OutlawsMerc

Hey strangers,

Hoping someone would have a clue on where to investigate here, or what else would be helpful to communicate to a mechanic. I've recently gotten a 2014 E550 4matic, and the car seems to be great except for one concern. At random times I can both feel and hear some type of "bounce" coming from the driver side front wheel/suspension area, or maybe through the steering wheel itself. I had the car in at my local indy shop for a quick review, and they weren't able to recreate the issue at the time. They did lift the car and checked the front brakes & suspension, but reported no apparent issues there. Unfortunately, I noticed the issue was still present on the drive home. The worst part of the issue is it's intermittency, it can happen a few times within a couple minutes and then disappear for 20+. Please find some extra description below, or let me know if any more details would be helpful.

- The "bounce" only happens 2-3 times per instance, never more.
- It is best felt with a hand at the 9' position on the steering wheel.
- It both sounds and feels vaguely like bouncing a basketball? Or like the crash of a drum cymbal?
- It does not seem to make any harsh thud, clank, grinding, or other 'metallic' sound
- Always felt between 30 - 60mph, have not experienced the issue at low speeds
- Always felt when driving straight or on slight bend.
- Haven't noticed it occur in any tight low speed or parking lot turns.
- The behavior does not seem to correlate directly to any road condition like cracks or uneven pavement, but I need to research more here.
- I haven't found a way to directly reproduce the issue, other than driving on a road at those speeds for 15+ minutes.
- I have been able to drive the car for 25+ min without experiencing the issue.

Let me know if any of that indicates where I should search further, and thanks for reading!

CaliBenzDriver

Your car has developed a pronounced bounce. Your short list may involve:

• stab link + bushings + Lwr Balljoints
• (Airmatic valves)
• 4Matic CV joints

Test to pinpoint freeplay or replace these maintenance parts.

++++++
While in the bouncing Dept... if your car frequently rocks side to side: it's the rear stab links bushings that help cause this.
The front stab link uses ball joints and are more resilient.
So just replace the 4x cheap stabilizer bar links: done! ✌️

ChrisHimself

sway bar links go out on these every other year about its pretty hilarious
lil too soon for control arms, mine were "ok" at 150k of terrible driving. The bushings aren't as hollow as they used to be
Also transmission mount could be roached. those can go out every 5-6 years depending on your conditions even if this isn't your actual problem I'd look at that.

Sway bar links are 1hr each side billable, so probably $300 labor and $100-200 for the pair depending on what you get from who

OutlawsMerc

Thank you both for the quick response! Cali, I see you sharing detailed expertise across many threads - I always appreciate the knowledge found on these forums.

This car is just over 70k miles, for reference. The good news is that I haven't noticed any adverse impact to the driving experience other than that brief "bouncing" sensation - there doesn't seem to be excess side-to-side sway at the time of that sensation or while driving otherwise, but I will monitor this more closely. I'll try some more low speed & parking lot driving as well, to see if it ever occurs in those conditions. When looking at the tires just now, I see that three are a 2020 date - but the front driver tire is a 2018 date? I have it scheduled for an alignment check, and will have them check & rotate the tires to see if the sensation follows at all. New tires are in the future in any case.

OutlawsMerc

Still unable to reproduce at any speeds under ~30. Including a video of the noise as well, this happened around 50mph on a straight smooth road. There are two "bounces" around 4-5 seconds. Video example

CaliBenzDriver

Wait, I heard the "bang-bang"....
that sounds exactly like the steering wheel shaker.

OutlawsMerc

Feels like we are narrowing in! I'm trying to find the part number for that, do you see the component you're thinking of on https://www.mercedespartscenter.com/ or https://mbparts.mbusa.com/? Maybe the 'steering wheel damper' (166-906-31-01), or could it be part of a larger assembly?

CaliBenzDriver

vibrator assembly
vibrator warning can be turned off using the display memu options

OutlawsMerc

Cali, thank you again for the assistance here!! I'm seeing where part A2129062700 may be for the pre-facelift W212, with most websites are showing it as incompatible with the 2014 model? Trying to find the comparable piece for the post facelift MY - might one of these.

Steering Wheel Damper 166-906-31-01
Steering Column Tilt Motor 218-906-28-00
Motor Assembly 172-906-05-00

Assuming the alignment & tire swap makes no difference, and I don't believe that it will for this, I'll follow up with my local shops and show them the video as well.

WRC-LVR

Try turning off the vibrator warning in the display menu options. If that fixes it, then you at least know what causes the shake. Now why it is doing so.. is probably a sensor for the active lane keeping assist. That system may need calibrating....or a sensor needs replacing plus system recalibrating..

OutlawsMerc

hahahaha - my first two threads are a remarkable example of my mechanical prowess. Essentially, "why is there excess condensation when it is very hot/humid" and "why is LKA working as designed". The video below seems to demonstrate the feature, and is probably where I should have begun. With the LKA system disabled, I did not have that sensation in 2+ hr of driving. Setting the system to 'adaptive' instead of the default 'standard' would probably reduce the number of detected violations, so I will experiment there - a majority of this driving has been on windy back roads, vs interstates. Thanks again to all

CaliBenzDriver

That's great!
Glad we could help you find a solution.

Now you can get back to reading about schedule maintenance to prevent expensive surprise.