Help me diagnose a high RPM whine
 

The Excursion in my signature has developed a loud whine at high engine RPMs (>2500rpm). It sounds like turbo whine, but it is much louder, and has a bit of a metallic sound to it, but still very high pitched. It is somewhat intermittent above 2500rpm, but is becoming more common. Here's what I know about it:

1) Turbo has zero in/out play, and barely any side to side play.
2) Boost is as good as it ever was - 23psi common in 60h tunes - and is not affected when hearing the sound.
3) The whine will occur even during coasting downshifts that bring the RPMs up above 2500.
4) Serpentine belt was new in December, 2010, and is the OEM belt.
5) I replaced the idler pulley a month ago, as the old one seemed have a little play. The new OEM one has exactly the same amount of play, though, and the sound was not affected.
6) The sound appears to be coming from the driver's side of the engine compartment. Unfortunately, that's where both the 6637 intake and the alternator are.
7) Alternator was replaced in April, 2011, with one from Autozone.

Any ideas? As I mentioned, this is getting worse, and I need to get it figured out and resolved.

Mark

sounds like a bearing to me. try taking the belt off and spinning the alternator by hand and see if you hear the metal sound

I'll try that again, but it felt fine when I had the belt off looking at the idler pulley. I don't have any way of spinning the alternator at the 6000rpm it hits at 2500 engine rpm. I hate to, but I might have Autozone warranty it, particularly if everything else is ruled out.

Mark

Had the same thing happen to me on my 82 bullnose a few years back... replaced idler... then alternator, then fan clutch... still no luck... so i lived with it for a year or so until my ps pump went out. Replaced it and the whine went away.


Xtof

That's what I'm afraid of. Got any great ideas as to how to replace the right thing the first time? The alternator and PS pump are so close together, I could never identify the sound source by location alone. Was your PS whine *really* high pitched? Its pulley is about the same size as the crank pulley, so I'd think it would whine at a lower pitch than the alternator, but perhaps not.

Mark

It was a really high pitched squeel. It wasnt really related to the pulley per say as much as the inside parts of the pump that were failing.

Xtof

Well, the alternator spins smoothly, but if I can feel play in the rear bearing by moving the pulley up and down. I can feel the shaft move up and down 1/16" if I put my hand on the back of the alternator. Is that normal? It doesn't seem right...

Mark

i dont think it should move any. thats play in the bearing

Yeah, as I was fooling with it, I realized the rear bearing cap was... gone. I've got the new one in hand, and am installing it now.

Mark

[quote=ScaldedDog;12303193]The Excursion in my signature has developed a loud whine at high engine RPMs (>2500rpm). It sounds like turbo whine, but it is much louder, and has a bit of a metallic sound to it, but still very high pitched. It is somewhat intermittent above 2500rpm, but is becoming more common. Here's what I know about it:

1) Turbo has zero in/out play, and barely any side to side play.
2) Boost is as good as it ever was - 23psi common in 60h tunes - and is not affected when hearing the sound.
3) The whine will occur even during coasting downshifts that bring the RPMs up above 2500.
4) Serpentine belt was new in December, 2010, and is the OEM belt.
5) I replaced the idler pulley a month ago, as the old one seemed have a little play. The new OEM one has exactly the same amount of play, though, and the sound was not affected.
6) The sound appears to be coming from the driver's side of the engine compartment. Unfortunately, that's where both the 6637 intake and the alternator are.
7) Alternator was replaced in April, 2011, with one from Autozone.

Any ideas? As I mentioned, this is getting worse, and I need to get it figured out and resolved.

Mine does it a little and I think it may be the power steering pump- Mike

Did you ever figure this sound out ?

I did, and sorry for not posting the fix years ago. The reman O'Reilly alternator had lost it's bearing cap in back, and the rear bearing failed. It was easy to see and feel with the belt off, but not easy, otherwise. A new alternator resolved the problem.

Mark

Why I’m generally not a fan of reman parts

My truck has a sounds that starts around 1900 rpm under load. Been chasing its, here's mine

I can't tell from the video, but have some questions: Is it consistent above 1900rpm, or does it "chirp" or elsewise make an intermittent sound above that rpm? Does the pitch change with rpm?

Mark