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Weird underbonnet 'buzzing' at speed

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Old 03 June 2001, 05:20 PM
  #1  
spider
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OK, I realise sounds aren't easy things to explain in words, but I'm stumped by what's making my Scoob buzz!

When taking her over 90 mph (Autobahns only! ) I get a noise from under the bonnet that sounds like a swarm of angry bees!! What the heck is causing it??

Before any clever-dick says it's the engine/exhaust, I don't think so.

The noise only starts over 90 and is not related to engine revs (a coasting test on an old airfield proved this - it's definitely speed-related).

Seems to be worse when we have windy weather, so I guess something is 'flapping in the breeze'?

I've poked around under the bonnet and can't find anything obviously loose or rubbing. Checked the brake pipes as per SIDC FAQ, but they don't seem to be touching anything.

Any ideas (other than turning up the stereo?)

Thanks in advance,
Steve
Old 03 June 2001, 05:25 PM
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Ian Cook
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What Model Year ?

Sounds like a heat shield broken ! Either the turbo or one of the exhaust ones !
Old 03 June 2001, 09:18 PM
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GranTurismo
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Hello,

What about the waste gate solenoid?

FAQ says it can become noisy, clicking? especially if getting boost to overtake?

Could be a relay type noise?

The heat shelid thing is noticable maily when you stop. if you rev the car it rattels on the over-run.
Old 03 June 2001, 09:32 PM
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boomer
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spider,

i had a similar noise on my Renault 5 GT Turbo several years ago - and it drove me mental!! Just like yours, it seemed to be speed/wind related and not related to engibe revs. It also happened at a similar speed (er, i expect, er, officer).

In the end, it turned out to be my windscreen, or rather the seal/surround - because when i had it replaced (a long story) the noise went away.

Check your screen and fitting!

mb
Old 03 June 2001, 11:28 PM
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spider
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Ian, MY98 UK saloon. Must admit I hadn't checked the exhaust or turbo heat shields as I was poking around after a run and didn't want to toast my fingers! I'll have a look tomorrow morning.

GT - don't know about the solenoid. The noise increases with speed over 90, but disappears entirely below 85. Perhaps I have a car with a speed conscience?!

Boomer - crikey, I hope not! The last thing I want is to be picking bugs out of my teeth when I get to work. I'd ride a bike if I wanted that!! Ta for the pointer though - I'll check it out.

Thanks guys,
Steve

[This message has been edited by spider (edited 03 June 2001).]
Old 04 June 2001, 12:11 AM
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WAYSIDERS
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I had a strange buzzing noise coming from the dashboard area at high speed a few months ago. It got louder and more buzzy as speed rose. Try popping the clutch, let the engine revs drop: if the noise doesn't change it's not engine-related.

My buzzing turned out to be dry leaves which had found their way through the ventilation system!
Old 04 June 2001, 10:06 AM
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healeyb
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What a coincidence, I've just experienced the very same thing on my STi. It's definitely speed related, and I noticed that it came on at lower speeds going under bridges on the A-bahn (also doing a lot of driving in Germany). I can't find anything loose except my rear foglight, but the noise did sound like it was coming from the windscreen area, though it's hard to tell. I'm going to get my windscreen seal checked and see what happens. This problem seems to have come on after the car has been kept at the airport for a week. I can't see any signs of anyone trying to break in, though perhaps it's worth checking again. Keep us posted on what you find, and I'll reciprocate.

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Old 04 June 2001, 10:17 AM
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chiark
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It couldn't be something stupid like the alarm mounting bracket could it? These are known to fail...
Old 04 June 2001, 02:59 PM
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spider
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Thanks guys, some more areas for me to check tonight.

Waysiders - that's a good point. My car is often parked under trees overnight and is covered in leaves/pine needles in the morning - looks like it's hoover time!

When I find the source, you'll all be the first to know!

Cheers,
Steve
Old 04 June 2001, 11:49 PM
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boomer
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Red face

spider,

if it is your windscreen seal, then swallow hard! I had my screen replaced last week (crack caused by something hitting hard) and they had to fit a new top plastic "strip". This alone was GBP29 PLUS VAT - dunno whether you could get yours done as a windscreen insurance jobbie (if that's the problems)?

mb
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