Hey guys, well it's been a couple months since I bought my C230K Coupe and I love this car! However, since I bought it it's had a "knock" noise in the front driver side when I hit pot holes or some uneven pavement/bumps. I contacted the stealership and they said it's most likely a control arm and they'd need to replace both sides, possibly upper and lower. You don't even want to know what they want to charge me to do this job.

I believe the stealer said the knocking noise is most likely due to a worn out LCA (not sure if this is due to bushing, bearing, or both?), but I've read from other sources (including this site) that this knocking noise can be due to an UPPER control arm and/or sway bar link and/or tie rod?

So, I decided to look up all the part numbers for the entire suspension, find the best prices, and possibly replace every single part.

1) Any opinions on what the "knock" is most likely caused by?

2) Am I wasting money replacing any of these parts other than the (4) control arms? I've read that the bushing on the LCAs are junk and this is a common problem with this model (or Mercedes in general? amazed MB hasn't re-designed these things), but am unsure if the other suspension parts wear out as quickly and might need to be replaced at some point as well. My thinking is if I'm going to have my mechanic under there, might as well get as much done at once as possible and stave off any potential future problems. I know everybody's philosophy on this varies and some people prefer to fix each problem as it crops up, but I tend to like preventative maintenance....

Thanks in advance for your advice and insight guys!

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C230K Coupe Suspension Replacement parts list (all of the following are going to be Lemfoerder except where otherwise noted):

Checking prices at RMeuropean.com for all of the following totals $1217.76. OUCH. I think I can beat that by a fair amount by using mbpartswarehouse.com instead, but the search function on RMeuropean is much easier to use. I already ordered new Koni FSD shocks (~$630) and the Eibach Pro Plus kit (springs/sway bars/bushings) (~$430). Soooo, another grand + on top of that expense is starting to make my eyes cross. lol Still, I do love this car and want it to run as long as possible as a daily driver, occasional back-road/twisty fun-mobile.

Must replace:

1) Control Arm Left Front Lower - Part Number: 204-330-19-11
2) Control Arm Right Front Lower - Part Number: 204-330-20-11
3) Control Arm Left Front Upper NOTE: Includes inner bushing. - Part Number: 204-330-43-11
4) Control Arm Right Front Upper NOTE: Includes inner bushing. - Part Number: 204-330-44-11

Optional stuff:

1) Control Arm Rear (2 Per Car) - Part Number: 202-350-02-06 (Genuine Mercedes)
2) Support Arm Rear Suspension (2 Per Car) NOTE: Also Use- (1) 210 350 45 06 Camber Strut Mounting Kit (1) 210 352 00 43 Bushing Insert Sleeve - Part Number: 210-350-33-06
3) Tie Rod Rear Suspension (2 Per Car) - Part Number: 203-350-07-53
4) Camber Strut Rear Suspension (2 Per Car) NOTE: Also Use- (1) 210 350 45 06 Camber Strut Mounting Kit (1) 210 352 00 43 Bushing Insert Sleeve - Part Number: 210-350-34-06
5) Tie Rod End Left Outer - Part Number: 203-330-39-03
6) Tie Rod End Right Outer - Part Number: 203-330-40-03
7) Tie Rod End Inner (2 Per Car) - Part Number: 230-338-00-15
8) Tie Rod Rear Suspension (2 Per Car) - Part Number: 203-350-07-53
9) Sway Bar Link Left Rear To Control Arm - Part Number: 203-320-07-89
10) Sway Bar Link Right Rear To Control Arm - Part Number: 203-320-08-89
11) Sway Bar Link Front (2 Per Car) - Part Number: 203-320-28-89
12) Camber Strut Mounting Kit Rear Axle Contains: (2) Bolts (2) Nuts (1) Sleeve (1) Flat Washer (1) Lock Washer (2 Per Car) - Part Number: 210-350-45-06 (Lemfoerder)
13) Control Arm Bolt Kit Lower Inner Contains: (1) Bolt (1) Nut (2) Washers (4 Per Car) - Part Number: 000-330-00-18 (FEBI)
14) Bushing Insert Sleeve For Rear Suspension Strut Bushings. (12 Per Car) - Part Number: 210-352-00-43 (FEBI)

 

Unless this cars has been in an accident or has 18" or 19" wheels and see potholes as a fun challenge,.... you shouldn't need all those components.

My suggestion would be to get the car up on a hoist and check for play between various components,.... especially the bushing. Those are usually the first to go and they're made to be replaceable.

 

Kudos to you for having done your research and homework.

Respectfully suggest first definitively ascertaining the true source of its “knock” noise.
I’d suspect the anti-roll (sway) bar’s inner mounts or links as possible culprits, with torque arm bushings running a close second.
Didn’t see the MacPherson struts’ upper bushings on the list, but they’re also a possibility.
Fact is I’ve replaced almost all of that hardware during my C’s ~110,000 miles...several more than once.

No sense throwing good money after bad, but a solid chassis makes the other repair expenses more palatable.

 

Thanks for the common sense advice. I'm going to have my mechanic get it up in the air this week and take a good look under there.

 

Thanks for the helpful response! I'm not a mechanic, but am learning about this car as much as I can little by little so in the future I'll hopefully be able to handle some of the smaller maintenance issues myself. In the past I've pretty much only worked on Japanese vehicles, so this is still foreign territory for me. I'm lucky in that I have a family mechanic who is experienced with MB vehicles and is happy to let me observe/learn/assist, which should help in the long run.

So, I'm assuming I'll have to replace at least a couple of the front control arms, but it'd be nice if I "only" had to worry about strut bushings = cheaper to replace, right?

A few quick questions that I'm still a bit confused about:

1) "Torque arm bushings" = lower control arm (LCA)? "Thrust arm" = upper control arm (UCA)?

2) I understand that if I replace the UCAs (thrust arms) these parts include the bushings, but do I also need to order bearings for the upper arms?

3) Likewise, if I need to replace the LCAs (torque arms), I've noticed they don't say they "include bushings" or bearings, so do I need to order bushings/bearings separately even if I order new LCAs?

I'm under the impression that if I replace the UCAs and/or LCAs then that simplifies the install (and significantly lowers the amount of time needed), but I'm unsure what other parts I'll need besides the control arms if I go that route. If I still need to order bushings/bearings if I buy the LCA/UCA, then what exactly is the point of paying more for the entire control arms?

Thanks again for your help!