A couple of weeks after replacing the front thrust arm bushings and struts I get a knock when I am turning to the right into a driveway and the wheel contacts the curb.

• Checked the torque on the top of the strut mount bolts and the strut shaft bolts.
• Inspected the inner part of the mount for any sign of contact between the shaft nut and mount and did not see any signs of contact
• Inspected the bushing part of the mount and it looks like new
• Raised the car and moved the wheel for any free-play and have found none
• Noticed the ability to rotate the thrust arm more than would have expected with very little resistance. First suspected that the bushing bolt wasn't properly torqued but then found that the bushing seemed to have some free-play about the arm's axis. On closer inspection noticed that the inner diameter of the rubber part seems to slide on the white plastic piece. Don't know if this is a sign that the bushing is broken or it is supposed to do this. Attached a video (poor quality). The movement of the rubber relative to the white plastic shows up best in the beginning and end of the video. Have to say even it this is not right don't know how that would translate to a knocking noise.
• Plan to to check
  • brake bolt torque and other strut bolt torques.
  • Sway bar link
  • Sway bar bushings
• If nothing is found then might disassemble strut, inspect it for noise, if none found rebuild with new mount and bearing.

 

From your video... we see the metal center of the bushing is loose... that is wrong!

This is supposed to be pinched tight with high torque (80 to 120lb/Ft) while suspensions are in neutral position with wheels on the ground.

 

Cali - Thank you for your interest and taking the time to look at the video and your comments.

I was really hoping that the bolts were loose but I just checked the bushing bolts and they tight enough such that my wimpy twisting of the control would not cause slippage at the bushing / frame interface.

Having said all that I think the poor quality of the video may be misleading you. First of all it needs to be clear how I am moving the control arm. I am twisting it about the arm's longitudinal axis. So the outer part of the bushing is rocking about a point 90 degrees from the axis of the bolt through the bushing. What I think I am seeing and is in the video is that is that the inner portion of the rubber bushing that is in contact with the white plastic part that the bolt goes through is sliding along the plastic. I can twist the arm say a couple of degrees and the arm is content to stay in that position. I would have thought that the stiffness of the bushing would have returned it to center but as the rubber appears to not be like glued to the white plastic center bit and is happy to slide over to a new position.

So the question is, are the new bushings damaged (they both do this) or are they supposed to be that way?

I also have twisted the sway bar link and am not detecting any free play there either but thinking I will disconnect it to confirm.

 

Ok, so the control arm bushing is already loose from its center core.
This is not great but that's not causing your clunking issue.

You don't say anything about the two ball joints of the control arms...???

What about the two ball joints of the steering tie-rod: any freeplay in there...???

The swaybar bushings are not the best. Can they clunk while turning, perhaps but unlikely. They can get noisy on washboard roads.

Next is back into strut hardware. What did you replace on L vs. R side: strut bushing + spring bearing ??

 

Ok, so the control arm bushing is already loose from its center core.
This is not great but that's not causing your clunking issue.
I agree

You don't say anything about the two ball joints of the control arms...???

Rebushed the original control arms. The ball joints felt tight. Can not detect any free-play in the wheel when move it left or right or up or down.



What about the two ball joints of the steering tie-rod: any freeplay in there...???

Replaced the drivers side tie rod end because I observed freeplay in it and it clunked when I drove out of my driveway.
No detectable free-play in either side now.

Any better methods for identifying bad ball joints?

The swaybar bushings are not the best. Can they clunk while turning, perhaps but unlikely. They can get noisy on washboard roads.

Agreed

Next is back into strut hardware. What did you replace on L vs. R side: strut bushing + spring bearing ??

Did not replace bushing or bearing on either side. Bushing looks good and no contact between strut shaft nut and inner part of mount observed.


My next step will be to remove sway bar link to further check for freeplay though I am not finding any in situ.

 

Question: Do you think that it will be possible to remove and rebuild and reinstall the strut and not need to have the front end realligned?

 

Yes 100% to that.
What messes alignment is... new tie rods.

Replace strut bushing + spring bearings at once on both sides - It's a seriously bad idea to do any one-sided work on suspension parts, both front or rear.

Ball joints are bad before the ball wobbles in the socket
Think of rubber bushings as rubber springs... 10Yr old, they are chewing-gum grade unanle to handle dynamic forces.


> CLEVER RELATIONSHIP:
Somewhere else I wrote how the bad strut bushing brakes up the plastic bearing race holder.
When the strut shaft is allowed to move around, it brings with it the big coil spring. The plastic bearing race support can't stop the spring from traveling.... clunk-clunk! The spring follows the strut.
The spring carries the whole weight
​​​​​​the strut guides it precisely without any static 500Kg weight smashing the rubber 24x7.

replace at once when steering wheel is no longer crisp and precise.

 

I am ok with rebuilding the struts with new mounts and bearings and I will replace the sway bar link while I am at it as I only replaced it on the other side.

 

don't do suspension job half-way on side only - It makes the chassis unstable with dangerous reactions at higher speed.

The clunking is the plastic bearing holder asking for replacement - Of course a shop would junk the strut as well but if the shaft is dry, you can hang-on until the seal gets compromised and nitrogen leaks out.

