. This would be impressive on a supercar, it's quadruplely impressive on a family car I eat and drink in at 100mph.

It won't have sway bars, hold level, stay composed through a corner, and I've seen compromised handling, braking, and even how it sits still will be at jeopardy. Not to mention the kits were usually by Strutmasters which isn't a great brand any day of the week. Arnott sells the conversions for a few cars I did one for a Range Rover that was EXCELLENT. If your only problems are Airmatic and not owning a Range Rover unironically. I would fix just whats broken.

To need the rear air sprints and front struts at the same time is rather unlikely. You can hear/see whats blown out, usually the boot and oil seepage will tell you visually, as well as hissing air audibly. The soapy water truck works if you have a leaking tophat/lines but thats less common in my experience.

So much is in the S550 that if you were to mess with it, it would be an affront to the experience. A lot of my benefit is simply existing in the car and feeling it level itself through turns, parking, starting it, bringing the height up when I'm driving through a gravel parking lot or driveway. A lot of this would not be a thing even if you were to find a suitable solution to save a grand on your best day. The system isn't very complicated when comparing to like an Audi R8's metal filled struts and few people have issues with the valve block and pump. The pump WILL die if you continue to drive and it's just trying to fill a leaking strut the entire time you're driving it but for the most part I've seen them go to 200k no problem, or in bad weather they start to eat it.

Also when buying an airmatic strut, it's a mount, spring perch, spring, bellow, bump stop all thats already been done for you with a new bushing at the bottom. You're getting a lot of value a lot of new parts and a lot of shiny stuff. Even the sticker is shiny and looks nice on the Arnott unit with Continental's logo for the air bladder which is now more durable. They get removed in less than an hour in actual time in each corner. I've seen people produce some nonsense about dropping the rear subframe for the air springs/rear strut but it's never been the case and I don't think Mercedes wants to build the car that way either.

 

I have a 2011 S550 4matic with 140,000 miles and was not having any problems but decided to replace all 4 struts, air compressor, valve block and front levelers before they went bad. I replaced them with Arnott units from Rock Auto. WHAT A MISTAKE!!! The 1st problem was that the right rear had a slow leak, which took a while to diagnose. Arnott high quality? What a joke - that's a 25% defect rate. After several weeks they replaced the strut. As for ride quality it's nowhere near what it used to be with the OEM parts. It rides stiffer and when I go over a drop in pavement I get a loud clunk that was never there before. I can now hear the compressor and could never hear the OEM compressor. Arnotts are supposed to be original ride quality but my S550 now rides like a common Cadillac.

I've read on other posts on this forum that you can find MB dealers in the States that will give you a discount on OEM parts. I wish I had checked that out but went with Arnotts as many recommended and have deeply regretted it.
As to replacing the Airmatic with springs just go out and buy a used Cadillac or Lincoln and you won't have to deal with the complexity of a Benz.

 

I've been following the GL forum here since I bought mine in 2007. For me, there are all too many instances of owners using the Arnott "warranty." You may get a "free" replacement, but the time and expense of installing isn't covered. It's not a super deal.

Understand that the front units are struts, meaning spring is combined with shock absorber. I wonder what Arnott's capability of manufacturing hydraulic shock absorbers is ...

To me, the only aftermarket units worth your trouble are Bilstein. There are real reasons why these are more expensive and Arnotts are cheap. It's not altruism or a greedy capitalist thing.

PS: I was there observing when my original fronts were replaced ... they were labeled Continental.

 

If you're using a qualified installer who buys them from a local vendor, the parts quality is guaranteed for 24 months/24k miles minimum. My shop uses a service called Worldpac, same-day delivery, if anything we're to happen I'd take care of it, it's really just another hour and I get a credit on the part installed back to my account and I get to keep my Amex points on the deal.

The Bilstein/Sachs/Monroe Spain units that are OEM do indeed have a higher quality control. That usually applies to most MB Genuine parts as a whole. I have a lot of data with Arnott, they're not perfect I've gotten one bad one in two years of installing about a dozen struts/springs/coilover kits but it's something that was picked up immediately before the install.