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Hello everyone, my c300 has been amazing for the last few years but yesterday my first worrying issue came up. It is so intermittent and hard to reproduce but I managed to get the sound on video;
You can hear it very clearly on the video in the beginning at 0:04. I had to do figure eights to get it to act up and if it does it while turning its about 80% when I go right.
Problem is this doesn't only do it when turning, sometimes at low speeds it starts doing it out of the blue and I can make it stop by applying the brakes, even so slightly feather the brakes, it stops immediately. I did put new genuine mercedes pads last week but it only started doing this yesterdays and I double checked everything and all seems good.. It is so intermittent and only does this under 40mph once in a blue moon. I also replaced my front and rear flex discs last mouth but again no vibrations or noise till yesterday.. At this point im just waiting for it to get worse so I can actually find the source because as of now, on a lift spinning all four wheels it doesn't do it..
Any help would be appreciated if someone has heard such a noise before, from my ears it sounds like its coming from the front left wheel area, I even changed the front differential fluid to be sure it wasn't worse case but after 50k since last fluid change, the differential fluid was still relatively clean free of metal particles.
Found this and sound just like mine, should I try resurfacing the rotors ? My rotors are Zimmerman, replaced last brake job and I never had vibration when braking so I assumed they were straight when I put the new pads on but this might be my issue, bizzard that its the opposite from that video because he gets the noise when applying the brakes, I on the other hand can stop the noise when it happens as I apply the brakes. Is this some kind of dragging brake pad, I will try re greasing the caliper slide pins, maybe I missed something.
Last edited by W204Motorsports; Mar 20, 2018 at 01:20 AM.
New pads but old rotors right ? Would check the run out on the rotors to see if near or blatantly out of spec so the pads are hitting rotor setting up harmonics, like rubbing your finger on the rim of a wine glass. Slightly hitting the brakes would stop it. Enough "wobble" to make the hum noise is less than the amount of warpage needed to have your brake pedal talk back to you.
Temp of rotors from different driving/braking runs can change frequency of event. I have had mechanics change the position of the rotor after checking the run out of the hub face to try and get the best 0 run out site. Occasionally a mild run out problem is fixed by taking a wire drill wheel to the back of the rotor and hub face to remove rust/hard grime build up.
Rotors are fairly cheap to replace, certainly an easy DIY. I don't like rotor resurfacing myself..sometimes the shop just doesn't do a good job ( I has a Porsche shop resurface my warped rotors once and they were worse after....new rotors cured the problem) plus the now thinner rotors are more prone to heat warpage.
Thanks for the reply and Im glad It's not my transfer case or front differential, I was getting ready for the worse but Im relieved I found the issue and its certainly the "old" rotors on fresh pads. The fact this only happens after a longer drive means the rotors heat up and expand causing the humming. I just sent the rotors out to get machined and hopefully that fixes it, if not il just order some new Zimmerman rotors. Thanks again.
So I got my rotors resurfaced with no issues, the sound went away for a few days but last night after a long drive it very faintly tried to do it when I was turning? Do the genuine pads have some issue with the Zimmerman rotors? Resurfacing the rotors definitely helped and stopped the noise in general but it still slightly hummed on me when I was turning, Im guessing it will go away once the pads are "broken in" ? Any thoughts ?
Hey man did you ever figure out what the issue was? I have the same exact noise happening to me after I get to higher speeds on S mode. I brought it to a garage and they just cleaned the brakes and said they couldn't find anything wrong.
Hey man did you ever figure out what the issue was? I have the same exact noise happening to me after I get to higher speeds on S mode. I brought it to a garage and they just cleaned the brakes and said they couldn't find anything wrong.
Yes, it was just the new brake pads bedding in since it never did it again after a few weeks of driving with the new pads.
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