Hello
(I have a second post regarding alternator problems, here's my other recent issue)

I have some rattling/chattering/gurgling coming from the engine compartment when in idle.
- 2004 Cooper
- non-S
- 40,500 mi
- auto CVT transmission

Observations:
- sounds are pretty consistent in terms of frequency per second
- started about 1.5 months ago and was intermittent but is now pretty much all the time, though once in a long while the car will not have the noise when idle
- sound goes away around 1500rpm, whether driving or parked and revving (whether in P, N, R, D)
- belts seem OK, but I have not checked tensioners
- does not sound like a loose bolt, but I cannot be sure (since sound goes away after 1500rpm)
- on the rare occurrence when the car is not making the sound, I can cause the sound to happen very briefly by shifting gears or by turning the steering wheel (let's say I'm parked), but it is not 100% reproducible in this manner, but as I was playing around with the steering or transmission I was able to cause the chattering to happen for about half a second or so - this makes me think it may be related to some belt...
- the rattling/chattering can be felt on my shifter ****, meaning it's some part tied to the drive-train/tranny perhaps

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At first I thought the sounds were coming from lifters tapping, so I tried some fuel injector cleaners (cheveron techron in gas tank) and seafoam into the engine oil. I have not yet tried Seafoam into the vacuum/PVC lines yet.

Any thoughts? My searches on NAM mostly discuss manual transmission cars and clutch related observations, so I haven't found too much info yet.

 

Stick your head by the driver's side wheel well, do you hear it louder? If so, it's your trans, and I would recommend a flush. If you don't hear it any louder, listen for it by the exhaust, if it becomes louder there, I would suspect the power steering pump.

 

I forgot to mention where I heard the sound the loudest.

Yes, the sound is loudest when I place my ears near the alternator area. I was trying to do some reasearch on sypmtoms of a failing tensioner or idler pulley or water pump but found most pointing to squeals and not ticking/chattering.

I thought about the transmission as being a possible culprit, but then since the sound consistently goes away at 1500rpm it makes me think it's related to the engine and not the tranny... however, I have not yet had a transmission flush, so that's a good idea.


NOTE: I just changed out my alternator this past weekend for a different issue (battery light came on, battery was fine but was not charging - replacement of alternator fixed the issue) - I did _not_ change my belt because when I inspected it there was no stretching, no cracking, and no glazing.