tategoi

Every morning when I start the engine, there is this rumbling sound that follows after the engine has started. Its like some serious vibration, like gear box has come loose. This only happens at cold start. Any of you also experience this? Is this normal? What rumbling sound is that?

jstaneff

I noticed something similar yesterday. I was driving slowly, about a mile from home and the temp was at maybe 60 C. The light turned green and the two hotshots on either side of me took off. Well, I rolled through the intersection, then floored it. Um, quite a rumble, and those two cars were left well behind.

Normally on a warm engine, you can't hear the car. My wife tells me that she can't hear it at all when I park it in the garage, and she has super-good hearing. But on a cold start, it's fairly loud.

My guess: normal. It's only for a short time on start up, enjoy it!

RickP330

I think there is alot of issues with the cold start on these engines. I just ignore it for the first few min and its fine....
RickP

Sanjuro Makabe

same thing every morning...after about 45s it becomes stable...I use that as a sign that I can start driving hah

aprince2die4

I get the knocking/rumbling every now and then just for a few seconds tho on cold starts...

akbro93704

My exhaust/tips make a 'subtle popping' sound at cold start, and sometimes the engine starts shaking during the warm-up too. It's normal, although it shouldnt be like this.

tategoi

Mine lasts only a few seconds, 10 secs max, and only at cold start. If I turned off the engine and re-started it half-an-hour later, there is no such sound anymore.

I was told it got to do with secondary pump. W204 comes with one. You know what is that?

johff

My car is a 2008 C 300 4 MATIC Luxury (Canada)

Yes, mine is the same when the engine is first started from a stone cold...the engine rumbles and the exhaust shakes and vibrates for a good few seconds (like a diesel truck)...

Anyway, I have a rumbling or gritty sound from the engine and/or exhaust when I am going at 45 mph at 1500 rpm. It's a an abnormal rumbling noise when the engine is laboring at that engine speed...

jeyhun77

Me too. At first it was a problem and reported it to the benz dealership. My service manager said it was normal on the new Cs.

451/443=EW

I havnt had any noises, its a 09 C350 but it only has 1500km on it. How many K or M you guys have? How cold is it in your area? Cars inside or out side?

Mine is also underground, and even in cold temps is wont get below freezing underground. So maybe thats why I have had an issue ????

tategoi

I have should cross 1,000 Km today Over here all year round its around 30 degrees Celsius/86 Fahrenheit both inside and outside In cold start I mean starting the car after leaving it overnight or after a few hours.

RickP330

I'm not sure if my car has gotten better or I'm just ignoring it now. but all seems okay...
RP

Les-10

Know that feeling!

RickP330

No, if you listen close it's still there. I've just learned to ignore it
RP

angeloxnet

i experience this everyday (now that its winter)
rumble sound (even more so, because of my x-pipe) but like others have stated it goes "stable" after 30 to 45 seconds, and I too use this as a sign "ok lets go"

C300Sport

Well now that it seems obvious this is "standard" for the W204, I would like to know what actually causes the sound. It is too easy for MB to simply say it is normal without identifying what it is.
Has anyone gotten an explanation as to what is actually causing the sound?

Moto_Guzzi

I usually walk around car while idling in garage after a trip to listen for any problems, none so far.

But on a cold start, I start the car with me outside, and to me it sounds like a valve opening/closing in the exhaust system, or from somewhere, then it suddenly quiets down.

RickP330

The best I could do for an explanation is someone here suggested that it has to do with the variable valve timing and the lack of oil pressure on start up. Apparently there may be some check valve to hold oil pressure when you shut off the car that may leak down, but it's not clear why this dosent happen when the car is totally cold.
RP

Bobby204

Dealer said it's the smog pump

albert101

I have the same problem. Car rumbles and wiggles like crazy during a cold start. I let the car warm up for a few mins and by the time I'm a few blocks away from the house, its all gone. My BMW did the same during cold starts so I'm just inclined to believe that this is just a cold start characteristic.

tategoi

What is a smog pump?

Albert, mine only last a few seconds. There was no such rumble on my E60 at cold start.

Star & Laurel

"Smog Pump" is the secondary air pump mentioned earlier. The name came about because it was first required for california emmissions. Now all US cars come with california emmissions and are equipped with "Smog Pump" / Secondary Air Pump. What this system is doing is there is an electronic air pump that injects air into the exhaust before the cat. Apparently this fresh air helps the cat to be more efficient during the initial warm up of the cat. You will see the air pump nested right in the middle of the "V" on the V6. Pop up the front engine cover and you will see it right in the middle.

evanswan

me too and dealer said it was some kind of pump.
should a 42k car be starting like this. Mercedes is pissing me off. 2nd one and still issues. Any service bulletins or replacement info. They need to fix this.

Carsy

Is it only US complience cars that have smog pumps ?.This information should put everyones mind at rest. Just blame Arnold