S-Class (W221) 2007-2013: S 320 CDI, S 350, S 450, S 500, S 550, S 420 CDI, S 600

Shock Absorption Completely Gone After New Front Air Struts

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Old 07-16-2024, 07:33 PM
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Shock Absorption Completely Gone After New Front Air Struts

Hi.

The front air struts on my 2012 S550 4Matic (146K KM) started to leak, so I had to replace those. I found a new pair at AutoShack at very attractive (cheap!) price. See Front Air Struts Assembly Set of 2 Driver and Passenger Side | KAS238M30FPR | AutoShack | AutoShack.ca

The new struts appeared to work OK. Get filled with air, and hold air (I know this because when the car is turned off and locked, the air leaves struts in an audible immediate hiss--like a pressure release noise you hear from buses, etc.), and get refilled up when car is started. Plus, no more sagging car so I know that the "air" part of these struts is working fine. However... the shock absorption appears to have completely gone. Even the small bumps or cracks in the road, which we won't even know are there when driving over them in mainstream vehicles with regular spring struts, cause a bang/thud and bump in S550 ever since we put the new air struts bought from AutoShack. And if the crack is slightly larger or the bump in road is a little more pronounced, the thud noise it creates when the S550 goes over it, makes we worried that it may cut the tire or damage the wheel assembly. That's how jolting and rough its reaction is to the unevenness in the road.

Does it sound like that I was sold a total dud of a strut? That is, it only holds air to keep the car raised, but no shock absorption whatsoever. ??? Or, by any chance, could these symptoms be due to new struts having been installed wrong? Although I don't think they were installed wrong because I watched them install it, and there are no error codes or erratic driving etc. (car drives and handles just fine!). But I still wanted to ask for experts' opinion because my next course of action is to purchase another set of front air struts from a reputable source (like Rock Auto--built by Arnott, etc.). And I don't want to do that if it I am going to end up with same harsh thud noises ride again if the symptoms I am describing are due to improper installation.

While we are at it, is Rebuild Master Tech a good place to have the W221's Air Struts rebuilt?

Please advise.

Thanks!!!!

Last edited by cad1857; 07-16-2024 at 07:40 PM.
Old 07-16-2024, 08:16 PM
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Originally Posted by cad1857
Hi.

The front air struts on my 2012 S550 4Matic (146K KM) started to leak, so I had to replace those. I found a new pair at AutoShack at very attractive (cheap!) price. See Front Air Struts Assembly Set of 2 Driver and Passenger Side | KAS238M30FPR | AutoShack | AutoShack.ca

The new struts appeared to work OK. Get filled with air, and hold air (I know this because when the car is turned off and locked, the air leaves struts in an audible immediate hiss--like a pressure release noise you hear from buses, etc.), and get refilled up when car is started. Plus, no more sagging car so I know that the "air" part of these struts is working fine. However... the shock absorption appears to have completely gone. Even the small bumps or cracks in the road, which we won't even know are there when driving over them in mainstream vehicles with regular spring struts, cause a bang/thud and bump in S550 ever since we put the new air struts bought from AutoShack. And if the crack is slightly larger or the bump in road is a little more pronounced, the thud noise it creates when the S550 goes over it, makes we worried that it may cut the tire or damage the wheel assembly. That's how jolting and rough its reaction is to the unevenness in the road.

Does it sound like that I was sold a total dud of a strut? That is, it only holds air to keep the car raised, but no shock absorption whatsoever. ??? Or, by any chance, could these symptoms be due to new struts having been installed wrong? Although I don't think they were installed wrong because I watched them install it, and there are no error codes or erratic driving etc. (car drives and handles just fine!). But I still wanted to ask for experts' opinion because my next course of action is to purchase another set of front air struts from a reputable source (like Rock Auto--built by Arnott, etc.). And I don't want to do that if it I am going to end up with same harsh thud noises ride again if the symptoms I am describing are due to improper installation.

While we are at it, is Rebuild Master Tech a good place to have the W221's Air Struts rebuilt?

Please advise.

Thanks!!!!
It sounds to me the new struts shock absorption works. Shocks make ride rough compared to no or weak absorption.

Perhaps you got used to driving your car with badly worn shocks that gave you softer ride?
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Old 07-16-2024, 10:58 PM
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Originally Posted by Arrie
It sounds to me the new struts shock absorption works. Shocks make ride rough compared to no or weak absorption.