+++ front stab links calls for rear stab links too and ultimately the front stab bar itself because it's the wear item that kills the hot struts by bouncing unstable - Meaning change stab-bar before struts!

 

The struts are brand new.

 

now you know what to do. Don't beat yourself up!
A lot of issues can be extremely misleading starting with misfiring DTC's.

The bounciness is caused by weak sway bars before the struts grow sick and tired.
MB Suspensions handle heavy forces but are very touchy regardless.

The spring clunk is caused by bushing moving around.

Mercedes logic is multi-level : things are rarely what they appear.

 

Fred,

The video is not too "clear" as the bolt is not visible.
Will compare it to mine and with engine steel plate protection removed, so its a better view.
Let me work on my wheel first yah...

 

Here u go.............. should be up and running in 20 minutes after I post.

 

Thank you for doing that! That is what I expected. But to be completely clear that is the thrust arm also called the upper control arm, the one that connects the wheel to the forward frame member, you perform the caster adjustment to this bolt correct?
Assuming that is the case, it looks like the newly installed bushings have already broken. I don't understand how that happened because I did support the weight of each side of the car with the wheel prior to tightening them.

 

WIS call that arm as Caster Arm.... but not EPC




The Rear one is called CAMBER arm.




I find it easier to name the arm for its function or when correction bolt is needed.

 

Ok Did you manipulate the caster or camber arm? I am concerned about the caster arm. Though truthfully I expect the same result.

 

Yes, it was a really great learning process....... that is why I am very familiar with ride height pre-tension on the bushings and the DO and DONT when doing suspension arms.

Read here : https://mbworld.org/forums/e-class-w...adventure.html

 

I kind of suspected it was the camber because of how long the bolt protruded from the nut.

Still not sure how the caster bushings will behave if you twisted those the same as you did the camber arm.

 

It will behave the same way, it is just Camber arm bushing is a bit smaller as its duty is not as severe as Caster Arm.
I test these arms often with pry bar

 

Thank you!

 

Fred,

I am under the car again today, so I thought of your car......

On the subject of the CAMBER arm.
I tried playing with it and it is VERY VERY tough to twist of shake, because its rubber bushing is on purpose made very thin, as to not allow much freeplay.
This is based on my RWD Camber Arm, item #300.





I do not know your VIN, so I am using W212.087 as 4-matic with M272 engine which yours is , being a 2010




Just to make sure component wise you have replaced the correct bushing P/N :

01. Your CASTER arm bushing #110 is not the same as mine, if bought bushing only. Yours seems to be the hydro version, hence it has 2 end caps item #115.
Your #110 bushing A212 333 03 14 ( called bearing LOL ). Yours has 2 end caps #115. Attached its WIS in PDF
Mine #210 bushing A212 333 00 14 ( called bearing too ). Mine no end caps.



Our Camber arm difference.





See how thin the rubber part of the bushing is for my Camber Arm :





Mine - RWD



Mine





Your Camber arm has its on ball joint, I marked it as A.
Me, I got to buy separate ball joint, it is L shaped #310.
This L shaped ball joint is a comfort ball joint and does not last very long. I have replaced mine after track use. Its okey, no sound , but its not as
tight as new anymore.


Any ball joints cam also create a knock if it is worn out.
You have two of them, on your Camber and Caster arm ends.

This is why best to replace Camber or Caster suspension arm as complete assy, easy and worth it if in your case where they both have ball joint at the end.

Happy troubleshooting..........

 

Thanks for the comment. The bushing of concern is the front caster arm bushing. Based on your prior comments I am assuming that it would provide similar resistance to being twisted as you demonstrated on your camber arm. That being the case I think that the bond between the rubber bushing and the OD of the inner pin must have failed. I have to say they act similar to prior to their replacement which is what prompted the request from you. Part of the point I am making here is that prior to rebushing them and replacing the struts. I had zero noise in the front end. So I am guessing even though they are not right, since they seem similar to how they were previously, I am thinking based on comments from Calibenz, and the other thread were the gentleman had noises that he cured but replacing the mounts, that the noises are strut mount related. Unfortunately we are headed for a bit of a cold spell and my garage isn't heated so it will be a little while before I get the struts back out and take another look at them.

Relative to buying new arms vs rebushing mine. I did consider doing that but; a) My ball joints seemed tight and it seemed like a shame to through them away particularly considering that the part without the bushing cost over $500 each at the dealer. b) could not find arms that contained the OEM bushings and when I researched reviews of the other brands I was very concerned that they weren't hydraulic and would not give the factory road isolation. c) If I was able to get them rebushed and installed myself for like $80 each that felt like a big win.

One interesting comment on your camber arms. They look much nicer than mine. Mine are more rod like whereas yours look more like the caster arms. Nice formed pieces. The must have improved them with the face lift.

 

.

 

Just wanted to provide feeback that replacing the strut mounts, bearings, spring pads and bump stops on the new Biltstein B4 struts did eliminate the steering knock that I was experiencing after the initial strut replacement.

Thanks to everyone that provided me guidance on this work.

 

good info