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R-Class (W251) 2006-Present: R320CDI, R350, R420CDI, R500


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Old 03-11-2010, 06:17 AM   #1
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2006 R350 4matic with rear suspension problem

Hi to everyone from a recent owner of a Europe-based CPO R350 4matic MY2006 but first registered in Aug 2009. The car has just 7.000 miles and I bought it directly off Mercedes Benz (not a dealer) who was in fact the previous owner (MB fleet).

The car save for a few creaks from the Panorama roof and various plastics looks and feels new. However, there seems to be a serious issue with the behaviour of the (full airmatic) suspension and specifically the rear, both sides, which delivers a very harsh and noisy ride over even small road imperfections (bumps, potholes etc). Since our roads are pretty bad I end up hearing a thunk almost every other minute on b-roards irrespective of airmatic setting( even in comfort mode)

Before purchasing the vehicle, I told the MB techs about the issue and they did a "thorough" check of the airmatic system. I told them about various horror stories with rear airmatic struts which I have read about in various forums. They insisted that the car makes the sound but "it's not from the struts". Star diagnostics shows no fault and there is no apparent leak or ride height related fault (so far). Drove other (older) cars, no such noise.

Pushing them to change the struts under the 2 year warranty is not working so far as they don't acknowledge that the noise is suspension/strut related. Also there is no specific TSB which covers the issue as far as I am converned. Now that I have bought the car, I have the option to let it get worse (can't get much worse...) before they act or pay for a couple of new struts myself (4.000 USD + labor over here). Since noise is coming equally from both sides I don't see what point there would be in changing just one.

Any thoughts about possible causes for the thunk noise or remedy thereof appreciated. Any way I can confirm that the strut is faulty besides the electronics diagnostics?

Many thanks in advance

Alex
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Last edited by alvas02; 03-11-2010 at 06:22 AM.
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Old 03-11-2010, 07:46 AM   #2
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I have full airmatic on my '06 R500 w/ 40k miles. It also thunks [thumps, thuds, etc.] over speed bumps when going about 5-10 mph. Although it seems to be counter intuitive, it is slightly harsher w/ the airmatic on comfort than it is w/ airmatic set on normal. Ever since I read your thread on the other forum, I have been thinking about this isssue and I am not confident that it is shock absorber related but rather just the suspension design along w/ tire noise. Every other W251 that I have driven does the same thing, regardless of mileage...interestingly, I don't get the thunk when traveling on rough roads at normal speed. I also had a full diagnostic done by the local dealer w/ no fault found. The warranty was almost out and they had the incentive to find something wrong, but still nothing...

Last edited by termite; 03-11-2010 at 07:48 AM. Reason: not enough coffee yet
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Old 03-11-2010, 08:12 AM   #3
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Hi termite and thanks for your input. My experience is also that normal mode can under certain speed/road conditions produce less thuds than comfort. Also concur that noises appear reduced at higher speeds but it could be that they are blended with other (nomral) sounds from the cabin/suspension as a result of a heavier & quicker impact.

Tire noise could be a factor, I have read that tire alignment can affect airmatic suspensions in general as would tire pressure. My alignment is slightly off and tires are stock 235/65/17 which are 4 years old now (be it with 7k miles). I am going to have both checked today.

Suspension design to me could also be a factor but not a major one as my car was a lot worse than two R's I drove on 3 different occasions.

I guess the key question to me remains whether struts/other suspension components have visual or mechanical tell-tell signs that are failed/failing...since electronics are not showing anything.
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Old 03-11-2010, 10:33 AM   #4
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What I forgot to add, which you may want to factor into the mix, is that the thud was perceptively worse w/ the snow tires on [Blizzaks at 34PSI front and back] which have a slightly higher load rating than the tires that the snows replaced. I haven't put the summer wheels and tires back on yet so I can't comment further on that but I suspect that part of the noise is indeed tire related...HTH
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Old 03-11-2010, 11:21 AM   #5
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I have noticed this thud too on my 2006 R500. However I think it is less noticeable when the vehicle is fully loaded with 6 passengers.

My warranty is over and the last visit to dealer to get repair for TSBs did not bring up this issue.
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Old 03-13-2010, 03:55 AM   #6
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Originally Posted by boochi101 View Post
I have noticed this thud too on my 2006 R500. However I think it is less noticeable when the vehicle is fully loaded with 6 passengers.

My warranty is over and the last visit to dealer to get repair for TSBs did not bring up this issue.
One more here. I also think w/o passengers it's worse.

And it's extremely bad if you raise the level
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Old 03-14-2010, 01:42 PM   #7
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Interesting that other owners have the same experience, I bet many more are out there. I also notice the same suspension behaviour i.e. less thuds with more loading and also worse at the raised suspension level.

