Odd sound, with sound clip!

[epapp]

This funky sound/'whirring' comes from the engine area, and it wasn't always there.

'99 and when I bought the car last summer, this noise was not there. I began to notice it slowly develop. It is still there with the acc belt off. Its now been like this for about 5 months.

The sound is always there, clutch in, clutch out, all gears, it is just MOST noticeable in 5th at ~65 mph (2700-2900). I know it is suspect in that RPM range to be variocam. But the sound is also there at 800rpm as well as 5000rpm.

If I keep a constant speed, the noise will be 'faintly' there, and when I alternate between on the gas ~75% and 0% in 5th gear on the freeway (hear recording), you can hear it whines mostly under load. It will also faintly whine when decelerating.

I have suspected a few things, but dont know how to troubleshoot them (short of pulling them out to visually inspect):

-oil scavenge pumps (anyone know if they sound like this/ spin this fast)?
-tranny input shaft
-clutch throwout bearing (I think these cars are setup such that the TOB always contacts the clutch plate

I'm not really suspecting the IMSB, given I've checked the oil/filter a few days ago, and with 5000mi on the oil since last year when I bought the car/changed the oil there are no obvious metal chunks/dust. It also doesnt appear to ever have leaked out of the transmission and engine mate/isnt leaking now, all is pretty clean down there.

Anybody know what else rotates around this audible speed in the engine? Noise is definitely tied to RPM and not speed.


https://drive.google.com/file/d/0BzgVZQpuS7NdVmJmUmRoczJJM3liNGdnZDBiOGtEUWx6cmow/edit?usp=sharing

[Shehadehd]

Have you tried putting a stethoscope to different parts of the engine to see if you can pinpoint a general vicinity?

[epapp]

Yes, definitely.

But I don't have a lift so I can only get at the front of the engine to probe while its running (not going to start it on jack stands).

I feel that someone on here has heard something similar, with all the people that take apart engines around here.

Is there anything I missed that spins about ^^that speed, based on what you hear? When I get home I'll run the recording through a FFT in matlab and find the frequency of the sound in the loudest area, and if its a bearing, I might be able to determine which one based on the ball passing frequency of each bearing in the engine....ideal** ball passing frequency that is..

EDIT: the frequency is ~2700-2800Hz, at different points in the recording (engine RPM is different at somepoints). I guess this means its most likely tied to the crank, unless the cams/scavenge pump turn 1:1 with the crank after all the different ratio changes?

[epapp]

I'm starting to think the sound is from the transmission. Anybody have any experience with this kind of sound from the transmission?


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[katanihouse@shaw.ca]

I had a whining sound coming from my engine that turned out to be loose spark plugs have you checked those?

[Nine8Six]

dude the sounds mine makes.... chains slappings, engine knocking & ticking here and there, random low and constant freq (woom-woom-woom, likely bearings, pulleys), drone, vibrations, different ambient temp/humidity = different exhaust notes, different gas, different noises and also performance ratios lol

all good and fun until it breaks for real here. not going to open it up like I did with dad's TV when I was 6 (was convinced little people were stuck inside of it)

[epapp]

I know, I know...despite passengers calling me crazy in the early stages of the sounds, ~4 months ago, they now can easily hear what I hear.

katani, I replaced the sparkplugs last summer and torqued them, but I haven't checked them since. I suppose next time it is up in the air I will.

986, I just switched to redline 0w-40 last night and this mornings commute was wonderful. All the minute sounds and startup clatter are gone, and it just feels (and definitely sounds) 'smoother' up to redline. Maybe you should switch?

Well, eventually something will fail, or the sound will go away.