Right nearside thumping on bumps

duncanh

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I have had a thump on bumps/potholes for the last 3 years on my s203 (2002). It sounds like suspension (I have tried just about everything else). With no tools/spare wheel, load covers and with the tailgate open it still rattles. An indie told me it was a broken spring. I have taken the spring out and can guarantee that it is not broken. It has now passed its last 3 MOT tests like this. No one can find any play anywhere around the rear suspension. The exhaust is not hitting, there appears to be no play in the rear subframe bushes. It is less apparent when the car is loaded (or maybe that is imagination).

The one thing that no one has mentioned is the self levelling spheres. I have one of the few W203s with SLS. Is this the sort of thing that could happen with a worn sphere? If it is the sphere, would it not show up at MOT time? There is no sign of any sagging at the rear.

I don't think that replacement spheres are available other than from MB.

Is there a way that the operation of a sphere can be tested?

The car has done 303K miles, the only bits of the rear suspension that have been changed are the ARB bushes and droplinks. The diff damping bushes have also been changed.

It would be nice to get rid of this noise. It is a dull thump.

I would welcome any other suggested possibilities.
 

Steve@Avantgarde

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Im wondering if its a shock absorber Duncan. I did a W210 with 280k on it for roughly the same fault. I changed the spheres first and it made no difference so I swapped the shocks and it cured it.
 
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duncanh

duncanh

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Steve,

I excluded that previously from my thinking because I had been informed that the only likely failure of the rear hydraulic shocks was caused by fluid leakage. Mine are bone dry. However if you have seen it on a W210 it may be the answer. I assume the SLS system is similar on both models?

Why is it not picked up during the MOT? The back end fairly bangs on a bumpy road. Surely the MOT testing systems that shake the suspension would make it bump.

I am no really too worried as I have a new MOT, it can rattle on for a bit longer.
 

Steve@Avantgarde

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The only requirements for MOT is excessive fluid leak or effectiveness, it could be fluid is getting where it shouldn't and causing it to be just noisy.....

Very similar systems on the W210s. The W210 wasnt leaking or ineffective either....

Make of all that what you will!
 
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duncanh

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Anybody know the part number for a self-levelling shock absorber for a s203?

It is pictured on the Russian web site, but no part number given.

If it is not too expensive, I might try changing it.
 
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Frontstep

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This thread has confused me,
if you have the spheres look in the reservoir if its black its likely one has failed.
They do thump when they have.
Febi-Bilstein sell them much cheaper than MB.
The spheres absorb the shock the other things that look like shock absorbers aren't they are hydraulic struts and just keep the car level, they are dear and can be replaced one at a time its the hydraulics that level them.

LIke this
 

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duncanh

duncanh

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This thread has confused me,
if you have the spheres look in the reservoir if its black its likely one has failed.
They do thump when they have.
Febi-Bilstein sell them much cheaper than MB.
The spheres absorb the shock the other things that look like shock absorbers aren't they are hydraulic struts and just keep the car level, they are dear and can be replaced one at a time its the hydraulics that level them.

Frontstep, Which do you think is most likely to cause the thumping, the strut or the sphere? The fluid is still a yellowish colour, it has not turned black.

I have looked in the Febi Bilstein UK catalogue, but cannot find either part for the W203. That is why I thought I would need to go to MB.
 

Frontstep

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The sphere most likely, the strut is a hydraulic ram it is feasible it could be damaged or faulty in itself or its mountings.
The usual failure is leaking and the car sinks.
Ask MB for a part number and price for your car you should then be able to cross reference with a Febi stockist.
Ring GSF or Eurocarparts as well.
They are very simple to swap.
I would guess they are the same as on a 210 but it needs checking.
 
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duncanh

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I have already asked GSF and Eurocarparts about spheres. Neither company can supply them.

I emailed a request to Inchcape Mercedes Oxford about spheres, but have not had a reply yet.

I bet the hydraulic struts are expensive.
 

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In ten years I've only had one strut go bad. It worked OK but was bent. It was diagnosed by putting the car on a ramp and lifting each rear wheel in turn with a transmission jack. The side with the bent strut returned in a series of jerks. Replace the strut - all OK

The other fault I've had is a seized bush inside the bottom pivot for the strut. That just creaks, though, and doesn't seem to affect the ride

The rear SLS, assuming it's the same as an S124, is a really simple setup. Faults seem to be 99% spheres. It's worth changing the rubber top mounts on the struts - not expensive and they have a had life

Nick Froome
 

Frontstep

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I have already asked GSF and Eurocarparts about spheres. Neither company can supply them.

