Front spring broke season 2

[Kyiv]

Well just 2 years ago I've had a 5 year/20k mi old genuine Merc front spring break with an accompanying BANG while driving. Had both front springs replaced with a few years old genuine Merc units bought off a member @northNH here. The replacement used units had some patina rust on them from 2-3 New Hampshire winters, but nothing significant, as, again, they were 2-3 years old.

Today I was under the car, playing with an adjustment of a transmission's pressure regulator and while giving a cursory look over saw this . So this is a second Merc spring to break on me in 2(!) years. Same exact location: front passenger side



During the past January, while the car was resting for the salt season, I've replaced both front lower control arms and both front springs were fine. I took great care to reinstall them properly. I started driving the car again in late April and covered abot 3,500 miles since, and don't remember any loud bangs.

What are the phaking chances for the x2 fresh Merc springs to break on the front passenger side in 2 years? Bad luck + coincidence that it happenes in the same location?

 

[gsxr]

If it happens a third time I'm going to suspect the car is allergic to you!

Bad production batch or something? These failures are already kinda rare, two from near-new springs is nuts.

 

[Kyiv]

Here's a collage of both springs (from 2 years ago is on the left), looking towards the front of the vehicle. It seems both broke in the same spot, in a similar manner.

 

[JC220]

@Kyiv do you know the condition of your shock absorbers? Have they been replaced at any point in your ownership?

If there are any bad suspension joints or bad shock absorbers that could lead to fatigue and cracking of the springs.

At our annual MOT / inspection they use machines to test the function and health of the cars shocks. I did note my high miler w211 used to crack springs pretty much every year and I did discover whilst watching the test take place that car had bad shock absorbers! However the MOT centre was still passing it anyway so go figure.

But I did think in my case the bad shocks were quite probably contributing to the rate that car was breaking springs.

 

[Kyiv]

@JC220, hey-hey!

Suspension has been completely renewed on my car with Mercedes and Lemforder parts.

When the first spring failed it was, at the time, 5 years/20k mi old. Struts (Sachs 115-070) and aftermarket TRW control arms were installed at the same time (2015) with springs, so were the same age. New steering links (Lemforder) and idler arm bushing (MB) were added later (2019), before the spring broke (2020)

To replace the 1st broken spring, I purchased a set of both front springs + both front struts (MB with correct # numbers) that were used, 2-3 years old units. They were purchased from a member here who has an E420. He upgraded his suspension to Sportline and put up his standard E420 suspension for sale. So, when new used springs went in, 2 new used struts went in as well. All steering links were already replaced a little prior. With this set up, I drove for almost exactly 2 years and 25-30k miles. The only trailing competent from 2015 were the aftermarket TRW control arms, which I've replaced in January (5 months ago) while the car was resting for the winter, with proper Mercedes ones. In January both springs were fine. I've removed and very carefully reinstalled them back.

*These are the used units that went into my car in 2020 when the first spring broke:

 

[a777fan]

Hey there @Kyiv !

Thats an odd one. Your first picture in the comparison shot clearly shows that the fracture surface wasn’t compromised by rust, so the only thing that comes to mind is a manufacturing defect.

Not sure how long the second spring has been cracked, but on that one the fracture surface appears completely knackered with rust.

Perhaps the location of the fractures is just an area of high stress within all 124 springs? And your first set succumbed because of, as dave stated, a bad manufacturing batch? And perhaps the second one had more rust lurking under the plastic/paint coating that initially met the eye?

Otherwise- if you’ve literally replaced everything else, is your upper spring perch in good shape and aligned properly? IE - hasn’t been damaged in an accident or something similar?

 

[Kyiv]

if you’ve literally replaced everything else, is your upper spring perch in good shape and aligned properly? IE - hasn’t been damaged in an accident or something similar?

There doesn't appear to be any anomaly with the spring perch visually. When I removed and reinstalled both front springs in January during replacement of the after market TRW control arms with proper Mercedes Sportline units, the spring went into the upper perch nice and smooth, in an unconvoluted way. Hopefully I have been just unlucky.

Here's a picture of replacement springs #124 321 3904. They are still in dealer's hands. They are of a fresh manufacture and are, unfortunately, marked blue and red. My current ones are both blue, so I've ordered fresh shims for red and blue as well, and this will delay shipment of springs and shims until at least Wednesday of next week

 

[a777fan]

One blue, one red? Thats a bummer. Hopefully you wont have too much fiddling to do to get it even up front.

 

[Kyiv]

One blue, one red? Thats a bummer. Hopefully you wont have too much fiddling to do to get it even up front.

yeah. it should be alright, as I'll use an appropriate shim for each color (per EPC). that should even them out