2008 W204 C200k Sound deadening

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C Class
Posts: 31
Joined: Sun 16 Dec, 2012 11:24 am
Model you own: w204
Region: Tasmania
Location: Melbourne

2008 W204 C200k Sound deadening

Post by stefcep » Sat 29 Sep, 2018 12:49 pm

The more I look around this car the more short-cuts and cost cutting I see even compared with my previous W202. One of the consequences is excessive road and engine noise.

The boot has a plastic spare tyre well. There appears to be no sound deadening at the front wheel arches. The drivers side rear wheel arch has sound deadening over it but not the rear passenger side that i can feel. (Haven't removed the covers yet)

i've ordered this to go over the tyre well and the boot and wheel arches:

http://www.carbuilders.com.au/sound-dea ... tage-1~413 . Its a dynamat equivalent- stick on butyl with an aluminium on top. Peopl say only need to cover about 30% of the area but i'll have enough to do the entire well.

i've ordered this to go over the top of the above:

http://www.carbuilders.com.au/acoustic- ... tage-2~725.

I ordered this for my son's Mazda6 which I will test on my car as well


The engine firewall that goes frm one side of the car to the other is actually several pieces held together by plastic screws ( W202 was one piece) and thinner. In the W202 i suspect that it also stiffened the chassis. The W204 has a meal support bar bolted to each side shock cover.

I decided to order some some engine side firewalll sound deadener to place over the existing one using the same holes with longer plastic screws because it probably won't stick:

https://www.ebay.com.au/itm/14248615847 ... .S1.R1.TR2

I may stick them back to back for double thickness if they will fit.

I'll post back and see what if any difference this makes.

Mercedes Demigod
Posts: 5948
Joined: Sat 12 May, 2007 2:21 pm
Model you own: w204
Location: Melbourne

Re: 2008 W204 C200k Sound deadening

Post by Ivanerrol » Sun 30 Sep, 2018 10:40 pm

Check some of the overseas forums on sound deadening for W204's. It's a very common compliant.

I sound deadendddd my W202. Made a big difference. Given up on the W204.
Too be fair. On smooth roads the W204 is relatively quiet. But nowhere near as quiet as the W202.

If you have the drop down rear seat option on your W204 - you may as well have a window open with these in the down position.

I took my W204 from Melbourne to Noosa return. Before I left, I stuffed the spare wheel well with sound deadener. Didn't make much difference. You will need to do the rear guards inside and out, Rear parcel shelf.
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C Class
Posts: 31
Joined: Sun 16 Dec, 2012 11:24 am
Model you own: w204
Region: Tasmania
Location: Melbourne

Re: 2008 W204 C200k Sound deadening

Post by stefcep » Sat 13 Oct, 2018 1:36 am

OK so I completed this today.

I got measurable and subjective improvement.

At idle: Before 61-62 DB After: 56-57 db

On the Calder at Taylors Lakes (terrible rough road) at 100 km's per hour Before 73-75 db After 68-72 db.

I used the butyl-aluminium deadener ( "dynamat") on the plastic wheel well and the metal boot floor. This reduces "resonance", but it does NOT make the car quieter-it just changes the "character" of the noise. I put the standard boot cover over the spare wheel and then the mass noise boot liner-this is some mass loaded vinyl on top of foam and this is what actually cuts sound out. On top of that is the genuine MB cargo tray.

I used more butyl on the front quarter chassis metal under the guard and the inside of the guard as well. I covered the front wheel arches plastic covers with the mass loaded vinyl sheets. Did the same for the rear wheel

Covered the rear parcel shelf in the boot with the carpet underlay-it doesn't stick well to the painted part and its not made to stick upside down. Used it on the inside wheel arches, plus eunder the rear seat and the back of the rear seat. I don't hear any significant noise from the rear now. My seats do not fold, and this makes a difference having driven examples with he fold down seats even when they were not folded down. ( I noted the same with Lexus IS350 i also test drove- the older ones with no folding rear seats are super quiet, more than the current new ones with folding seats)

The firewall engine bay insualtion I doubled up and just fitted in front of the firewall behind the engine on the passenger side and behind the frewall on the driver side. I can barely hear the engine. BUT I'm not convinced it fire safe, so its out.

I've realize that even though the tyres have 90% tread, they were made in week 4 2013, so I'm sure they are louder than they were when new and don't help.

I now hear a fair bit of wind noise from the door mirrors

Overall for about $350 I'm happy with the result. One point: People seem to thin that "dynamat" block sound-it doesn't. You need a layer of de-coupled mass-loaded vinyl or the carpet underlay over the "dynamat" to block sound. Of course all this adds weight.

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