Abnormal rattling sound coming from motor/engine bay

[Focused]

Hey guys,

Proud owner of an MS3 with 8,600 miles on it.

Haven't had any real concerns with it up until now. About a month ago (give or take) I heard this rattling sound from from my engine at idle. It's kind hard to describe...best I could say is it sound likes an empty can being kicked on the street. Better yet, it sounds like something clacking back and forth again something else (metal-on-metal however).

The sound is not consistent either, meaning while at idle, it's NOT sounding off at the same rhythm of the motor.
It's loud enough that one would notice it from inside the car, moreso with the windows down. Again, very obvious difference in sound from the engine idle and the rattling thing i'm hearing...

Additionally, there have only been 2 events/nights (last month and last night) in which this sound was heard. This sucks because when I bring it into the dealership tomorrow, it probably won't sound off, and they will not be able to hear it.

Any clues? (huh)

Lastly, how does YOUR engine sound when shutting it off? Does it have a smooth shutdown or a rough one? Do you hear any mechanical pieces coming to a stop or is it quiet?

Mine's relatively rough...and I hear what I think is the crankshaft slowing to a stop...it's pretty loud.

Anybody else experience that?

Thanks in advance for any replies.

 

[gsrtype1]

yeah mine kinda shakes when im shutiing if off could just be a soft motor mount, but never the sound your talking about. I would check the motor mount!

 

[javanc]

Do you happen to have the MS CAI installed?

 

[OKCMS3]

Check your hood prop. Mine seems to have a lot of wiggle room in its stored position and I've often thought that I can hear it vibrating.

I wouldn't characterize my shutdown as rough, but it certainly isn't the smoothest of all the cars I've owned either. It's similar to that of an S2000 I used to have, so I've always attributed it to the high performance nature of the motor.

 

[jeg0024]

yeah mine kinda shakes when im shutiing if off could just be a soft motor mount, but never the sound your talking about. I would check the motor mount!

Yes, please, check all your motor mounts to be sure there all tight. I dont wanna see another thread about a MS3 motor ending up dragging the ground again

 

[ReD Rocket]

i had a sound at idle a few times... i have 10xxx. miles on mine.. souds like a through out bearing... next time you hear it.. try pushing in your clutch to see if it goes away... my question.. is it covered by waranty.. or even b etter... where do you get a clutch upgrade

 

[Focused]

Thanks for all the replies so far, fellas.

The sound is far more "serious-sounding" than a throw-out bearing (although I have that sound, but that's no concern), or the hood prop.

Sounds almost like it's something internal...something in the motor that's clacking back and forth. Again, though, it's shows absolutely no consistent rhythm or pattern. Comes on for 1 seconds...goes away for 5 sec....comes back for 2 sec....goes away for 1 sec...comes back for 2 sec....goes away for 10 sec....and so on. No pattern whatsoever.

And there've only been two events...

I've got an appt with my dealership manana, so I'll bring it up to them and see if they've encountered such a problem before. I'm sure the sound won't be there tomorrow during check-up (the problem's never apparent when you need it to be, ha!).

If they don't know anything, guess I'll just have to keep on driving it and hope nothing bad happens. I've come to learn car problems like this often are smaller than they seem to be. I'm hoping it's one of those times...

Oh, and I'll have the mount checked again by them while it's there. It doesn't sound like a bad/loose mount by any means. And I don't feel any irregular movement while shifting or anything, so i'm thinking it's not. But better safe than sorry, of course.

Thanks again. Keep y'all updated.

 

[Betelgeuse]

I guess you didn't read all the replies. Do you have any mods? MS Cai? I've heard the CAI can cause a rattle.

 

[Focused]

Or maybe I just missed that one? Sorry, sir, I'm only human.

No, I didn't have a MS CAI or any other mods when this sound occurred.

As I said in my previous post, it sounds far more "serious" than a rattle, as if it's INTERNAL.

 

[Focused]

Oh, and just to update:

My appt. didn't happen. Was just one of those days, and things didn't work out as planned, so I had to reschedule for next week.

While I'd really like to know what it is, I'm not going to worry about it and baby the thing 'til then, 'cause chances are they won't be able to replicate the sound, and therefore won't offer any real help.

 

[Betelgeuse]

Could just be a heat shield rattle since it's not to the rythm of the engine. I'd let it idle, pop the hood and try to figure out exactly where it's coming from. It could be something really simple.

 

[Focused]

Yeah, I'm hoping it is...often times these things are smaller problems than they seem.

But as I've mentioned many times, it sounds INTERNAL. It does not sound like a heat shield, or anything external to the motor. The two times I've experienced it, I've tried finding the source of the sound, but with the engine idle, it's hard to pinpoint. It really does sound as though it's something inside the engine itself, and not just in the bay.

It ain't running bad by any means, so I'm going to keep driving it the way I do, and pray it's still under warranty if something happens! ha...ah well. the joys of car ownership.

Thanks again, y'all.

 

[Euphorism]

what octane gas are you using?

 

[Focused]

93...

 

[Hikaru9]

Perhaps the mechanic at the Mazda dealership left a tool inside the engine bay like they did to my MS3. ^_^;;

 

[Focused]

Ouch...2 points for that dude...nice one. Hope that didn't cause any harm.

BTW, I think I may have found the culprit - a possibly outgoing throwout bearing. My throwout bearing is relatively loud to begin with at idle, however, as I listened closer earlier this evening, the low sound of the TOB sounded like the rattle in question.

Matter of fact, the loud/abnormal sound came back while idling for a split second earlier, and this time I pressed in my clutch to see if it had anything to do with the clutch. Now, the sound did not IMMEDIATELY go away with the depressing, but it simply faded away, as though following my clutch action.

Weird, but I'm thinking that's the source of the sound. A noisy TOB.

No biggie, if that's the case! As long as it ain't an internal issue...