Perhaps you got used to driving your car with badly worn shocks that gave you softer ride?
Hmmm....that's an angle I had not viewed from before. So, there may not be any problem then?
Old 07-17-2024, 03:58 AM
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modern cars ride like **** - its a two part idea

1) so that brain dead playstation generation drivers and women can attempt to navigate corners 3 times faster than physics allows
2) to ensure the wheels crack and your money keeps the criminals ruining german car companies in helicopter rides to castles hidden in the Austrian mountains - safe from the masses

I wounder if you have the correct dampers for the car - some later ones auto tune constantly, others move from horrible wallow to rattle the car via a button and even cheaper ones get nothing
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Old 07-17-2024, 06:31 AM
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Originally Posted by cad1857
Hmmm....that's an angle I had not viewed from before. So, there may not be any problem then?
Yes, may be just fine.

If you press a corner of your car down and let it bounce back, does the movement stop after just one cycle or does it give several before it stop moving? Several means shock is not working.

These cars ride rough, much rougher that you would assume a luxury car like this should ride in my opinion. I think the reason is the car is heavy and with that it is made to run million MPH on the German Autobahn so very sporty stiff suspension is a must have.

Before my first MB I had an Audi Q7. That was a nice SUV but its suspension was so stiff it beat my back to pieces. It felt like it had no sprigs at all other than what the tires gave you. I think it was due to the same high speed reason.
.
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Old 07-17-2024, 12:04 PM
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It is your cheap shocks. S-class should be floating and is the best ridding Mercedes.
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Old 07-17-2024, 06:58 PM
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Originally Posted by doni01
It is your cheap shocks. S-class should be floating and is the best ridding Mercedes.
Thanks for your note.
I am totally confused now. A few replies have me believe that the rough ride and thuds and feeling like there is no shock absorption is what's is supposed to be like. And then there is your comment, which validates what I am expecting. I remember the car's ride when the original struts were on. It was quiet, and like the best ride ever.

Time to buy better shocks, then?
Suggestion.....? Arnott? Have the originals rebuilt from Rebuild Master Tech?

Thanks


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Old 07-17-2024, 06:59 PM
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Originally Posted by Arrie
Yes, may be just fine.

If you press a corner of your car down and let it bounce back, does the movement stop after just one cycle or does it give several before it stop moving? Several means shock is not working.

These cars ride rough, much rougher that you would assume a luxury car like this should ride in my opinion. I think the reason is the car is heavy and with that it is made to run million MPH on the German Autobahn so very sporty stiff suspension is a must have.

Before my first MB I had an Audi Q7. That was a nice SUV but its suspension was so stiff it beat my back to pieces. It felt like it had no sprigs at all other than what the tires gave you. I think it was due to the same high speed reason.
.
Your comments make sense but don't agree with how I remember the ride to be when original struts were on. It was quiet and comfortable yet firm and in-command ride.
I am confused now....
Old 07-17-2024, 11:39 PM
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Originally Posted by cad1857
Your comments make sense but don't agree with how I remember the ride to be when original struts were on. It was quiet and comfortable yet firm and in-command ride.
I am confused now....
Don't be confused. Your car on the originals was riding the way it's supposed to. With a background in automotive service and repair i can tell you buying cheap aftermarket is always a big gamble. Out of 10 struts 1 or 2 might be good and last a while. The original bilsteins are quality built units and are made to last long time while providing the best ride. Arnotts WERE absolutely phenomenal but in recent years the qc has been hit and miss. Comparing to off brand Chinese units i would rather use arnott if buying originals/bilsteins are not an option.
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Old 07-18-2024, 10:29 AM
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Originally Posted by cad1857
Thanks for your note.
I am totally confused now. A few replies have me believe that the rough ride and thuds and feeling like there is no shock absorption is what's is supposed to be like. And then there is your comment, which validates what I am expecting. I remember the car's ride when the original struts were on. It was quiet, and like the best ride ever.

Time to buy better shocks, then?
Suggestion.....? Arnott? Have the originals rebuilt from Rebuild Master Tech?

Thanks
I am not a fan of Arnott's since their quality control has gone to crap. Best would be Bilsteins but those are pricey so second best will be Remans from the Mercedes Dealer. Shop online to get the best deal.

Don't know what other people's car are riding like BUT the S-Class should be riding like an air cloud. That's the whole idea behind the air airmatic. If they wanted a stiff ride or a tough ride they would have stuck with the traditional suspension. Usually when the car rides rough as it's missing the shocks just like you describe it, it means that there is an issue with the airmatic and the car has gone into a Safe Mode. Do e search on Airmatic Stiff Ride on the forum and there will be all your answers 👍
Old 07-18-2024, 10:38 AM
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I'd have to drive it to compare. Maybe you got duds. Who knows.
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Old 07-18-2024, 01:37 PM
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Originally Posted by doni01
I am not a fan of Arnott's since their quality control has gone to crap. Best would be Bilsteins but those are pricey so second best will be Remans from the Mercedes Dealer. Shop online to get the best deal.