To other posters who report the same problem: Have you replaced air struts, or indeed made any other attempts to resolve the issue? I am asking because I am about to start a major campaign to get MB to replace the struts (I think both) under warranty, if not succesfull I will just pay myself for the parts myself or sell the vehicle. This type of ride quality is unacceptable and clearly not "normal"
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Old 03-14-2010, 02:14 PM   #8
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When raised, the ride is very rough, but i expect that that is really the way it is designed...my front struts were replaced under warranty along w/ the sway bar end links at just under 40k miles but it was done by the prior owner and i don't know why they were replaced.
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Old 04-15-2010, 05:38 AM   #9
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An update on this saga: I had the shocks rated/measured yesterday at an independent suspension specialist. The results were v. interesting: Front Shocks 100% rating; rear left 73%, rear right 67%. I was present during the test.

There was a terrible vibration/thunk noise coming from the rear suspension while the car was being measured on the suspension test bench. No such issue when testing the front. Also they lifted the car and noted that two of the rear bushings (control arm) where worn out possibly due to the reduced rear shocks' performance.

It's obvious that this kind of drop in the shock's performance with just 7.500 miles on the clock is not justified. It is still possible that there is a control unit or other electronics issue at fault but the primary suspects are now the air shocks themselves. Will now pressure MB to replace both under warranty.

a.
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Old 04-15-2010, 09:35 AM   #10
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I believe also that for 2006 there was a design flaw in some of the rear shock (or strut or whatever you call it) with the top plate separating from the shock mounts in many cases and the entire unit needing replacement - one of mine was leaking and replaced under warranty. NO I don't have Airmatic. Just load levelling in the back.
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Old 05-07-2010, 03:48 AM   #11
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Just an update on the issue: I had both rear shocks changed under warranty (MB look a lot of convincing to accept) and the thud is gone! Ride is smooth and I am well pleased with the outcome.

To previous posters of similar issues: Have your car's suspension performance measured (% rating on shocks). This is not normal and can be fixed. This is not how an R-Class is supposed to drive. Granted that there could be other reasons for such noises but I would start with the shocks.
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Old 05-10-2010, 07:43 PM   #12
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Originally Posted by alvas02 View Post
Just an update on the issue: I had both rear shocks changed under warranty (MB look a lot of convincing to accept) and the thud is gone! Ride is smooth and I am well pleased with the outcome.

To previous posters of similar issues: Have your car's suspension performance measured (% rating on shocks). This is not normal and can be fixed. This is not how an R-Class is supposed to drive. Granted that there could be other reasons for such noises but I would start with the shocks.
So they just replaced the shock, and not the suspension "airbag"? Do you know how much was the shock? I think I have then the same issue, not measured the performance yet. Just wondering how much would it be to replace them...
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Old 05-11-2010, 03:30 AM   #13
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So they just replaced the shock, and not the suspension "airbag"? Do you know how much was the shock? I think I have then the same issue, not measured the performance yet. Just wondering how much would it be to replace them...
Yes, they only changed the shocks; at the rear at least they are independent of the "airbag" assembly. I don't know the exact price as they were replaced under warranty. I can tell you that they theoretically charged 1,7 manhours for the job.

From online sources in the US (I am in Europe) you can probably buy the shocks for something like $600 a piece.
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Old 10-23-2010, 03:55 PM   #14
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ello,
I just bought a 2007 R350, w/57K miles, w/o air suspension and shocks only (but I could see air bellows, what are they?) and I am experiencing a very rough ride in the back. Every time I hit a bump (without passengers/no load in the back). I hear a thud from rear shocks as if it is bottoming down and I am very upset with the performance disappointed and thinking of returning the vehicle.

For sure, I don't have the air suspension, in which case, by changing the rear two shocks can the bottoming down problem be rectified? Any one out there had a similar problem? and how to get around it?.

Pls help me with real solution/suggestions.

Thanks
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Old 10-25-2010, 08:28 AM   #15
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ello,

For sure, I don't have the air suspension, in which case, by changing the rear two shocks can the bottoming down problem be rectified?
In fact, you have air suspension in the rear. All Rs have auto leveling in the rear suspension even if not having real time damping system (which is the "full" air suspension including air suspension front and rear + adjustment for sport/comfort/normal damping), and auto leveling is done with air suspension in R model (and other like E wagons, etc.).

Not sure of cure though, it might be the air suspension or the shocks. I have similar issue, but not seeing it as a major problem right now, as it mostly works just fine.
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Old 10-25-2010, 06:24 PM   #16
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Thank you Veppe,

I saw air bags on either side of the rear wheel suspension when lfted on the ramp but the mechaic does not call it a air suspension. I think the air bags are nor inflated and the vehicle sits low on the rear. I checked the air suspension fuses 2 x 40 in theenine compartment and they are intact.Perhaps the auto level adjuting system has leak.

It is a disappointment to have bad ride like this.

Thanks again
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Old 10-25-2010, 06:24 PM
 
 
 
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2006, 350, air, airmatic, bumps, end, front, mercedes, noise, problems, r350, rear, ride, strut, struts, suspension, tire



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