Got a whine - alternator?

[New Duke]

There's an audible whine when I drive the car recently. It's so noticeable that I can hear it as much as my ridiculous air intake. Thought it might be interference coming out of the speakers but it's present even when they're off and sounds like it's coming from the engine bay.

Except that when I open the bonnet I can't really hear it, not enough to locate it, it's not obvious at idle. It's definitely louder when I'm driving.

Is it possibly the alternator with those symptoms? And is there any way for me to test it with a multi-meter etc? I don't appear to have any electrical symptoms, it all works fine. It's just that damn whine.

[casey]

Whine or whistle Haydn ?

Several people, including me, have suffered from almost invisible fractures in the 90 degree angled vacuum plastic pipes that plug into the intake bellows. There are 2 or 3 of these small pipes on the S1. When there is vacuum in the bellows, it caused the fracture to act as a whistle

Took me ages to pin it down!

[Lemon]

i've heard reports of another whine as well though this appears to come from the interior, specifically the passenger seat...

[13Black]

Need some audio recording methinks

Could be worth popping the AC belt off (17mm spanner, 10mm socket) to eliminate that and go from there.

[warpc0il]

Note that the speakers are never "Off", and neither is most of the head unit, when the ignition is On.
Just try pressing the CD Eject button, without switching the unit On.

It could therefore be electrical noise coming through on the speakers.
There's a couple of things you can try;
- switch the audio On and play with the volume; does the noise change? Sometime electrical noise disappears when the system is On and the volume on zero.
- pull the Audio fuse #11 in the passenger footwell

[New Duke]

Thanks for the suggestions guys. All appreciated and new to me. I do think it's a whine Malcom, but you've got me wondering now so I'll take her out again and have a another listen. Always nice to have an excuse for a drive I'll attempt to hook up one of my proper film mics in the car for some decent audio.

Need some audio recording methinks

Could be worth popping the AC belt off (17mm spanner, 10mm socket) to eliminate that and go from there.

Awwww maaaaaan, we just replaced that belt and pulley together Good shout though. Just to check, I can remove that belt and run the engine without harming anything right? (I wouldn't remove the water pump belt and run the engine, I'd assume things would quickly go pop)

Note that the speakers are never "Off", and neither is most of the head unit, when the ignition is On.
Just try pressing the CD Eject button, without switching the unit On.

It could therefore be electrical noise coming through on the speakers.
There's a couple of things you can try;
- switch the audio On and play with the volume; does the noise change? Sometime electrical noise disappears when the system is On and the volume on zero.
- pull the Audio fuse #11 in the passenger footwell

Excellent point thanks. I use an aftermarket headunit and it's also always 'live'. Will take that fuse out as the first step.

[13Black]

Correcto I don't have the AC compressor, idler pulley or belt on mine, it shouldn't throw up any codes. You can take it off without disturbing the main belt. Just be sure to check the tension before removing to get some idea of what's normal.

I assume the noise goes up and down with the revs, so perhaps a pulley bearing if it persists with the speakers off.

PS wtf are you doing awake at this time in the morning.

[New Duke]

Hehehe, asks the other guy up late. I'm booking a charity track day. Will post it up shortly!

Thanks for that. Will have a fiddle and see what's what. Yeah it matches the revs. At first it gave me rebuild paranoia.

[Lemon]

If it's an aftermarket head unit it is probably in need of a ground loop isolator.

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[New Duke]

Update:

I took out fuse 11 from the passenger box and ran it through the entire rev range a few times at varying pedal speeds. I'm convinced it's generally higher pitched than it used to be, but I can't qualify that so will park that idea for now. There's something odd happening from 7.5k RPM to the limiter though.

Raise the revs slowly and at that 7.5k point a high pitch whine kicks in, from somewhere near the pulleys or engine block. Raise the revs fast and at 7.5k RPM that sound is a squeak. A couple of times it sounded like the a belt was slipping or jumping (loud squeaks)... but I can't be sure. There's definitely something up in the engine bay. All this is when stationary. It's too loud when driving to pick out individual sounds. I'll still try to hook up a boom mic tho.

I then overheated it and the car wouldn't start (even at 2 degrees ambient)... so gingerly decided to call it a day after finally getting it started again and letting the PCM calm down and the stalling stop.

Next step I'll remove the AC belt as Nick suggested and test. Then I'll probably replace both belts anyway. The water pump belt I supplied for fitting in November was off the shelf at a motor factors, looked ancient and was a brand I don't recognise so maybe, hopefully, it's as simple as naff rubber. If that doesn't work then I'll have someone else check out the pulleys and bearings. We fitted the RRP pulleys in November too. Maybe they're just a bit noisier? Dunno.

If it's an aftermarket head unit it is probably in need of a ground loop isolator.

Thanks Stu, good shout. Have confirmed it wasn't that now. I've got some fancy active ground loop/ control boxes installed in the dashboard already with my aftermarket stereo

[13Black]

Squeal up top and overheating would probably suggest alternator/water pump belt stretching and getting loose enough to slip, perhaps?

Give both belts a tug and try and twist them 90 degrees by hand.

[New Duke]

Thanks Nick. Will have a tug and a twist

[13Black]

GO TO BED FFS

[New Duke]

Forgot to update this. Was indeed a belt slipping when pushed hard. A belated 5 points to Nick.

[13Black]

Whoa whoa whoa wadaminit WHOA

R u telling me

That 27p belts from 1976 turned out 2 b false economy?

I cannot brain this cognitive dissonance.