funny engine noises upon startup...suggestions?
Thread Starter
Newbie
Joined: Sep 2013
Posts: 7
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From: Indy
2009 C300 Sport 6MT, 2004 Forester XT 5MT
funny engine noises upon startup...suggestions?
Hi all! I'm a new member but have been trolling the site for a couple weeks - this place is a great resource!! 
I recently purchased an 09 C300 Sport 6MT. This is my first MB (first non-Japanese car I've owned,actually) and I've fallen hard for auto However, I've had a couple very minor issues since bringing it home which has made me somewhat paranoid 
upon starting the car, there's an immediate rattling/shakiness which always dies after about 10 secs at idle. I've researched this and found info about the bearings and wondering if this might be the culprit. However, upon startup yesterday, this shakiness was worse, the noise/vibration transferred to my steering wheel and the idle was low and rough. The headlights were dimming at this point as well (constantly on but the lights seemed to dim in and out in correspondence with the rough idle). No AC or audio on. Lights got brighter when I would give a slight rev. After maybe a minute I heard something loud switch on - sounding somewhat electric related as it was accompanied by a loud whining type noise. At this point the car was fine, back to normal and hasn't recurred after two more restarts at different times.
First thought was alternator but I wondering why it hasn't happened again, if this is the case? I'm planning on taking it in to either the MB dealer or one of the local European shops (have some great ones in my area) but I would love any suggestions as to what the culprit truly is - has anyone experienced similar, and if so, what was the issue?
Any feedback is truly appreciated - I'm not too savvy with autos and my fiancé is away on business (he's a car guy but also has never dealt with German vehicles)!!
Thanks in advance!
Andrea
I recently purchased an 09 C300 Sport 6MT. This is my first MB (first non-Japanese car I've owned,actually) and I've fallen hard for auto
However, I've had a couple very minor issues since bringing it home which has made me somewhat paranoid upon starting the car, there's an immediate rattling/shakiness which always dies after about 10 secs at idle. I've researched this and found info about the bearings and wondering if this might be the culprit. However, upon startup yesterday, this shakiness was worse, the noise/vibration transferred to my steering wheel and the idle was low and rough. The headlights were dimming at this point as well (constantly on but the lights seemed to dim in and out in correspondence with the rough idle). No AC or audio on. Lights got brighter when I would give a slight rev. After maybe a minute I heard something loud switch on - sounding somewhat electric related as it was accompanied by a loud whining type noise. At this point the car was fine, back to normal and hasn't recurred after two more restarts at different times.
First thought was alternator but I wondering why it hasn't happened again, if this is the case? I'm planning on taking it in to either the MB dealer or one of the local European shops (have some great ones in my area) but I would love any suggestions as to what the culprit truly is - has anyone experienced similar, and if so, what was the issue?
Any feedback is truly appreciated - I'm not too savvy with autos and my fiancé is away on business (he's a car guy but also has never dealt with German vehicles)!!
Thanks in advance!
Andrea
Registered User
Joined: Jun 2013
Posts: 499
Likes: 1
From: nowhere
2010 C300, 2013 C63 AMG
First off, congrats on the car! My 08 W204 used to do similar things, and many other people I know hear annoying noises on their W204s. From what you seem to be experiencing though, it does not sound like one of the common problems that I would have. Some C300s have a loose bearing, like you said earlier, which could cause it. As for the headlights, it seems as if that might be an electrical problem, which you should get checked out. It makes me think battery or alternator, but the whip noises just don't make any sense if it was one of those.
Definitely get it checked out at dealer, it might be that I haven't seen it since yours is M/T, but hopefully being 09, it might still be in warranty?
Definitely get it checked out at dealer, it might be that I haven't seen it since yours is M/T, but hopefully being 09, it might still be in warranty?
but it will be going in this week... fingers crossed!!