I emailed a request to Inchcape Mercedes Oxford about spheres, but have not had a reply yet.

I bet the hydraulic struts are expensive.

I don't think you have spoke to the right person if you can get a part number off one that would be a great help.
They probably don't know they have what you need
The struts are around £250 ish with your discount but I would be suprised if you need one.


http://www.eurocarparts.com/suspension-sphere


Look at this for starters http://www.partsformercedes-benz.com/product_info.php?products_id=3168
 
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Frontstep

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Your spheres are the same as fitted to many others including mine, a 210 MB A1403280515

£81.60 - 25% forum discount from Eurocarparts
 
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duncanh

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Frontstep, thanks for the info. Everywhere else I have looked the only C class sphere listed is for W202. This link shows the same one fits the W203. I gave both GSF and Eurocarparts my Vin No, and they both said they could not supply.

I may buy one to see if it solves my problem. If so, I will fit the second one if the car is not level or handles badly. If it makes no difference, it is a relatively inexpensive experiment.

Those naughty people at Inchcape have not replied with a price/part number. If they do, it will confirm that it is the same as the W202 and W210.
 
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duncanh

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I got a new Febi sphere (it is the same as the 140, 124, 202 and 210) and replaced the nearside one (where all the thumping is coming from). Not too bad a job, all of the connectors came out without any trouble.

It has made no difference.

This takes me back to Steve's view that the problem is probably caused by hydraulic strut, the part that MB calls the Hydropneumatic Spring Leg. Based on my previous experiences with Steve, I thought he was probably correct (he usually is), but the sphere seemed a cheap and easy test.

Interestingly, with a new sphere on one side, and the other one having covered 305K, the car is still dead level at the back.

I don't fancy buying a new strut as an experiment. I suspect they are expensive. One for a w210 is about £270. Is there a way to test whether the strut is causing the thumping noise?

If it is the strut, does anyone know if the W203 part is common with any other models? It is shown on the Russian parts catalogue, but without a part number. If anyone has a part number, I would be grateful.

It looks fairly easy to change, just one nut at the top and a nut and bolt at the bottom.
 

Mercedes-2010

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Is this a deffo on the strut? Why not try a pair of standard struts to see if he g'dunking goes... has a subframe mount been considered.. they do go soft but still look ok! Especially on a 300 k miler...
 
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duncanh

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Is this a deffo on the strut? Why not try a pair of standard struts to see if he g'dunking goes... has a subframe mount been considered.. they do go soft but still look ok! Especially on a 300 k miler...

The subframe mounts have been suggested before. I was told that this is a very big job on the W203, and probably not cost effective.

For that reason, I am trying to eliminate everything else first.

Are you suggesting that I replace the rear struts with standard shock absorbers? Are the fittings the same? Would I just need to block the fluid line going to the struts?

I have seen it suggested that the springs would not be strong enough as they are currently augmented by the inherent springiness of the hydraulic strut. Anyone have a view on this?

The thumping is really beginning to annoy me. I don't like to be beaten.
 

Frontstep

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Dealing with wear on a high miler can be a case of checking many worn parts,
My car has done a third of the mileage and I have replaced two control arms, two shock absorbers and a ball joint at the front all had wear and all replacements reduced noise and play.
The car still has a slight knock under certain road conditions but I am fussy and will pursue it till its perfect.
If your car was a plane with commensurate mileage the entire suspension would be in bits and all parts checked.
The part making the most noise was a shock absorber !
The hydraulic strut could be the cause or its mounting, its not an exact science sometimes but an experts half hour could be money well spent in your case.
 

Mercedes-2010

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The subframe mounts have been suggested before. I was told that this is a very big job on the W203, and probably not cost effective.

For that reason, I am trying to eliminate everything else first.

Are you suggesting that I replace the rear struts with standard shock absorbers? Are the fittings the same? Would I just need to block the fluid line going to the struts?

I have seen it suggested that the springs would not be strong enough as they are currently augmented by the inherent springiness of the hydraulic strut. Anyone have a view on this?

The thumping is really beginning to annoy me. I don't like to be beaten.[/QUOTE





Assuming that standard shocks will fit it would be worth doing to test... also what about swapping left to right and visa versa. . Just to see if the noise follows the shock or stays on the same side...
 

Frontstep

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"Are you suggesting that I replace the rear struts with standard shock absorbers? Are the fittings the same? Would I just need to block the fluid line going to the struts?"

No.
 
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