Don't know what other people's car are riding like BUT the S-Class should be riding like an air cloud. That's the whole idea behind the air airmatic. If they wanted a stiff ride or a tough ride they would have stuck with the traditional suspension. Usually when the car rides rough as it's missing the shocks just like you describe it, it means that there is an issue with the airmatic and the car has gone into a Safe Mode. Do e search on Airmatic Stiff Ride on the forum and there will be all your answers 👍
A spring is a spring no matter how it is made. Air spring does not make it any softer than steel spring if it is made to the same spring constant.

The benefit of the air spring is the much less weight, which lowers the mass that moves with wheel and so brings better response for the wheel to stay in contact with road surface.

Air spring also allows changing the ride height that our cars could do with speed, but I’m not sure if S-class does it as the change in height changes the toe on front wheels so perhaps the S-class is programmed to maintain the set drive height with all speeds. E-class with AirMatic lowers the height with faster speeds that it can do with the front suspension it has.

But again, if you make the air spring to the same spring ration as steel spring it is just as hard as a spring.
Old 07-20-2024, 09:51 AM
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Originally Posted by Arrie
A spring is a spring no matter how it is made. Air spring does not make it any softer than steel spring if it is made to the same spring rate.
Fixed that for you. You are wrong about a “spring being a spring.”

With air ride the compressed air merely holds the car up. More compressed air means the car will be further from the ground. Compressed air lacks the ‘memory’ of steel springs that will have wheels bouncing at multiple frequencies at once where there is no dampener to control the steel spring. With air ride the ‘spring rate’ is done via the size of the bag. A bag 6” round at the mounting point requires less air pressure than a 4” bag.

Dampeners aka shock absorbers are where the magic happens. Today there is much black magic cooked into them.

OP get OEM or Bilstein shocks to replace the junk currently installed.

If suspension arms are not fresh this is your opportunity to replace them as well.

Your car did not thump or thud over anything when new unless it came with run flat tires which any sane individual swaps out for a conventional tire.

Last edited by JohnLane; 07-20-2024 at 09:55 AM.
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Old 07-21-2024, 07:25 PM
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Originally Posted by JohnLane
Fixed that for you. You are wrong about a “spring being a spring.”

With air ride the compressed air merely holds the car up. More compressed air means the car will be further from the ground. Compressed air lacks the ‘memory’ of steel springs that will have wheels bouncing at multiple frequencies at once where there is no dampener to control the steel spring. With air ride the ‘spring rate’ is done via the size of the bag. A bag 6” round at the mounting point requires less air pressure than a 4” bag.

Dampeners aka shock absorbers are where the magic happens. Today there is much black magic cooked into them.

OP get OEM or Bilstein shocks to replace the junk currently installed.

If suspension arms are not fresh this is your opportunity to replace them as well.

Your car did not thump or thud over anything when new unless it came with run flat tires which any sane individual swaps out for a conventional tire.
You obviously are not a mechanical engineer and do not understand how springs work so I leave it with that. This forum is not a place to start educating someone for this from zero.
Old 07-21-2024, 08:02 PM
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Originally Posted by Arrie
You obviously are not a mechanical engineer and do not understand how springs work so I leave it with that. This forum is not a place to start educating someone for this from zero.
Duly noted. I won’t waste time on you.

Welcome to my ignore list. Population: One.

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Old 07-22-2024, 11:40 AM
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cad,

Did you change the struts yourself? If so, did you check the lower ball joints?

If the lower control arms ball joints are worn you will get a "clunk" when you drive over bumps or "cracks" on road. It is usually the rearward control arms that develop the wear as these are the arms that carry the weight of the car in front but of course the forward arm joint can also wear with time.

Checking for the joints is not as easy as it is with "normal" suspension. This MB suspension with the two lower control arms puts a big force in the joints that prevents checking for joint wear just by jacking the wheel up and trying to wiggle the wheel by hand. There is too much force in the joints to make them move by hand.

To check the joints, you need to disconnect the sway bar from the wheel hub and then disconnect the upper wish bone arm.

When I replaced my front struts (Arnott struts from FCP Euro) I had a bottle jack under the rearward control arm to jack the hub up for disconnecting the upper wish bone. When I then lowered the bottle jack the hub turned toward rear, i.e., the driver side turned clockwise and passenger side counterclockwise. With this turn the force from the ball joints disappears and you can then move the hub around by hand and see if there is wear in the joints.

Without taking the wishbone arm loose it is not possible to check joints by hand what is they would do in any garage you take your car to, including MB. You would get "good health" for the joints from any place, but you will hear the clunk/thumb driving over the imperfections on the road. You would get problem note if they see the protective rubber boot broken but nothing else.

