Another update. After driving it today, nyah, after driving this thing for over 4 years you can tell when something just doesn't quite sound right, and something definitely sounds just a little different. I'm done worrying about it. I now know it lies in the s/c and it still runs really well. The season is just about done, it gives me more incentive to dive into my plans to pull it, service it, change the pulley, do the octopus etc. and whatever else. I can always send it out and have it gone through once it's off and know it'll come back with a fresh bill of health, warranty, and ready to give me ... more power!!

 

It's been a year now, and being a noob on forums I don't know if I should just start a whole new thread or not.

This is all about my '04 XKR which is days away from turning only 80K miles. Anyway, nothing has changed with my "mystery whine" (or "whirr") except; 1, it's gotten a little worse. 2, I pulled the s/c belt a while back and drove it and it seems to still be there! (Surprising how well these still run and drive with that belt off!) So basically, my entire post here last year I was completely wrong and blaming the wrong thing. Apparently it isn't the supercharger after all! My apologies.

This damn noise is come & go, sometimes it's there, sometimes it isn't. Sometimes it's louder, others not so much, it's getting ridiculous. It doesn't follow any pattern like warm/cold, etc. It might do it right from the start in the morning, it might do it later in the day, it might go away, it might not, other days it doesn't do it at all! I wish I could describe it better, it's a much lower pitched sound than the supercharger, I'm thinking around 600 Hz @ 2000 rpm best I can tell, and changes pitch in sync with rpm. I know this sounds weird, but it sounds like a cross between the normal s/c whine at lower pitch, and air blowing through a fan! Of course, the one time it was doing it and I managed to stop in at a shop where I know someone, when he comes out to the car and I start it, it decides not to do it and sounds fine!

So now I start to wonder if it isn't more serious internal such as worn/disintegrating timing chain guides which worries me, or something as stupid as belt tensioners on the main serpentine belt! I highly doubt it's an alternator, charging voltages are on the money and I think it's way too low pitched. Also I think too low pitched to be like a power steering pump noise. I can't even rule out that it might even be originating in the transmission! The car still runs and shifts to perfection, but I can't help but think whatever it is, someone, somewhere has had some familiarity with the same thing going bad and making similar noises.

Thanks for all the previous replies and effort from everyone previously, and sorry in advance if I'm screwing this up and should be doing this on a new thread!

 

You might get off easy if it’s the CPU cooling fan. Mine would make a helluva racket when it was on its last legs. A loud fan squeal at times. It’s located under the cover near the right side of the bulkhead, passenger side on USA cars. New fans are about $100 from SNG Barratt

good luck, hope it’s not something internal.


Z

 

Go on Amazon and get a 20$ auto stethoscope... I couldn't believe I was ordering one when I finally did, but I find myself pulling the damn thing out pretty often. They are pretty remarkable when needing to zero in on a sound, rattle, click and tap.

Could be tensioners, power steering pump, alternator and or whatever else. Bearings...

Oooooh, the chase! Gotta love it.

 

^^
Can you record the sound and post it up here?