2007 CLK - elusive front suspension clonk.

Droverunner

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2007 CLK 220 CDi Sport. 2014 S-Max 2.0TDCi.
The CLK (Sport suspension, AMG wheels, 40 series front tyres) we've owned for almost 2yrs... now on 130k... has always been a bit noisy on the front suspension but only on short sharp low speed bumps... never when at speed on bumpy roads. As I worked through the front suspension where there was play evident I thought all the clonks would go... but not yet.

So over the past year I've.... checked the springs... checked and adjusted wheel bearings... replaced the lower rear arms on the front suspension (the black ones)… replaced track rod ends... checked rack inner track rod joints... replaced anti-roll drop links... replaced anti-roll bar with OE Mercedes (bonded bushes).

Today it passed the MOT with no advisory items and that despite me mentioning the clonks to the tester who didn't find a bit of play. Likewise pre-test yesterday I had it jacked up and not a hint of play even when testing with a 3ft bar and loading the wheels from under with the bar etc.

So far we have lost the clatter of the drop links... the knock caused by the lower rear arms with play at the hub balljoint end... the knock of failed anti-roll bushes... the clang where the bar had shifted sideways and was hitting a lower arm.

Overall it's much better for all the work done but we are just left with this deep clonk on sharp bumps.

As far as I can think left to investigate are the upper frontmost (silver) suspension arms... strut top mounts... the shock absorber struts.

Anyone chased down an annoying noise like this that turned out to be one of the items we've not yet done?
 

LostKiwi

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My r129 developed a bad clonk from the front end. New strut mounts cured it.
 

Uncle Benz

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The forward arms on the front, referred to as the caster arms (the ones you have already replaced are the camber arms), anyway, the caster arms have a hydro bush at the front end and a balljoint at the hub end. The hydro bushes make a heavy knock on short, sharp speed bumps when they are worn out. I'm 99% sure that is your problem.
 
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Droverunner

Droverunner

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2007 CLK 220 CDi Sport. 2014 S-Max 2.0TDCi.
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Ok thanks... two things to concentrate on checking.

Are all the aftermarket hydro bush arms actually fitted with the correct bush... or do some cheat and just use rubber??
 

onefortheroad

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Me -2019 GLC 350 coupe AMG line. Mrs- ford kuga 65 plate awd powershift .
Shocks and top mounts. ? GOODLUCK with this issue.
 

JBell

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The forward arms on the front, referred to as the caster arms (the ones you have already replaced are the camber arms), anyway, the caster arms have a hydro bush at the front end and a balljoint at the hub end. The hydro bushes make a heavy knock on short, sharp speed bumps when they are worn out. I'm 99% sure that is your problem.

This, I had the same on my W203, replaced with Lemforder Arms from ECP
 
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Droverunner

Droverunner

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2007 CLK 220 CDi Sport. 2014 S-Max 2.0TDCi.
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Thinking through what makes the noise happen and it's particular sound I'm inclined to go for those forward upper arms first.

Seems Lemforder are £180 a pair… Monroe £110 a pair... FAI £130 a pair... Quinton Hazell £100 a pair... Borg & Beck £86 a pair... budget/unbranded £70 a pair.

Found a procedure which looks OK...

 
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Droverunner

Droverunner

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Well 3mths on and I've finally got round to this despite constant grumbles from Mrs D that the clonk was embarrassing when taking others in the car.

The front upper arms that looked OKish on the car both had loads of bush separation once removed and examined. Also one balljoint looked odd when closely examined and I found it had been craftily smeared round with black silicone to cover up a split gaiter underneath.

With the arms changed the car is tighter to drive on country roads and the sharp clonk on low speed town bumps has gone at last.

Some will grumble but I fitted Quinton Hazell arms on offer at £85 inc post the pair. Too cheap to be any good??... well they work fine now so we'll see how they last.

While I was at it I swapped the worn rear ARB bushes.

Front suspension arm bush.JPG

Front suspension arm balljoint.JPG

Rear ARB bush.JPG
 
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Droverunner

Droverunner

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Yep appreciate the reminder. I'll send Mrs D in with it next week before it's covered much more than 20mls on the new arms.
 

Wighty

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Had exactly the same noise from my CLK recently , swapping both control arms sorted this . I was due to get the tracking done , but decided to change the other ball joint on the back of the hub as well (track rod end) .
Then I got the tracking done . Totally changed the drive and removed the clonking noise .
 
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