Help diagnose this sound/rattle from video

[oregonmon]

Hey all,
Just did my first oil change and dropped in a new K&N filter too. But for the problem and it did start before the oil change. Driving around yesterday, at idle and standing still, I noticed this rattle sound. It would go away sometimes when I revved it up a bit. Then today with the engine lid open I could hear it more. Sounds like metal of some sort but here's a video to maybe help. It sounds like it is coming from the fan area, but not sure.
Thanks.

[jester911]

Can't seem to play the video.

[oregonmon]

Seems to work for me. When I watch the video it's even hard for me to discern so it not be to easy to pick out. I've been listening to a lot of exhaust clips on the board and it almost sounds like a raspy sport muffler (mines stock). Oh well, give me your best.

[mca]

Hmmm.... certainly wait for additional people to chime in.

IMHO I would not drive it until I could confirm it wasn't a failed chain tensioner.

As I understand it, the noise tends to "go away" with higher revs.

Nice work on posting the video - technology is pretty awesome these days.

[dbrisson]

Could something have fallen between the metal flashing and the lower pulley? Alternator bearing? Maybe disconnect the belt for a sec (not long ie air flow) and see if the noise is still present. That would rule out alt and ac bearings.

[rusnak]

It's hard to tell what that is from the video. I don't think it's a chain tensioner because it would sound more like a chain being dragged out of a trash can. My first thought is to disconnect the AC compressor because it sounds like a rattling compressor clutch. Next would be to check your fan belt tension because it could also be your cooling fan moving back and forth on the alternator shaft. Sometimes when there are fit issues with the fan belt, the fan can clunk back and forth.

I think if you have a magnetic retrieval tool, you should also fish around in the well that the crank pulley turns in to be sure that a spacer didn't fall down in there and get trashed.

[oregonmon]

Originally Posted by rusnak

It's hard to tell what that is from the video. I don't think it's a chain tensioner because it would sound more like a chain being dragged out of a trash can. My first thought is to disconnect the AC compressor because it sounds like a rattling compressor clutch. Next would be to check your fan belt tension because it could also be your cooling fan moving back and forth on the alternator shaft. Sometimes when there are fit issues with the fan belt, the fan can clunk back and forth.

I think if you have a magnetic retrieval tool, you should also fish around in the well that the crank pulley turns in to be sure that a spacer didn't fall down in there and get trashed.

I do have the Carrera upgraded tensioners, those are not known to fail right? But your assessment regarding the type of sound seems right. It's a more tinny/thin metal/exterior sound. I listened to a clip of a failed tensioner and it was different. Thanks for the tips. "rusnak" Only other person with that last name I've met besides my good friend in Austin.

[haycait911]

maybe try a long screwdriver held against different areas while holding the other ( dull ) end against your ear. or a mechanics stethascope would also work in a pinch.

listening again, it almost sounds like an exhaust leak.

[oregonmon]

Yeah that's what I was trying to say in my earlier post. But in person it does not. If you separate all the other sounds/compression from muffler and just tune in on the rattle that's where the problem is. Easier said than done, and keep in mind I'm no mechanic.

[PatrickB]

I would say its the beginning of a failed alternator bearing... Especially if it tends to go away after the engine is warmed up... If the noise bugs you, change it out.
Check the output of the alternator too. Alternator ever been changed out or rebuilt? or are you running with the OEM unit

Mine sounded much worse, and I kept driving it until the alternator output began to falter. Keep in mind, mine was the original 22 year old unit with 160k miles on it when I replaced it!

[oregonmon]

Originally Posted by PatrickB

I would say its the beginning of a failed alternator bearing... Especially if it tends to go away after the engine is warmed up... If the noise bugs you, change it out.
Check the output of the alternator too. Alternator ever been changed out or rebuilt? or are you running with the OEM unit

Mine sounded much worse, and I kept driving it until the alternator output began to falter. Keep in mind, mine was the original 22 year old unit with 160k miles on it when I replaced it!

Not sure of the history of the alternator. I wouldn't doubut it's the orginal. Car has 139k miles. Anyway to be a little more certain that is the problem?

[PatrickB]

Get someone local that knows more than you & I do to take a listen!

Stethoscope to the shroud near the alternator with engine running may be of help... Like I mentioned before, if this sound lessons after the car is warmed up, it's a pretty good chance it will be a bad bearing in the alternator! No worries, as I drove mine like this for 2 years before replacing the alternator!

[Paulporsche]

Aside from the rattling, unless you were revving the engine, that idle hunting usually indicates a too rich mixture.