Baldur!

It's another issue I discovered during the 1st month of driving, but it is more important one, so I decided to create separate thread for that. I had it already several times, but I preferred to drive more hoping that it will solve but itself. I did already >2.5k and it is still there. I tried to push/pump brake pedal, it doesn't help.

So, the issue is, that sometimes when I slow down in order to park, the brakes are very noisy, like they are not fully released after braking (normal, let's say going from 50 km/h to 5-10 and slowly approaching parking place etc.). Sometimes they are noisy when I break, sometimes even without touching the pedal. I've managed to make 2 short movies when you can hear it, but sometimes it is even louder. I wonder if anyone had this problem?

hlieberg

I wasn't able to hear anything in the videos. But if you are talking about a squeaky noise, this is normal for performance brakes. This is also commented in the user manual.

Baldur!

I guess the volume has to be put high enough, but it should be quite easy to spot. The noise is of whoooooo type, not squeaky.

White One

They are probably just not hot enough. I have had this happen with my other performance type cars..(S4, CTS-V, and M5)..My 450 seems a little better than they were.

Baldur!

I see, but why I hear this sound even though I'm not braking? For example 50 km/h, apply brakes to slow down to 5-10 km/h (no noise), then release the pedal and noise is there (both while not applying or gently applying the brakes).

Mr. J

Might be a stuck caliper or a stone or piece of road debris stuck in there. You should get it checked out.

Baldur!

Yes, my feeling is that left rear brake disc was a little bit more hot than the right one - so maybe stuck caliper. Will check it next week. Thanks!

mcschan86

i have this same issue about brake noise at very low speed, especially when braking to 5-10 kph and releasing the brake to let the car roll slowly. but mine is not a hoot-type sound but a squeak type. it synchronizes with the wheel rotation and the noise activates after brake is pressed and let go. someone suggested that it might be a warped rotor. it's more apparent on colder temperature, although i can hear it during the summer.

someone suggested that it might a warped rotor but i haven't got a chance to look into that yet.

Baldur!

What you have described is exactly the same behaviour, apart from different type of noise. I hope we will have the issue resolved quickly!

Baldur!

To update on the topic - finally MB replaced the rear brakes (under warranty). The noise was gone...for about several hundreds of kilometres, now it is back...

Do you think it may be related to my driving style? As I live in Switzerland, I don't have many opportunities to brake hard, as most of the time I don't drive aggressively (one of the reasons C43 is more than enough for me ). Maybe I should try to brake heavily few times so the pads and discs align better? Can you recommend any procedure how to do it properly? Should it be done from time to time or just once?

Forgot to add - now the situation is even worse, as after their intervention I've started to observe vibrations while driving around 50 km/h - mostly on the seat, but a little bit on the driving wheel too... Can it be related with rear brakes also?

superswiss

It's been said many times here and in other places. Performance brakes need to be bedded in for proper operation and performance. Noise, vibrations etc. are most often a result of not bedding in the brakes and either have the pads scrape against the bare metal of the rotors or you end up with uneven pad deposits and then you have vibrations. Performance brakes are designed to stop these cars from high speed, repeatedly and to get hot. Not using the brakes at that level at least once in a while may result in issues. In climates with snow and salt during the winter like in Switzerland, you will also have corrosion sooner or later. Using the brakes properly will also remove surface rust that may have built from the water and salt on the roads. Once some form of normal life returns, take the car up and down a mountain road once in a while. Plenty of those in Switzerland and yes I know all about the state of speed enforcement in Switzerland, I was born and raised there. Not sure where you live, but hit up some of the nice mountain passes that don't have all that much law enforcement. Places like the Klausen Pass, Oberalp, Furka etc. or if you wanna venture a bit into Italy make a trip to the Stelvio Pass. I was there with my C63S last spring after taking delivery of it in Sindelfingen and hit up many of them.

Here's a fairly good video about bedding in the brakes and how to do it.

zibby43

Good advice. The brakes on my departed ‘18 C43 were covered with thick rust deposits from the car sitting on the lot for a long time during months of unusually heavy rainfall.

I tried bedding them in to remove the rust (didn’t even come close to working). They removed the rotors and discovered corrosion on the hats and inside portions of the rotor.

Dealer replaced the rotors and pads under warranty and a mechanic bedded them in prior to releasing the car to me.

Anyway, here is a photo of what the OEM rotors look like when they’re still factory-fresh and coated:




And after a preliminary bedding-in:

thwgw24

Hi OP,

See attached videos. Is it the same noise you are getting? I am hearing the noise only when rolling at very low speed (under 10 mph), brake paddle just released. Usually in parking lot or taking off at stop light. Once it picks up the speed, I can't hear it.
Purchased my vehicle beginning of February. MB replaced both my rear rotors and pads early March. Noise disappeared for a week then came back. They are going to take another look this Thursday. Technician told me he'll try to replace the wheel bearings. I'll update afterwards.

Baldur!

Thank you superswiss/zibby43 for info about proper bedding!

Yes, it is exactly the same! I hope it will be sorted out for you this time. Please keep me posted - my garage is currently closed due to covid, but if yours find a solution (of course if it is not just connected with bedding), it will help me a lot.

thwgw24

I am almost certain it has nothing to do with bedding as the noise comes up when not applying any brake. I’ll definitely keep you posted.

superswiss

The brake pads always touch the rotors slightly when not applied. There is just no pressure applied to them, but if you have uneven deposits on the rotor, those high points will cause a noise every time they pass underneath the pads.

thwgw24

Good to know. Thanks Superswiss.

thwgw24

The dealership is keeping my vehicle for another week due to other issues but I was told that they replaced my rear passenger side wheel bearing today. I’ll test it for couple weeks once I get the car back next week.

Baldur!

Thanks for keeping us updated, fingers crossed for permanent fix!

Adi-Benz

Mercedes Benz brakes also skim the rotors so that rust is not built up/debris, usually in cases when it's raining and you haven't hit the brakes for a long time, so when it does come time to stop, you won't have any issues. Don't know if every model does this.

thwgw24

The noise is still there after they replace the wheel bearing. They are going to check all the brake parts again, possibly caliper piston.

Baldur!

Thanks again... I'm going to change the tyres tomorrow and the next step will be to get an appointment too (I want to do it after changing the tyres to know if the vibrations problem is still there).

thwgw24

The technician took all the brake parts apart and lubricate them. But it wasn’t just lubricanting the the brake parts. The rotor we have is a 2 piece rotor and the rotor hub is thinner compared to a regular rotor. There’s a set screw that holds the rotor onto the hub and you gotta hand tighten those and not use a power tool. If it was tighten with a power tool it can cause the rotor to sit in uneven onto the hub. Same goes when putting the wheel on the car, not suppose to impact the lug nuts on others it might cause the same issue of the rotor not sitting evenly onto the hub. Just had tight the lug nuts then torque them to spec.

Baldur!

Thanks! So, was it the root cause and now the noise is not there? After changing the tyres I went through bedding process (however, I'm not sure how it works for rear brakes) - afterwards I already had 2 cases when I heard the noise , but for the time being vibrations problem is gone.

thwgw24

Just got the car back over the weekend and it wasn’t making the noise. I’ll update if it comes back again.