What is the coil spring breakage problem on Mercs all about??

martin_sv

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I've read on the forum about spring breakages (fronts??) on E classes and possibly other models. The bills I acquired with my newly acquired 2006 CLK show that it has had both rear springs replaced. Does anyone have the lowdown on what is specific to MB's coils that seem prone to problems requiring replacement?
Martin
 

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Any spring will soon fail if it gets rusty and they always break at the bottom , and the last few inches. The springs can sit in water at the bottom.

Having lousy springs is good business for Mercedes, but to be truthful many cars have spring trouble these days owing to the rough state of all of our roads
 
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martin_sv

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Any spring will soon fail if it gets rusty and they always break at the bottom , and the last few inches. The springs can sit in water at the bottom.

Having lousy springs is good business for Mercedes, but to be truthful many cars have spring trouble these days owing to the rough state of all of our roads

I'm puzzled about the rust issue. Even sat in a puddle of water one would think that the degree ie depth of corrosion would be non significant in a structure as thick as a coil spring. I suppose it could be poor/cheapest steel quality selected by mercedes. There are plenty of old Fords from the sixties running around with their coil sprung macpherson struts still in one piece--- the damper in the strut would be another question altogether!
 

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Any spring will soon fail if it gets rusty and they always break at the bottom , and the last few inches. The springs can sit in water at the bottom.

Having lousy springs is good business for Mercedes, but to be truthful many cars have spring trouble these days owing to the rough state of all of our roads

It was the TOP of the rear springs that both broke on EmilysMum's Astra few years back. ;)
 

EmilysDad

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..... There are plenty of old Fords from the sixties running around with their coil sprung macpherson struts still in one piece--- the damper in the strut would be another question altogether!

Possibly because they were not progressive rate ie they were fairly thick throughout their entire length and not tail off to a rat tail at either end :confused:
 

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Almost non-existent problem here in Oz and many of our roads are WORSE than yours. My 2003 ML has done many outback KM's, towed a van regularly, carried heavy loads etc with no issues at all.
Can only be a result of salted roads and wetter climate. Once rust gets into a crack it will expand and cause crack to get larger - bit like "concrete cancer"
 

Rob law

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Springs Gone

I have had the same question all four have been changed on my CLS, in 45 years of motoring the only ones that have ever gone.

Never heard of springs going until the last few years, I would have thought that modern steel would have been better, with modern QA/QC this would not have been a problem, my wife's Clio has just had two springs changed, never happened years ago why now?
 

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If you keep your eyes peeled on the roads up here, there are hundreds of coil springs, usually the end inch or so, lying at the sides of the road.

I see them everyday, so not just a Mercedes problem.

Russ
 

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I was under the impression that EU laws had ruled out some of the metals previously used in spring manufacture, and that this was the reason that modern springs corrode more easily than older springs. And I'm pretty sure I read that here, but I don't have the time to search for it right now.
 

martinopy

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Definitely not just a Mercedes problem and a lot more common than you'd think. I have a friend who is an mot tester and he sees this problem regular across many makes and models.
 

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Found one of the posts I was thinking about, by Number_Cruncher

From the failures I've seen on a number of makes and models [it's not just MB by a long chalk!], the failure is usually where the corrosion protection has been broken and the spring material itself has begun to corrode - with the products of corrosion helping to wedge open the faces of the crack.

I don't have any hard evidence to prove this, but, I suspect a combination of factors;

1) Spring corrosion protection using heavy metal plating has become difficult or even outlawed under EU rulings

2) Springs now tend to be the progressive type where more coils come into contact with the spring cup as the suspension deflects - this allows a softer initial spring setting with better ride, but, firms up as the suspension deflects and spring coils become ineffective. This repetitive making and breaking of contact is very hard on the spring's protective coating. This, I think, explains why the failures tend to be towards the ends of the spring rather than in the centre.

I don't think it's anything to do with the detail of the spring shape at its end, as I've seen failures in pig tailed springs, where the pig tailed end coil is generally thought to relieve any extra stresses.


It's post number 58 in this thread http://forums.mercedesclub.org.uk/showthread.php?t=47669
 

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What has also happened to keep the weight down and manufacturing cost down the metal is now thinner than what it used to be, but more highly stressed, the metal used on a 211 coil spring is just over half the diameter of a 124 spring.
 

