Flakrim427

Hi guys,

First off, i’ve been on MBWORLD plenty of times previously but i just registered as a member. Hello to all!

I currently drive a C43 2017 coupe, and have a loud thumping noise coming from under the car. I’ve sent it to two mechanics and they have not been able to diagnose. The bushings, and links are all in great condition… we can’t figure out whats causing it. The noise typically occurs when turning right, or going over bumps, or even backing up. I believe its coming from the right side, between the center console and the wheel. One mechanic said he believes it may be the motor mount or transmission mount.

Any thoughts? I have attached a video for reference. You could hear the noise a lot on the first right turn.

Thank you in advance!!

W205C43PFL

Glad you finally decided to join us, welcome!

As for the video, hmmm I don't see it. Could try reuploading please?

Flakrim427

Apologies, please see link below. The video wouldn't upload due to size limits.

stockbmw

Did you bring it to mb to diagnose? There few folks in w205 forum with broken steering wheel pin that might causing this. But I would expect the noise would come from the steering wheel not from center passenger side.

Flakrim427

I have not sent it to MB to diagnose yet.. afraid they'll charge a fortune. The mechanics i sent it to tested the rack and pinion. They said this wasn't the issue and it was in good condition. I don't really feel any feedback on the steering wheel.

user33

Though it seems a little loud for such a noise, my C63 S had a (much quieter) thumping/banging noise when accelerating at certain speeds/gears. I got under the car and checked all the heat-shield pieces for clearance and, where things looked close, did some "adjusting"/bending. For me, that cured the noise. If you can easily get under your car, it's worth doing such a check ... though I'd guess it's a low probability.

If you've ever watched an under-car video, you'll see that the exhaust-system piping/cats/muffler can actually move quite a bit. This would be exacerbated if a drive-train mount was wonky ... in which case you might even see visual evidence of some part coming in contact with another part (heat guard, frame, etc.). Again, worth doing an under-car inspection to look for any such contact evidence.

The other thing that I'd try to check is the shocks, as they can sometimes thump when they've failed. The ol' "bounce a corner" technique should show if a shock has failed ... but be careful, today's body panels are thin enough to be dented during such a test.

jhpmbusa

pretty sure you have personally noticed, but it sounds like it happens whenever you go over something? like a bump/curb etc

Flakrim427

Yep! It certainly happens more often on bumps especially when turning right onto parking lot cubs, etc. I used to have the same sound on the left side, and it turned out to be a bad sway bar... but the mechanics are saying the sway bars are fine now. Everything I've found online relates the sound to sway/bushings... it's driving me nuts hearing that noise.

Flakrim427

I will try this today once i get home. If i hear a sound or notice double bounces with the shocks... i will follow up with you thank you!

Aliw140

I have the same exact sound, did you ever figure it out?

Flakrim427

yes, it was the engine mounts. I was quoted like $2K to repair. Ended up just upgrading to a GLC43.

Aliw140

Ouch... thankfully I'm still under warranty. Thanks for the tip and hope you are enjoying the GLC43

W205C43PFL

Seems a bit premature for engine mounts to fail already, how much is on the odometer when this first happend?