So, my message to you is that before you go throw money for new struts check the lower control arms ball joints for wear. It does not hurt checking the upper wishbone joint too. There is also rubber at each control arm mounts that can wear/fail but when these go you would see other issues like car could not keep direction. For checking these rubbers other than looking at them (difficult to see) you need to relieve the force from the arms just the same as for the ball joints so this would be done at the same time as checking the ball joints. Throwing new struts in the car will not eliminate the noise if it is coming from the suspension parts I explain above.

What comes to using other than Billstein struts, I have some experience on these too. I have a 2010 E550 with the Airmatic and my rear springs first developed a leak and after fixing this with Arnott springs (work perfectly) my front developed a leak. At that time there were no Arnott front struts available for the E-class so I had to go with the expensive OEM struts that I bought from FCP Euro.

These struts were made by the same company in Spain who makes them for Mercedes. Ride quality was the same very harsh for a car you would expect to be a bit softer, it is just like it was with the original struts in the car. E-class also has a very distinctive problem when you drive over a "hole" or something that allows the wheel drop to its limit. It makes a huge bang and MB has no solution for this. This noise sounds like something will break...

For my S-class I use Arnott struts. I replaced them in the front after the driver side developed a leak. Had bad luck with one of them as out the box it leaked. I got a replacement very fast before I even returned the leaking one and all was fine. No difference in ride quality. The car was very stiff going over bumps on road just the same it was with the original struts that came with the car.

Now, there are several companies selling these remanufactured struts and all of them may not be replacing parts in the struts other than fixing the leak so there may be big differences, but I can say Arnott struts and air springs have served my cars well. I understand they also fix the internals of the struts, not just the leaking air bag.

Old 07-22-2024, 01:39 PM
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Originally Posted by Arrie
cad,

Did you change the struts yourself? If so, did you check the lower ball joints?
.
Ball joints have nothing to do with the car riding stiff! Also his car riding stiff started right after he change his oem shocks to chinese junk shocks. Best thing he can do is check the car via DAS and see of any codes related to the suspension. If not, the answer is the junk/cheap shocks that he installed.
Old 07-22-2024, 04:43 PM
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Originally Posted by doni01
Ball joints have nothing to do with the car riding stiff! Also his car riding stiff started right after he change his oem shocks to chinese junk shocks. Best thing he can do is check the car via DAS and see of any codes related to the suspension. If not, the answer is the junk/cheap shocks that he installed.
You should read OP’s original post again where he talks about bang/thud noise.
Old 07-22-2024, 09:22 PM
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Originally Posted by Arrie
You should read OP’s original post again where he talks about bang/thud noise.
The bang/thud noise is coming from shocks hitting hard and I had the same issue on my W220. If you do a search it will pop up. The car hit hard every pothole as it was on Sport highest setting. Therefore lower control arm had none to do with it. In my case one of my shocks had failed internaly and the car had gone into a Safe Mode which translates Stiff Suspension. Once shock was replaced and the alignment done, it rode like a dream once again.
Old 07-22-2024, 11:44 PM
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Originally Posted by doni01
The bang/thud noise is coming from shocks hitting hard and I had the same issue on my W220. If you do a search it will pop up. The car hit hard every pothole as it was on Sport highest setting. Therefore lower control arm had none to do with it. In my case one of my shocks had failed internaly and the car had gone into a Safe Mode which translates Stiff Suspension. Once shock was replaced and the alignment done, it rode like a dream once again.
I also experienced both types of problem and it is very difficult if not impossible to tell which one is the problem, the internals of the shock or worn-out ball joints. I'm trying to give info for the OP what to look at first before spending top dollars on new struts. It is the worst feeling to realize the struts were not the problem and the worn-out ball joints were especially when someone warned about it first. Perhaps I should not have told my opinion, but as I experienced it with two of these W221 cars I just thought to let OP know.

If he is hands-on person at all he can check the ball joints, but it takes a little work as I have explained.
Old 07-26-2024, 11:57 PM
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If the nitrogen has leaked from the bottom of the shock to the top you'll get banging when the wheel goes up and clunking when the wheel goes down as the top parts fluid is contaminated with gas. The car will bounce more than once over bumps.
You can just fit dubious new air bags to your old shocks.

Last edited by Hullow; 07-27-2024 at 12:04 AM.
Old 07-28-2024, 12:29 PM
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Originally Posted by Hullow
If the nitrogen has leaked from the bottom of the shock to the top you'll get banging when the wheel goes up and clunking when the wheel goes down as the top parts fluid is contaminated with gas. The car will bounce more than once over bumps.
You can just fit dubious new air bags to your old shocks.
Obvious solution being to replace the strut assembly with a quality replacement. Bilstein or MB are my pick. Your car your choice.
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