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Its corrosion induced stress fracture. Its caused by residual stress left in the spring during the manufacturing process. Once any protective coating is damaged the surface of the steel starts to corrode and micro cracks are formed- these act as a focus for external and internal stresses leading to a larger crack and failure. It's why a spring can suddenly break while the car is sat at the roadside. While nothing can eliminate corrosion springs can be made more robust by its surface being stress-relieved by heat and shot peening following winding. It can be done but costs money. It is frankly scandalous manufacturers don't insist on this from their spring suppliers.

ps if you want springs that have this treatment try EIBACH or H&R

[YOUTUBE]6ZMuMvpgKFs[/YOUTUBE]
 
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antijam

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It's a combination of factors.

As Malcolm points out in an earlier post, most Mercedes springs fail in the bottom coil. The design of the spring seat means road crud accumulates in the lower coils and combined with rain and winter salt, provides a nice corrosive poultice.

It doesn't take much corrosion to precipitate failure. Nowadays spring production is a much cheaper process thanks to manufactures eliminating a couple of previously very advantageous steps. Originally coil roadsprings would have their end coils closed and ground and would then be 'scragged'. Scragging involved compressing the spring to solid - way beyond it's normal operating range - to take the material beyond it's yield point and achieve a more even stress distribution throughout the wire. With the elimination of both these steps, modern springs have very high stress concentration at the coil surface - where a very small amount of corrosion will provoke a stress raiser sufficient to provoke fracture.

These factors combined with the parlous state of our potholed roads are at the root of the increase in spring failures. My local garage has found they are replacing more roadsprings than brake discs these days.

Interesting to compare the recently failed spring from my ten year old SLK...

P1040300.jpg


...with the fifty year old one from my Daimler SP250....

P1050561.jpg


After cleaning up, the Daimler spring went back on the car. :D
 

Frontstep

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The technical term is they are crap, its another example of cost cutting of basic components.
I personally blame Michael Schumacher and Lewis Hamilton;
my latest pet conspiracy theory is their ludicrous pay comes from cost cutting on road springs :lol::lol:

I will concoct a new conspiracy theory later :lol:
 

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It's a combination of factors.

As Malcolm points out in an earlier post, most Mercedes springs fail in the bottom coil. The design of the spring seat means road crud accumulates in the lower coils and combined with rain and winter salt, provides a nice corrosive poultice.

It doesn't take much corrosion to precipitate failure. Nowadays spring production is a much cheaper process thanks to manufactures eliminating a couple of previously very advantageous steps. Originally coil roadsprings would have their end coils closed and ground and would then be 'scragged'. Scragging involved compressing the spring to solid - way beyond it's normal operating range - to take the material beyond it's yield point and achieve a more even stress distribution throughout the wire. With the elimination of both these steps, modern springs have very high stress concentration at the coil surface - where a very small amount of corrosion will provoke a stress raiser sufficient to provoke fracture.

These factors combined with the parlous state of our potholed roads are at the root of the increase in spring failures. My local garage has found they are replacing more roadsprings than brake discs these days.

Interesting to compare the recently failed spring from my ten year old SLK...

P1040300.jpg


...with the fifty year old one from my Daimler SP250....

P1050561.jpg


After cleaning up, the Daimler spring went back on the car. :D

Just look at how thick the coil is compared to what we have now days and nowhere near as highly tensioned.
 
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martin_sv

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I think my question has been answered very satisfactorily--thanks to all. Both the eibach video clip and The SLK and the daimler pics clearly demonstrate how todays' standard product is inferior to what went before. It made me think that properly made springs eg Eibach seem something of a bargain when you realise how much effort goes into making a premium product!
 

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Just look at how thick the coil is compared to what we have now days and nowhere near as highly tensioned.

there is, as has already been mentioned, the fact that on older springs, they are wound in a manner that makes the coils at each end 'meet' with its next one, and they are ground in such a manner that they will stand up on their own, unlike the more modern springs!

many cars in the 80's (the older end stuff when I started in the motor trade) still had 'relatively' flat tops/bottoms (especially non mcpherson strut set ups like the rear of a ford sierra) and, if im honest, they were about a similar thickness (from memory) to the ones on the front of my 203. and i can not ever remember having to change a rear spring on a sierra/granada! (and i owned both too)
 

graham power

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coil spring breakage

as the owner of a vito van 7 years from new the only serious problem i had was over a short period all 4 coils broke in exactly the same place the top of the first coil shears and the van droops slightly to its creadit the van remained useable each time non mb springs were only 80 pnds each and were much thicker than mb ones, labour was just one hour from non mb garage easy job for any mechanic
 


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